Light Earth Building: A Handbook for Building with Wood and Earth 9783035606454, 9783035606348

Table of contents :
Content
Foreword
100 Introduction
200 Building materials for light earth
300 Preparation of materials for light earth
400 Wet construction
500 Dry construction
600 Aspects of building construction and finishing
700 Planning and costs
800 Physical properties
Projects
Appendix
Sources and reference literature
Publications of projects
Index
Picture credits
About the author
Glossary

Citation preview

Light Earth Building

Franz Volhard Light Earth Building A Handbook for Building with Wood and Earth

Birkhäuser Basel

Dipl. Ing. Franz Volhard Schauer + Volhard Architekten BDA, Darmstadt, Germany www.schauer-volhard.de

Library of Congress Cataloging-in-Publication data A CIP catalog record for this book has been applied for at the Library of Congress. This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, ­reproduction on microfilms or in other ways, and storage in databases. For any kind of use, permission of the copyright owner must be obtained. Cover photo: Light earth external skin applied to battens on a new private house in Darmstadt, 2012 Translation from German into English: Julian Reisenberger Layout: Michael Karner Typesetting: Sven Schrape Lithography: Manfred Kostal, pixelstorm Printing: Holzhausen Druck GmbH, A-Wolkersdorf Bibliographic information published by the German National Library The German National Library lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at http://dnb.dnb.de. This publication is also available as an e-book (ISBN PDF 978-3-0356-0645-4; ISBN EPUB 978-3-0356-0648-5) and in the original German edition (Bauen mit Leichtlehm, 8., neubearbeitete und ergänzte Auflage, ISBN 978-3-0­356-0619-5) and in a French edition (Construire en terre allégée, Éditions Actes Sud 2016, ISBN 978-2-330-05050-4). © 2016 Birkhäuser Verlag GmbH, Basel P.O. Box 44, 4009 Basel, Switzerland Part of Walter de Gruyter GmbH, Berlin/Boston Printed on acid-free paper produced from chlorine-free pulp. TCF ∞ Printed in Austria ISBN 978-3-0356-0634-8 9 8 7 6 5 4 3 2 1

www.birkhauser.com

Content

Foreword

9

100 Introduction 110 Earth as a building material 120 Earth building methods

11 12

130 140 150 160

15 31 33 33

Solid earth construction – Frame construction

Building with earth – a historical overview Building with earth today? What possibilities can earth building techniques offer today? Building with timber and earth

Straw-clay and fibre-clay mixtures – Light earth

200 Building materials for light earth 210 Soil and earth

41

220 Fibres and aggregates for light earth

53

300 Preparation of materials for light earth 310 Preparation of clay slip

57

320 Preparing fibres and aggregates

66

330 Preparation of the light earth mix

69

340 Organisation of the building site 350 Ready-mixed material

78 80

400 Wet construction 410 Shuttered walls

81

420 Manual application

98

430 Floors and ceilings

107

440 Roof insulation

119

Soil formation and deposition – Cohesion – Soil texture – Soil identification – Testing cohesion – Testing slurryability – Sourcing earth for building Straw – Woodchip – Mineral lightweight aggregates

Weathering – Soaking – Drying – Mixing by hand – Mixing with an agitator – Mixing with a compulsory mixer – Consistency of the clay slip – Liquifying agent – The addition of lime Straw – Wooden aggregates

Spray method – Dipping method – Mixing in a compulsory mixer – Mixing proportions – Tempering

External walls – Internal walls – Formwork – Formwork systems – Walls with lost formwork – Compacting the light earth mix

Wattle – Stakes – Earth reels – Laths – Manual application onto lathwork Preparation of the timber construction – Earth reel floors – Compacted earth floors on sliding formwork – Floor infill on permanent formwork – Floor infill on supporting stakes – Suspended lath ceilings Light earth reels – Compaction behind sliding formwork – Infill behind permanent formwork – Infill on lathwork – Inner lining on lathwork

Content  5 

450 Light earth in building restoration

124

460 Spray application approaches

131

500 Dry construction 510 Light earth bricks and blocks

133

520 Light earth panels

135

530 Self-produced bricks and panels

136

540 Walls

142

550 Floors and roof inclines

151

560 Dry construction

154

600 Aspects of building construction and finishing 610 Protection of the construction

159

620 Plasters and paints

163

630 Two-coat lime renders (inside and outside) 640 Earth plasters

168 169

650 Windows and doors 660 Floors 670 Internal wall coverings

182 183 184

680 Technical installations and fixings

186

700 Planning and costs 710 Construction period 720 Cost and labour

187 188

730 Building codes and regulations

192

740 Design, specification and construction supervision 750 Self-building 760 Typical mistakes

197 197 198

Panel infill with straw-clay – Panel infill with light earth – Insulating wall lining of external walls – Internal insulation applied to lathwork

Brick-format products

Panel-format products Manual manufacture

Light earth masonry – Panel infill in half-timbered structures – Thermally-insulating internal wall linings – Stacked walls – Partition wall panel elements

Self-supporting floor slabs – Earth slabs and bricks for floor weighting Walls – Ceilings and roof spaces

Rising damp and splash water – Weather protection – Airtightness – Wood preservation and surface treatment Preparations

Earth plasters with sand – Fibre-clay or straw-clay plasters – Two traditional recipes – Paints and wallpapers on earth plasters – Ready-mix mortars – Requirements of earth plaster mortars

Timber wall panelling – Tiling

Water installations – Wall chases and anchoring methods

Labour – Tips for rationalising the working process – Professional contractors – Self-building Early earth building norms – Current norms – Planning permission and construction permits – Thermal performance – Building material properties

6 Light Earth Building

800 Physical properties 810 Thermal protection

199

820 Moisture/drying

209

830 Fire behaviour

221

840 Sound insulation

227

850 Airtightness 860 Absorption of toxins

232 232

Projects 1 Conversion and extension of a half-timbered house (D) 2 New private house with workshop (D) 3 Earth building settlement: Domaine de la Terre, L’Isle d’Abeau (F) 4 New youth community building (D) 5 Barn conversion (D) 6 House extension (D) 7 Cowshed and barn conversions (F) 8 Summerhouse (S) 9 Atelier (D) 10 Earth house in Maria Rain (A) 11 Historical renovation and extension of a listed building (D) 12 Historical renovation of a listed building (D) 13 Single-family home in Raisio (FIN) 14 Littlecroft, demonstration building for a research project (UK) 15 Sandberghof community-oriented housing (D) 16 Single-family home in Sweden (S) 17 Church in Järna (S) 18 Guesthouse in New Mexico (USA) 19 Prajna Yoga Studio in New Mexico (USA) 20 Single-family home in Wisconsin (USA) 21 Single-family Home in Carla Bayle (F) 22 Twenty houses made of straw light earth (F) 23 Conversion of a rural house in Normandy (F) 24 House rebuilding in Haiti 25 Schap 2011 – Primary school in South Africa (ZA) 26 Single-family home in Victoria (AU) 27 Private house in Darmstadt (D) 28 Single-family home in Kaipara Flats (NZ)

234 236 240 242 244 246 249 250 252 256 258 261 264 266 268 272 273 274 276 278 280 282 283 284 286 288 290 294

Thermal insulation – Thermal retention – Heat absorption and dissipation – Surface temperature – Thermal damping Water vapour diffusion resistance factor – Equilibrium moisture content (sorption moisture) – Hygroscopic moisture adsorption and discharge – Moisture transport – Preventing condensation – Construction moisture and drying – Side effects during drying Building material class – Fire resistance class – Classified timber building elements with earth infill

Airborne sound insulation – Sound insulation of timber joist floors

Content  7 

Appendix Sources and reference literature Publications of projects Index Picture credits About the author Glossary



296 301 304 308 309 310

Foreword First published in 1983 under the name “Leichtlehmbau – alter Baustoff – neue Technik” (Light Earth Building: New Techniques for an Old Building Material), this book arose in conjunction with a renewed interest in earth as an environmentally-friendly building material in the early 1980s and quickly became the first major reference book of its kind. The intention was to undertake an in-depth study of all the available literature and norms and to systematically examine ways in which walls, floors and roofs could be built using earth and straw. Aside from the lack of building codes, there was little knowledge of the building physics of earth as a building material. The key physical characteristics of earth, e.g. thermal performance, moisture resistance, sound insulation and its reaction to fire, had not been fully quantified. Initial comparative fire performance tests were undertaken to establish that the material has good fire-resistant properties, even with a high straw content. However, expensive thermal insulation testing methods were not possible, and a more pragmatic approach was taken by compiling information that already existed on the material’s thermal conductivity properties. Later sources corroborated these values and they were adopted, following a proposal by the author, in the “Lehmbau Regeln” (the German earth building codes) and in DIN 4108-4 (the German standard governing thermal protection and energy economy in buildings). While the homogenous, single-leaf light earth wall detailed in the original book has become the signature form of light earth construction, it is just one of a range of different possible applications. In the early 1990s we developed multi-leaf constructions with additional layers of insulation to improve energy economy and comfort levels as well as to meet the requirements of stricter regulations. These were included in the fifth edition of this book. In combination with natural, renewable or recycled thermal insulation materials such as cellulose fibres, it was possible to build sustainable and more energy-efficient constructions using timber and earth. With the introduction of additional layers of insulation, the light earth layer could be made thinner but heavier and more thermally retentive, enabling it to dry out more quickly on site. In 2013, the seventh edition of this book was published under a new title – “Bauen mit Leichtlehm, Handbuch für das Bauen mit Lehm und Holz” (Building with Light Earth, A Handbook for Building with Earth and Wood) – and with a new organisational structure that better reflects the division in earth building materials and building elements used in the “Lehmbau Regeln”. The book was expanded to include both traditional historical techniques as well as new methods of manually applying straw-clay and heavy light earth mixtures. These were based on the results of a research project in Limburg and numerous practical tests and investigations. Light earth is used solely in a non-loadbearing capacity as an infill material. In (timber) skeleton frame constructions it presents an alternative to the usual lightweight insulation materials, improving the physical characteristics of the building envelope and the room climate within. This edition of the book contains numerous practical examples of simplified wall constructions using earth and light earth that offer improved material characteristics, for example a very simple design-based means of moisture protection

Foreword  9 

that obviates the need for a vapour barrier and adhesive sealing tapes of questionable durability and longevity. Timber construction has always had the advantage of having a comparatively slender structure, freeing up more space for the floor plan. Today’s high-strength building materials are hard and in many cases stronger than they actually need to be. They are correspondingly hard to recycle, usually requiring shredding or crushing. Timber and earth constructions, by contrast, are easily adapted and converted to new uses, and the majority of its constituent building materials can be re-used or recycled. Houses made of timber and earth need not be expensive, and there are plenty of opportunities for clients and homeowners to personally contribute through self-building. The breadth of new projects – family homes, churches, children’s nurseries, schools, buildings for livestock, summerhouses, ateliers for artists and museums – shows both how versatile as well as how commonplace the use of earth as a building material has become. In industrialised nations, building with earth is no longer exotic but a modern, affordable and exceptionally sustainable way of building that also offers new aesthetic possibilities. Alongside the projects that illustrate how prefabricated earth building materials can be used in today’s construction processes, numerous self-built projects reveal how people have discovered the unique possibilities of this building material with their own hands. This, the eighth edition of this book, expands on techniques of building with light earth without formwork and details new developments in the earth building norms. The project section has been expanded to include projects from English-speaking countries. It was a pleasant surprise to discover that architects and builders around the world – inspired by earlier editions of this book – have been enthusiastically building with straw and earth and in the process have developed techniques and machinery of their own to prepare the material for construction. I would like to take this opportunity to once again thank all those who provided material for earlier German editions of this book: in particular Peter Breidenbach, Lydie Didier, Andreas Dilthey, Alexandre Douline, Lou Host-Jablonski, Hugo Houben, Franck Lahure, Alain Marcom, Aymone Nicolas, Sophie Popot, Teuvo Ranki, Johannes Riesterer, Ulrich Röhlen, Elias and Eva Rubin, Olivier Scherrer, Manfred Speidel, Juan Trabanino, Mikael Westermarck and Christof Ziegert. For this edition, I would especially like to thank the following people not only for contributing images and information but also for their suggestions and constructive criticism: Vasko Drogiski, James Henderson, Robert Laporte and Paula Baker-Laporte, Sandy Lidell Halliday, Chris Morgan, Florian Primbs, Michael Schauer and last but not least Ute Schauer. Franz Volhard September 2015

10 Light Earth Building

100 Introduction “Be not afraid of being called un-fashionable. Changes in the traditional way of building are only permitted if they are an improvement. Otherwise stay with what is traditional, for truth, even if it be hundreds of years old, has a stronger inner bond with us than the lie that walks by our side.” Adolf Loos, 1913

110

Earth as a building material

In central and northern Europe there is a long tradition of building with earth. European cultural and climatic conditions, together with the necessity of using locally available materials, gave rise to numerous different methods of using earth for building purposes: −− solid building constructions using earth for walls, floor and vaulted roofs −− hybrid building constructions employing earth in combination with wood and plant material for walls, ceilings and roof coverings −− stone masonry with earth mortar A particular characteristic of earth is that its composition varies from place to place. Earth is a mixture of clay, silt, sand and gravel or stones in different quantities and proportions. Not all earths are equally suitable for building purposes – the kinds of locally occurring deposits therefore determined the building methods used. Earth hardens exclusively through drying in air and does not chemically cure like gypsum or cement. Unlike other materials, if water is added, it will soften and can be refashioned into a new form. That means that it can be reused again and again, but also that it is sensitive to exposure to water. An important aspect of building with earth is therefore ensuring that the structure is protected against the potentially destructive effects of rain or water. A variety of techniques have developed in response to this: −− periodic repair and replacement of eroded external layers of the building envelope with new earth material, as seen for example in Africa −− protection of the earth material through water-resistant coatings such as renders, plasters or paints −− stabilisation of the earth material through additives −− prevention of moisture ingress by means of a weatherproof construction If left unprotected, earth buildings will return to what they once were. The earth from which they were made can be returned after use – whether demolished, collapsed or leftover building material – to the life cycle of nature without the need for extra processing and need not be disposed of as waste material. Excavations have revealed that a great flood reduced the ancient “antediluvian” Sumerian city of Ur to a three-­ metre-thick layer of earth.

Introduction  11 

120 Earth building methods

121

Solid earth construction

When earth is properly processed and of a suitable thickness, its compressive strength is sufficient to build multi-storey buildings of earth. In Yemen and North Africa there are examples of buildings that are eight to ten storeys high. In northern Europe, earth buildings were rarely taller than three to four storeys. To be useful as a loadbearing material, earth must have a raw density of greater than 1,700 kg/m³. The most important solid earth construction techniques are earth brick and earth block masonry, rammed earth and cob construction. Earth masonry is one of the oldest building methods. The cities of early advanced civilisations, such as those in Mesopotamia, were built with air-dried earth blocks or adobe bricks. The earth was either “patted” in a malleable consistency into a mould, applied by hand as a soft paste or rammed or pressed into formwork in a naturally-­ moist state. To stabilise the resulting mixture, chopped straw was added. Masonry walls were constructed with mortars made of lime or earth. Aside from these traditional methods, all of which can still be seen in many parts of the world, earth materials are also produced at an industrial scale, for example in adobe “farms” in New Mexico, USA. Compressed blocks can also be made in larger quantities on site using hand-operated or mechanised presses. In America, Brazil, Mexico and Algeria, compressed bricks and blocks are also factory-produced in automated production lines in a manner comparable to the industrial production of other building materials. Rammed earth is a more advanced earth building technique that likewise has a long history. As the walls are created directly on site, rammed earth is less time-consuming than the manufacture, drying and laying of bricks or blocks. Rammed earth is most common in regions where stony earth mixtures occur in appropriate compositions. Fig. 1 Street in the Lyonnais with rendered rammed earth buildings

12 Light Earth Building

121-03 Fig. 2 Earth block masonry

Fig. 3 Rammed earth

Traditional earth brick mould Traditioneller Formrahmen für Lehmsteine

Traditioneller Traditional rammed Stampfbau earth construction

Fig. 4  Traditional moulds for rammed earth and earth blocks

The naturally-moist, processed earth material, is rammed between two sets of shuttering boards or travelling formwork panels to create continuous, monolithic wall constructions. Traditional rammed earth techniques are still, indeed again, in use today in Latin America, Morocco, Afghanistan and China. In Europe, the USA and Australia, these have been developed into advanced techniques using large-format shuttering systems, mechanised processing and pneumatic rammers to reduce the degree of manual labour involved.

122

Frame construction

Earth is also used in frame construction as a non-loadbearing infill material for wall sections. A pre-erected roof construction ensures that vulnerable earth construction works are shielded from the weather. For this reason, this method is particularly wide­ spread in northern climatic zones with mild, wet summers. In central and northern Europe, as well as in Japan, timber-frame and traditional half-timbered constructions

Introduction  13 

are common. The transmission of loads from the roof and floors via posts or columns in the walls also improves structural stability in earthquake-prone regions (see project 24). This technique derives from the early tent, pile and skeleton frame structures with wattle walls daubed with earth [Soeder 1964]. Over the course of time, many different techniques have developed. In Europe, diverse means of applying earth to wattles, stakes or a lath of battens evolved, along with earth brick masonry. These techniques were once so commonplace and generally known that little is written about them in the literature. The fill material was mostly straw-clay, a mixture of earth and straw to lend the material stability. During the renovation of the oldest, 700-year-old, half-timbered building in Germany, the author had the opportunity to investigate the characteristics and qualities of these historical techniques, gaining valuable practical insight for the construction of new infill panels [Volhard 2010a].

Fig. 5 Wattle and daub panels, Marburg

14 Light Earth Building

130 Building with earth – a historical overview “ne caementorum quidem apud illos aut tegularum usus, materia ad omnia utuntur informi et citra speciem aut delectationem. quaedam loca diligentius inlinunt terra ita pura ac splendente, ut picturam ac lineamenta colorum imitetur.” Tacitus, Germania “They make no use of stone or brick, but employ wood for all purposes. Their buildings are mere rude masses, without ornament or attractiveness, although occasionally they are stained in part with a kind of clay which is so clear and bright that it resembles painting, or a coloured design.” Tacitus’ account tells us that the early Germans used wood and earth to build their dwellings. Stone and brick buildings were probably unknown at that time, not just in Germany but throughout all of northern Europe, and probably became gradually more widespread with the expansion of the Roman Empire. This can be seen in German terms such as Mauer (wall), Ziegel (brick), Mörtel (mortar) and Kalk (lime), which derive from the Late Latin words murus, tegula, mortarium and calx. In central Europe, skeleton frame constructions with wattle walling daubed with clay already existed in the Neolithic period. Archaeologists discovered settlements in Lower Austria that date back to the 5th or 6th century BC, and can be seen as reconstructions in the Museum of Prehistory in Asparn/Zaya. The history of earth building in Germany, Fig. 6 Rendered half-timbered

building, Tübingen

Introduction  15 

and in other neighbouring countries of the same general latitude, is essentially that of half-timbered construction. Solid earth constructions are rare, and generally restricted to isolated regions and certain historical phases, e.g. from the end of the 18th century to the middle of the 19th century, and in the times of need after the two World Wars. Half-timbered construction, on the other hand, remained the predominant building method for almost all kinds of buildings until the 19th century, and diverse regional house types and forms of construction developed over the centuries. Over time, a variety of different circumstances and new developments caused half-­ timbered construction to be displaced by stone and brick constructions. These include: −− The felling of forests caused a general shortage of wood from the 17th century onwards. Half-timbered construction consumed significant quantities of wood, and the intuitively-derived cross-sections of members were generally thicker than they need have been. −− Fires that occurred in more densely populated settlements frequently caused the destruction of entire sections of towns and cities. Brick and stone were less susceptible to fire. −− Brick and stone were better able to fulfil a need for greater durability and safety than perishable materials such as wood and earth. Because brick production also required wood to fire the ovens and stone buildings were expensive and often cold and wet, there was a brief period towards the end of the 18th Fig. 7 15th century half-timbered

building, Hasselt, Belgium, renova­ ted in 1996

16 Light Earth Building

century when the conditions for monolithic earth construction methods were good. In 1764, for example, the Prussian State decreed the use of earth lumps as an alternative to wood, which was then in short supply. In France, C. de Cadenet built a village in 1741 for farm labourers using a rammed earth technique (Charleval, Durance). In 1772, G. Goiffon published “Art du maçon piseur”, the first manual detailing the technique originating from the Romans and brought via the colonies to France. Shortly after, in 1790, the French architect F. Cointeraux published his famous “School of Rural Architecture” which included detailed instructions on Pisé construction. This book was translated into most European languages, the German edition being published in 1793 [Cointeraux 1793]. In 1797, D. Gilly also published his “Handbuch zur Land-Bau-Kunst” [Gilly 1818] in which he outlined this technique of building with earth. The uptake of the Pisé method in Germany, which was described as a means of building dwellings that were “extremely economical, healthy, durable, warm and absolutely fireproof” [Wimpf 1841] was, however, largely limited to localised pockets where particular individuals were especially active. In Weilburg, the factory owner Wilhelm Jakob Wimpf was responsible for the building of several rammed earth buildings, some of them several storeys high, most of which are still intact although not outwardly apparent as rammed earth buildings (fig. 8) [Erhard 1982]. In Austria too, rammed earth was not used widely and only a few isolated examples of historical buildings still remain [Kugler 2009].

Fig. 8 Rammed earth house, 1828/29, Bahnhofstrasse 11, Weilburg

Introduction  17 

In France, by contrast, a new culture of building with earth began to emerge in the 19th century in many parts of the country. Entire towns and villages, chateaus, residential buildings, schools, town halls, workshops, barns and farmsteads were built using rammed earth or earth bricks, many of which are still in good condition, for example in the rammed earth region of the Rhône-Alpes in the hinterland of Lyon and St. Etienne (fig. 1). The soil in this region is ideal for rammed earth: it is stony and gravelly but also cohesive, and can often be used without further processing for ramming between formwork. One of the reasons why rammed earth failed to become more widely adopted in Germany and elsewhere is that it did not build on a regionally pre-existing building tradition and many were therefore not receptive to the unfamiliar building method. In regions with less suitable soil, for example very silty soil, the preparation of a suitable mixture is laborious, in regions with very lean earth even impossible or dangerous. In more northerly climes, the weather conditions were less conducive to using rammed earth as a construction method. Earth brick masonry was more quickly constructed, especially under a roof, and more widespread as a result. Almost all the still existent earth buildings in Austria’s so-called “Ingenieurdörfer” (engineered villages) in northern Burgenland and the Weinviertel were built during this period out of earth brick, though many are at risk of being demolished. These houses with their traditional limewashed façades define the typical appearance of the local villages, and especially the Kellergassen, the cellar lanes (fig. 9). The loess soil typical of the region was mixed with chopped straw and originally formed into clumps that were then stacked on top of one another to form so-called “Wuzlmauern” (lump or ‘clat’ walls). Later, this mix was pressed into moulds and then dried to make earth bricks in Austrian format (29 × 14 × 6.5 cm) or blocks (approx. 30 × 15 × 15 cm) for “Quaderstockmauerwerk” (ashlar walls) [Kugler 2009, Maldoner/Schmid 2008, Bruckner 1996]. Fig. 9 Weinviertel, Lower Austria

18 Light Earth Building

The ultimate cause of the decline of earth building techniques, and likewise of half-­ timbered construction, from the mid 19th century onwards lies in the onset of industrial­ isation. New building tasks demanded new solutions: multi-storey buildings and wide spans were not achievable with earth building techniques, and its methods are not well-suited for façade decorations, cornices, projections and recesses. As new building techniques became available, earth building seemed backward, primitive and impoverished by comparison. New large-scale housing programmes could only be achieved with new industrialised building methods, and while the rest of the building sector became increasing industrialised, earth building remained a craft. With the tapping of coal resources, brickworks, cement factories and iron foundries arose producing new “durable” materials and even entire prefabricated sections of buildings. Earth building techniques were used at most for sealing, for screed floors and as ballast in suspended floors. “Earth building was ultimately brought to a standstill through a relentless one-sided campaign by building materials producers, most notably the fledgling brick industry. Banks would not finance earth constructions at the same conditions as other masonry buildings, and insurance companies started to be more discriminating. It has to be said, however, that many of the earth buildings of the time were a sorry sight with detached plaster resulting from improper building techniques.” [Hölscher et al. 1947] And indeed, the problem of achieving a good lime plaster bond on solid earth building constructions does seem to be a recurring topic in the literature of the day. The architect Hermann Muthesius likewise saw this as a key disadvantage of earth building (see below). But other methods, such as the traditional thin layer of hair-reinforced lime plasters applied to straw-clay infill panels, did not present such problems.

Fig. 10 Pisé building, France

Introduction  19 

With the end of the First World War, however, earth building experienced a revival in Germany. Materials that were dependent on coal for production were scarce, transport possibilities were limited and tradesmen few and far between. In the space of just a few years, more than 20,000 new earth buildings were built, mostly as self-built settlements in rural areas [Fauth 1946, 1948]. The “German Committee for the Advancement of Earth Building Methods” was founded and teaching and advice centres were established along with congresses and courses for training earth builders. Initial teething problems due to a lack of experience were soon overcome and the first scientific research was conducted into aspects such as fire safety, compressive strength and materials testing procedures at materials testing laboratories. A generally accepted state of the art of earth building soon emerged. However, despite state subsidisation, an official building code never followed. The phase of earth building was brief, lasting only a few years directly after the war until the building materials industry recovered and transport possibilities had “normalised”. Thereafter, earth building techniques were used only in individual cases. Towards the end of the Second World War, earth building represented a way of circumventing “the prohibition of all non-war-oriented building activities” [Hölscher et al. 1947]. Several exemplary settlements made of earth were built in Pomerania. In anticipation of the housing shortage towards the end of the war in 1944, a group of German earth building experts, among them Richard Niemeyer and Wilhelm Fauth, developed a draft ordinance as a formal basis for the reintroduction of earth building techniques – one did not want to be unprepared for the second time. This Earth Building Ordinance, the [Lehmbauordnung 1944], was published on 4 October 1944 in the Reichsgesetzblatt, the National Gazette. After the end of the war, earth building techniques were once again propagated as a method of building houses and workplaces with the few means available. Once again, a “German Council for Earth Building” was founded and numerous teaching and information centres established for training earth building labourers on building sites. This time, however, experts called for earth building to be included as part of the rationalisation and mechanisation of building after the war: “We must overcome the idea that earth building is a provisional building method. It must be given the same consideration as other construction methods with regard to mechanisation and industrialisation. The key to the success of earth building, as with the rest of the building sector, is systematic rationalisation.” [Pollack/Richter 1952] The scientific development of earth building was documented in the magazine “Naturbauweisen” (Natural Building Methods, fig. 14) and in numerous other publications. Earth building was put forward not just as a provisional method for times of emergency, but also as an economic and resource-efficient necessity. “The top priority for the leaders of an economy, especially one that has to overcome the devastations of wartime, has to be the prudent use of resources … The building of a house out of the soil of the earth on which it stands is an example of such prudence.” [Pollack/Richter 1952] Earth building activities in Germany were, however, most widespread in the then Soviet Occupation Zone following the Soviet Military Administration’s Order No. 209 for

20 Light Earth Building

Fig. 11 Social housing cooperative: residential building

for six families made of rammed earth, Dresden 1919/20 Fig. 12 Advertisement from 1921: Press for the rational manufacture of earth bricks and blocks

Fig. 13 Richard Niemeyer, Der Lehmbau und seine praktische Anwendung [Niemeyer 1946] (Earth building and its practical application)

Fig. 14 Naturbauweisen, Information sheet issued

by the Council for Earth Building at the GDR Chamber of Technology, 1948–50

Introduction  21 

Housing Provision, which decreed the building of 200,000 small farm homesteads, 40 % of which were to be built with natural and locally available materials. The building of 17,300 dwellings made of earth building materials that followed over a period of two years was calculated as having achieved cumulative cost savings amounting to 200 million bricks, 40,000 tonnes of lime, 110,000 tonnes of coal and 750,000 tonnes of transport capacity [Pollack/Richter 1952]. Earth building in East Germany continued until the end of the 1950s, but in West Germany was once again short-lived and restricted predominantly to the years immediately following the war. Although the Lehmbauordnung from 1944 was finally introduced as an official technical building norm in 1951 [DIN 18951 1951], and other preliminary norms followed until 1956, building with earth did not play a role in the Wirtschaftswunder years of growing prosperity in the 1950s. Why no effort was made to apply new technological possibilities to earth building remains a mystery, particularly given the fact that during the same period in the USA – in an age not characterised by austerity –, earth was being rediscovered as a building material that could be economically produced with the help of new industrialised processing and fabrication methods [Vick 1949]. In Germany, there were few such efforts, most notably the “Tonadur” bricks and panels produced by a Bavarian brickwork producer for the infill of walls, floors and roof inclines [Tonadur 1949]. In all the old books on earth building, however, little space is devoted to traditional methods and building materials, for example straw-clay and light earth, despite the fact that skeleton frame construction had remained one of the most common construction methods in Northern Europe over centuries. One possible reason for this may have been the shortage of wood in the times of crisis in which earth building was most widely used: during and after the wars [Speidel 1983]. Various high profile architects have also turned to earth as a means of building, especially during the times of crisis. In Austria, shortly after the First World War, Adolf Loos employed earth building materials for the Heubergsiedlung in Vienna. In some of the first construction lectures to take place after 1945, Egon Eiermann instructed his students in Karlsruhe in earth building methods (fig. 19), and Otto Bartning erected a settlement built using earth materials for the Protestant church’s Diakonisches Werk in Neckarsteinach near Heidelberg in 1946 (figs. 17 and 18). However, all these initiatives still had the character of a provisional method during times of crisis [Speidel 1983]. The architect Hermann Muthesius recommended earth building for small rural buildings, but voiced reservations about the extended construction times required for rammed earth walls and problems with plaster adhesion. In France, Le Corbusier was, unfortunately, not able to realise his Murondins project in 1941. French architects and engineers were most active in earth building in the former colonies of Algeria, Morocco and Senegal, developing a new form of modern architecture using a cement-stabilised rammed earth technique that they called “béton de terre” (M. Luyckx 1944, J. Dreyfus 1954). In Morocco, the engineer A. Masson oversaw the construction of 2,700 houses from 1962 to 1967, which were built of stabilised earth blocks [Nicolas 2011].

22 Light Earth Building

Fig. 15 DIN 18951 1951: Earth Buildings, Regulations for Construction (withdrawn without replacement in 1971)

Introduction  23 

Fig. 16 House in Bad Dreikirchen, South Tyrol. A building in the local vernacular: stone walls laid in earth

mortar (architect: Lois Welzenbacher 1923)

“… but, I hear you say, this cumbersome process of ramming earth is not rational, not modern. Lightweight, prefabricated houses are the future of building. That as may be. But, if the research and development of prefabricated houses needs five years in America, it will certainly be 15 years or more before we are that far here in Germany. In our use of earth, we are working in the present, where we have no coal and no means of transport. Once there is enough coal, we will start to fire bricks again …” Otto Bartning, 1948 In 1971, at a time in which faith in progress was at its zenith, the German earth building norms were withdrawn without replacement. Rediscovery A few years later, however, interest in earth building was rekindled in the context of the worsening energy crisis in 1973 as part of a growing awareness of the need for less energy dependent, more environmentally friendly and non-toxic building materials. But, although building with earth had excellent credentials in all these respects, it was all but impossible to build with earth. Craftsmen with the appropriate skills were no longer available and there were (at that time) no commercially-available earth building materials. Following a few first pioneering attempts in the early 1980s, the use of light

24 Light Earth Building

Fig. 17 Rammed earth construction,

Neckarsteinach 1946

Fig. 18 Self-build settlement in Neckarsteinach, 1946 (directed by Otto Bartning)

Fig. 19 Settlement for post-war resettled citizens in Hettingen, 1946–47, earth block masonry internal walls (architect: Egon Eiermann)

Introduction  25 

earth in timber frame constructions and the repair of half-timbered buildings gradually became more widespread. These developments were spurred on in part by the publication of the first edition of this book in 1983, which went on to become a standard reference book in the field. A further focal area was the rediscovery of earth as a building material for the preservation of historical monuments, especially half-timbered buildings. It had become clear that the new building materials and sealants used during the 1960s were often the cause of damages to old structures, and that there was a need for more sustainable and authentic techniques. In these early years, due to a lack of suitably qualified craftsmen, there was no alternative but to undertake much of the building work oneself using building materials made directly on site. But by the 1990s, professional interest in earth construction was rising. Building contractors began to offer earth building services, and some firms even began to specialise exclusively in earth building. The increase in demand led to corresponding developments in the production of prefabricated earth building products for diverse uses, including earth bricks, mortars, plasters, light earth and straw-clay for on-site use as well as building boards in a variety of formats. One company was particularly responsible for the rapid growth of this market sector: Lehmbau Breidenbach, now more widely known as Claytec. The growing circle of people involved in earth building led to the establishment in 1992 of a non-profit-oriented earth building association, the “Dachverband Lehm” (DVL), as a forum for the exchange of information and ideas between manufacturers, the trade, architects, academics and clients. Since its founding, the association has devoted significant effort to elaborating a consensus of the state of the art of earth building in the form of a building code. In 1998, the publicly-funded development process, in which the author played a significant role, Fig. 20 New light earth building, 1986

26 Light Earth Building

Fig. 21 The first new building to be built using light earth in 1983 (see project 2)

Fig. 22  Renovation and conver­ sion of a house in Alsfeld (Markt 2) from 1350 with new panel infill made of straw light earth (con­ struction: Talis company, 1989)

Introduction  27 

Fig. 23 Product range, Claytec 1992 (Claytec®)

Fig. 24 Development of prefabricated products (Claytec®)

Fig. 25 Earth panel production 1996 (Claytec®)

28 Light Earth Building

culminated in the publishing of the “Lehmbau Regeln” by the DVL. The code has since been incorporated into the technical building regulations of nearly all the Federal States of Germany [Lehmbau Regeln 1998 and 2009]. Since 2010, a work group has elaborated detailed norms for the most important industrially-produced earth building products, an essential step for the production, labelling, testing and application of modern industrial building materials. The DVL also addressed the establishment of skills and knowledge in earth building – previously communicated in local initiatives, seminars and course, and a few isolated universities and higher education institutions – through the development of a formalised theoretical and practical training course, running over a period of several weeks. The “Fachkraft Lehmbau” course trains craftsmen and women in the specialisation of earth building and is overseen by a regional chamber of trades. Successful completion enables participants to enrol in the Register of Craftsmen, giving them the same status as other building trades (Register A, Bricklayers and Masons, Specialisation: Earth Building) [Dachverband Lehm]. In France, the CRAterre group (International center for Earthen Architecture) has developed since the 1980s and is now recognised around the world as a leading centre for earth building. The group formed at the École d’Architecture de Grenoble, partly as a response to the impressive tradition of Pisé architecture in the region. In 1979, the book “Construire en Terre” [CRAterre 1979] was published as a first systematic attempt to document earth building around the world. In 1989, a comprehensive handbook followed entitled “Traité de construction en terre” [CRAterre 1989]. In 1984, CRAterre began offering a two-year course (CEAA Terre) together with the École d’Architecture de Grenoble that has since become the DSA Terre post-master diploma. Comprising a combination of theoretical tutoring and practical application, it remains the only course of its kind to date. The group also oversaw the construction of construction projects, especially abroad. The largest and most successful of these is an earth building project that began in 1981 on the island of Mayotte, comprising 20,000 dwellings made of hand-pressed, locally-made compressed blocks (fig. 26). In 1981, Jean Dethier and CRAterre organised a major exhibition entitled “Architectures de terre” at the Centre Georges Pompidou in Paris, which went on to travel to other museums, including the Deutsches Architekturmuseum in Frankfurt. The catalogue was translated into several languages [Dethier 1981]. The exhibition also gave rise in part to a spectacular follow-on project: “Le Domaine de la Terre” in Villefontaine near Lyon. A total of 65 social housing units designed by different architects were built as a means of demonstrating the economic potential of rammed earth, compressed earth blocks and light earth in contemporary conditions (see project 3 and fig. 28). Parallel to these developments, initiatives have sprung up all over France using earth for the renovation and repair of historical earth buildings. Earth building has become more professional and earth building products are available on the market. A network of contractors gradually emerged, culminating in the foundation of AsTerre, the French network of professional earth building contractors, in 2006. Here too, a primary task will be the development of building codes for earth construction.

Introduction  29 

Fig. 26 Houses on the island of Mayotte 1982 (CRAterre)

Fig. 27 Terstaram® press, ­Mayotte 1982

Fig. 28 The Domaine de la terre settlement at Isle d’Abeau

30 Light Earth Building

In other European countries, as well as in the USA, Australia and New Zealand, active earth building groups have been developing since the 1980s. Various national associations have been founded and university institutes around the world are undertaking research, development and teaching in earth building. Norms and standards are being developed in several countries – or being adopted and adapted from building codes from other countries (see chapter 732).

140 Building with earth today? The energy crisis in 1973 made it painfully clear how dependent modern industrial nations are on a steady flow of oil for their continued prosperity and living standards. The limits of growth and of environmental exploitation were noted: “The crisis […] will become worse and end in disaster, until or unless we develop a new lifestyle which is compatible with the real needs of human nature, with the health of living nature around us, and with the resource endowment of the world. “Now, this is indeed a tall order, not because a new life-style to meet these critical requirements and facts is impossible to conceive, but because the present consumer society is like a drug addict who, no matter how miserable he may feel, finds it extremely difficult to get off the hook. The problem children of the world – from this point of view and in spite of many other considerations that could be adduced – are the rich societies and not the poor. “… The system of production by the masses mobilises the priceless resources which are possessed by all human beings, their clever brains and skilful hands, and supports them with first-class tools. The technology of mass production is inherently violent, ecologically damaging, self-defeating in terms of non-renewable resources, and stultifying for the human person. The technology of production by the masses, making use of the best of modern knowledge and experience, is conducive to decentralisation, compatible with the laws of ecology, gentle in its use of scarce resources, and designed to serve the human person instead of making him the servant of machines. I have named it intermediate technology to signify that it is vastly superior to the primitive technology of bygone ages but at the same time much simpler, cheaper, and freer than the super-technology of the rich. One can also call it self-help technology, or democratic or people’s technology – a technology to which everybody can gain admittance and which is not reserved to those already rich and powerful.” E.F. Schumacher: Small is Beautiful: Economics as if People Mattered, 1973 “The catastrophe is not brought on by nature, but by people alone. And one way or the other, the catastrophe can only be held off if people either return to the laws of entropy, or find ways of circumventing the limits of the sun without causing harm.” G. Moewes: Weder Hütten noch Paläste [Moewes 1995]

Introduction  31 

In this respect, building with earth, wood and plant fibres is one of the few techniques that needs no more than the sun’s energy. Earth dries in air and can be re-plasticised and reshaped through the addition of water, and wood and plant fibres have a net zero carbon footprint. The building technology is simple and available to everyone, and uses raw materials that can be found almost everywhere in relevant quantities without requiring energy-intensive pre-processing. In addition, despite already being well practised, it can be developed further. Today, many building materials are already termed sustainable if it is technically possible to recycle them, irrespective of the fact that shredding and melting down are energy-intensive processes that are also dependent on the continued availability of fossil fuels. Earth and wood, by contrast, can be reused again and again with minimal energy requirement and when no longer needed can be returned to nature without harming people or nature. In addition to the aforementioned aspects, there are plenty of other reasons for employing earth as a building material. When faced with the high cost of building, people sometimes elect to undertake some of the building works themselves. Earth building offers many ways in which people can bring their own ideas and skills to bear, either in the making of earth building materials on site, or in using ready-made earth building materials. More and more people are interested in the building material itself, as are manufacturers and contractors. The latter in particular, due to their qualifications and better equipment, are able to apply the technique at a larger, more professional scale than is possible for the self-builder, and are in a position to develop techniques further. Earth is, of course, not suitable for every kind of building task. It’s low compressive strength means that loadbearing earth constructions are typically limited to one or two storeys (taking safety margins into account). A further disadvantage is that the necessary drying times for wet earth building materials restricts the possible construction period to the drier months of the year. But for many building tasks – such as low-rise housing (also in urban areas), single and multi-family homes, the renovation of existing buildings (especially half-timbered buildings), rural buildings (both dwellings and agricultural buildings), and public buildings such as schools and children’s nurseries – earth does represent a viable alternative or supplement to other building materials, particularly in association with a loadbearing timber frame. Building with earth is now a proven building technology. One must, of course, observe the material-specific technical particularities, but with adequate knowledge, experience as well as care in the planning and undertaking of building works, there is no reason not to exploit the advantages of this obvious and readily available material.

32 Light Earth Building

150 What possibilities can earth building techniques offer today? The traditional adage about earth construction – “warm in winter, cool in summer” – must be seen in the context of the technological standards of the time. Modern day requirements expect more constant environmental conditions. At the same time, fossil fuels need to be used much more sparingly. This has resulted in regulations that prescribe minimum levels of insulation that are not achievable with a normal wall – whether a thick solid earth wall or a conventional brick wall. Additional insulation is required. Loadbearing earth constructions made of rammed earth, earth block masonry or cob obviate the need for expensive timber frame constructions but the thick walls plus insulation consume valuable floor space. Only once the walls have been finished can the roof be built and when it rains, work has to stop and the walls need to be covered. That notwithstanding, the adoption of the building code in Germany [Lehmbau Regeln 1999] has at least made it possible to obtain planning permission for loadbearing earth walls up to a height of two storeys. For non-loadbearing constructions, such as timber frame construction, earth building materials can be used in many different ways. In essence, modern timber and earth constructions are a technological advancement of the historical tradition of panel infill in half-timbered constructions. In addition to earth bricks and blocks, and straw-clay and other fibre-based mixtures – typically in combination with additional layers of insulation –, light earth building materials offer several physical, technical and practical advantages.

160 Building with timber and earth

161

Straw-clay and fibre-clay mixtures

The term “straw-clay” or “fibre-clay” denotes earth mixtures with a dry bulk density of between 1,200 and 1,700 kg/m³. The earth is mixed with straw or other fibres into a soft malleable form [Lehmbau Regeln 2009]. Typical application areas include wall and ceiling panel infill and thick layers of plaster. Earth mixtures can also be prepared using all manner of fibres, the majority of which are finer than straw resulting in a consistency that – unlike straw-clay – is suitable for making products such as earth bricks, mortars for thin layers of plasters or spray-applied mortars. These mixtures are known under the generic term “fibre-clay”. The earth mixture is reinforced with shredded or chopped straw stems, which helps to reduce plaster cracking and erosion, and improves its insulating properties. The most common method of application is described in detail later and is a precursor to working with light earth (see chapter 420). In the traditional wattle and daub method, the panels formed by the vertical and horizontal members of the half-timbered structure are filled with a wattle made of hardwood stakes woven with supple willow branches onto which a straw-clay or chopped straw-clay mix is applied, or daubed. In some areas (Normandy, for example), a lath of spaced battens serves as a backing onto which the straw-clay is hooked,

Introduction  33 

Fig. 29 Fibre-clay plaster mortar with chopped straw, Fig. 30 Straw-clay, made with bale straw prepared as a naturally-moist mix

Fig. 31 Section through moulded earth brick made of fibre-clay

Fig. 32 Straw-clay, dry ready-mix formulation

straddling it in a saddle-like manner, before being smoothed over. In the case of stakes, horizontal timber stakes are wedged into notches in the vertical studs. Once the timber frame, including the floors, has been fitted with stakes, the stakes are either wrapped in place with a straw-clay mix, or taken out panel for panel, and then reinserted in alternating layers of straw-clay and stake. The surface is then smoothed over or plastered with a layer of finer straw-clay. Vertical stakes wedged between horizontal

34 Light Earth Building

161-04

a) wattle a) Flechtwerk

b) continuous wattleFlechtwerk b) durchgehendes

c) horizontal stakes c) waagrechte Stakung

d) vertical stakes d) senkrechte Stakung

e) enges Fachwerk, Stakung e) tightly-spaced timber posts with stakes

f) weites Fachwerk, Lattung f) widely-spaced timber posts with laths

Fig. 33 Panel infill with straw-clay

timber beams but without the additional willow wattle is also common in some regions (South Germany, for example). Here enough straw is mixed into the earth mixture to enable the mass to be worked into the spaces between the stakes. Earth reels are a further method in which the stakes are first wrapped with a ‘reel’ of straw-clay and then wedged into the prepared notches in the timber-frame panel while still moist. The reels are pressed up against each other and then coated with a layer of fine straw-clay to create a smooth surface (see chapter 432).

Introduction  35 

162

Light earth

Light earth is an earth building material that has an insulating effect that is especially suited to temperate climates. Light earth, like straw-clay is a mixture of earth and straw or other lightweight fill materials, which form the primary constituent of the mass. The earth serves predominantly as the binding matrix for the aggregate. Light earth is a panel infill material for use within a loadbearing timber framework, which can, however, be more slender than traditional half-timbered constructions, and therefore more economical in its use of wood. This has the advantage that light earth building work can take place under a roof that already exists and is therefore unaffected by the weather.

Fig. 34 Light earth construction [Fauth 1946, 1948]

1. Straw or other fibres are chopped to a length of 10 to 15 cm. 2. Liquid earth is poured over each layer of fibres and 3. mixed well with a pitchfork. 4. The mixture is inserted between shuttering. 5. Compaction of the mass and 6. insertion of horizontal stakes to stiffen the wall construction. Fig. 35 Tools for light earth construction

[Fauth 1948]

36 Light Earth Building

Fig. 36 Light earth

The technique arose in Germany some time after 1920 out of the traditional strawclay approach. At that time, they were already aware of the better physical and thermal characteristics of the lightweight, aerated building material. This method was initially called straw-clay studwork, which later became light earth building [Fauth 1946] [Niemeyer 1946] [Pollack/Richter 1952]. The term “light earth” is first mentioned in the Lehmbauordnung from 1944. It was described as an earth mass mixed with a lightweight aggregate with a bulk density of less than 1,200 kg/m³. Medium-grade light earth is 600 to 800 kg/m³ and very lightweight light earth mixtures of around 300 kg/m³ are possible when using a very clay-rich earth. Light earth mixtures made with other fill materials are named after the respective material, for example “woodchip light earth” or “mineral light earth”. In contrast to the other earth building materials, the earth material is mixed with straw or other fill materials in a fluid state. The mixed light earth mass is then filled into sliding formwork and compressed directly in the wall or else formed into bricks, panels or blocks which, when dry, can then be laid like bricks in mortar. The insertion and compression of the malleable mass, which can pressed into every last corner, is simple and requires less time and labour in comparison to rammed earth, earth block or cob wall constructions. The necessary drying time does, however, require that building work begins in the early summer months if the building is to plastered in autumn. Where necessary, artificial forced drying can be used. Dry bricks and panels, on the other hand, can be laid at any time of the year provided that the construction is not exposed to frost. A combination of both methods can be advantageous, making the construction time largely independent of the time of year. Due to its technical and physical properties, light earth has proven to be an increasingly contemporary building material – especially in comparison to the common panel materials and insulation infill used in modern timber frame construction:

Introduction  37 

a) Geschalte Wände a) Geschalte wall Wände a) Shuttered

b) Mauerwerk b) Mauerwerk b) Brick masonry

c) Wall infillininverlorener lost formwork c) Füllung Schalung c) Füllung in verlorener Schalung

d) Masonry in timber frame d) Fachwerkausmauerung d) Fachwerkausmauerung

Fig. 37 Panel infill with light earth

−− Light earth can be used as an infill material for all building elements above the foundation and stem walls, and is applied in largely the same way using the same basic material. This includes external and internal walls, floors and roof insulation. −− Light earth building elements can be plastered, clad or additionally insulated without additional intermediary layers. Its rough, open-pore surface provides an excellent mechanical key for all kinds of plasters. −− The infill material adapts to fit its container and forms a continuous monolithic mass. There is no offcut or waste material to dispose of. −− When plastered, the panel infill is windproof, obviating the need for vapour barriers, which are often the cause of problems in timber construction. Electrical installations do not present a problem. −− Light earth has a balanced mix of thermal insulation, thermal retention and sound insulation properties and provides an adequate level of fire resistance. This property can be adjusted by altering the mixing proportions of earth and aggregates. −− Thermally insulating light earth (300 to 800 kg/m³) makes it possible to create a comfortable interior with good room surface temperatures even with relatively thin wall thicknesses. As a consequence, the room air temperature can be reduced, in turn saving on heating costs. The relatively high surface weight at good insulation

38 Light Earth Building

Fig. 38 Plank stud construction with light earth wall infill in a house in Victoria, Australia, 2011 (see project 26)

levels evens out fluctuations in the outdoor temperature, ensuring that the interior is also comfortable in summer. −− While single-skin external walls made with light earth only rarely fulfil today’s extreme thermal insulation requirements, very low U-values can still be achieved with additional insulation but without requiring as much mass as an insulated masonry building. The frame construction impacts less on the available floor area. −− Where good thermal retention and noise insulation properties are required – desirable, for example, for internal walls –, the proportion of earth in the mixture can be increased, increasing its bulk density. −− Its fire-resistant properties are a product of the complete coating of the combustible plant fibres in non-combustible earth material. Plastered light earth infill panels have fire retardant properties. −− Timber and straw that is properly coated in the earth mix is protected against rot. −− Light earth can absorb and release moisture. Its good vapour diffusion and capillary conduction properties at low levels of equilibrium moisture mean that walls stay dry and maintain their thermal insulation capacity. −− Earth, straw and wood are all natural building materials that are non-toxic both during and after installation.

Introduction  39 

−− The material costs are low. Compared with heavy, loadbearing earth building techniques, less than half as much earth is required, reducing the amount of material that may need to be transported to the building site. −− The working method is easy to learn and easy to undertake oneself. Only a few simple tools are required. Self-build work is restricted to the panel infill and therefore cannot endanger the structural stability of the building. Errors are generally easy to correct. −− Light earth is now a tried and tested material and technique. With the use of building machinery, building with light earth has the potential to compete with other building methods.

Fig. 39 Earth is an ideal material for self-building

Fig. 40 The latest light earth project: A small weekend house in the tropical rainforest. Queensland, Australia 2015

40 Light Earth Building

200 Building materials for light earth 210 Soil and earth Earth is excavated soil and comprises clay minerals and other constituents ranging from fine sand to stony particles. Soils that are cohesive (i.e. have a strong binding capacity) are termed rich, or clayey, those with low cohesion, lean or sandy. Depending on the predominant grain fraction (the most common particle size) in the soil texture, soils are known as ‘stony’, ‘gravelly’, ‘sandy’, ‘silty’ and so on. The clay serves as a natural binder for these ‘aggregates’ and consists of crystalline wafer-like sheets, or lamellae, of less than 1/2,000 mm thick. These lamellae lie, like a stack of cards, tightly packed on top of one another. When clay comes in contact with water, very thin films of water form between the internal surfaces of the lamellae, allowing them to slide over one another. Wet earth or clay therefore has a characteristic slippery feel, while less wet earth feels moist but malleable. As the water evaporates, molecular attraction across the surfaces of the lamellae causes them to bond together. It is this that lends clay its cohesive qualities and explains why it hardens into a strong mass when dry. Sand, by comparison, has round grains which only touch each other at minute points on their surfaces.

Fig. 41 Earth pit

Building materials for light earth  41 

210-02 CAD

größte Schluffpartikel Largest silt particle 60microns Mikron == 0,06 mm 60 0.06 mm

SmallestSchluffpartikel silt particle kleinste 22 Mikron mm microns==0,002 0.002 mm

kleinste SmallestTonpartikel clay particle 1 Mikron ==0.001 mm 0,001 mm 1 micron

Sandkorn Grain of sand 1 mm 1 mm

Fig. 42 Grain sizes in comparison (after Piltingsrud)

210-03

liquid a) semi-liquid, breiig, flüssig

b) plastisch b) malleable

c) solid fest Fig. 43 Consistency of clay particles depending on water content [Hamer 1975]

The processing of earth prior to construction serves to distribute the water added to or already within the material as evenly as possible so that the lamellae of the clay molecules are better aligned and form a stronger bond. Earth prepared in a wet or fluid state will therefore be of greater strength than earth used in its naturally-moist state. As the mixing water evaporates into the surrounding air, the volume of the earth mass decreases. The more water added and the higher the proportion of clay in the mix, the greater the degree of shrinkage. A clay-rich earth has a larger internal surface area and can absorb more water than a lean mass of the same consistency. To reduce the degree of shrinkage to a tolerable level to prevent crack formation, earth is blended with aggregates to make the mass leaner for building purposes. The quantity of aggregate required depends on the cohesion of the earth used. Light earth materials have a high proportion of lightweight aggregates or fibres that serve to both lean and stabilise the mixture.

42 Light Earth Building

After drying, a degree of water – the so-called equilibrium moisture content – remains in the pores of the clay particles. As the name suggests, this varies depending on the ambient humidity of the surrounding air, and only evaporates under prolonged drying at 105°C. Water that is chemically bound to the surfaces of the clay crystalline minerals can only be driven off by firing clay at temperatures upwards of 600°C. At temperatures in excess of 900°C, earths and clays change chemically (like ceramics and fired bricks), becoming water-impervious and losing the ability to be softened and reformed through the addition of water.

211

Soil formation and deposition

Residual mountain soils are a weathering product of primary or sedimentary rock that lie at their place of origin. Soils that originate from sandstone or shale have round grains and are often hard to differentiate from transported alluvial earths (see below). Soils that originate from granite, gneis or syenite comprise a rubble of angular grains that grow increasingly large with depth. As the name suggests, such soils are found in hilly and mountainous regions, but also in the lowlands of Europe. Alluvial soils – soils in rivers, floodplains and mud – are a mix of older soils that have been transported and deposited by water, coming to rest in calmer waters. Earths that are dark in colour with a strong humus content are not suitable for building purposes. White-coloured marl is a chalky, lime-rich mineral produced by the motion of glaciers during the ice age. In Germany, this glacial till was pushed as far as the Mittelgebirge highlands of Central Germany and can be used if the lime content is not too high. Brown loess soils are a weathering product of loess out of which the lime content has leached. Loess is a loosely compacted yellow-coloured, lime- and clay-rich fine sand which was transported to its place of deposition by the storms of the ice age. In Germany, this is most commonly found on the northern fringes of the Mittelgebirge. Loess soils have a very fine grain texture and often a low clay fraction. The origin of a soil to be used for building purposes is less relevant than its respective properties, in particular its degree of cohesion and the distribution of particle sizes within the soil texture.

212 Cohesion Earths for light earth building need to be suitably adhesive (i.e. rich to semi-rich) in order to effectively bind and coat the lightweight aggregate material in liquid form but dry enough to harden properly. According to the “Lehmbau Regeln”, this is the case with a cohesion (binding force) of 100–120 g/cm² (semi-rich). The richer the earth, the less material required and the more it can be diluted. The bulk density of the resulting mass is then lower. According to Niemeyer, the cohesion of earths for light earth should be at least 160 g/cm² (semi-rich). Richer clays do not, however, dissolve so readily into a fluid state and in practice semi-rich and leaner earths are often used. This is possible when the clay slip or slurry is not too thin and can effectively coat the fibres and aggregates. Very lean earths (50–70 g/cm²) are only suitable for building when of a thick or pasty

Building materials for light earth  43 

consistency and the resulting light earth material is correspondingly heavier. Such earths are suitable for straw-clay and other fibre-based mixtures.

213

Soil texture

The particle size distribution (psd) of the earth plays a lesser role in light earth building than in other earth building techniques as the mass is sufficiently stabilised by the fibres and aggregates. Nevertheless, coarse sand and stony particles reduce the insulating properties of the mixture because they displace trapped air in the mixture, and make the material harder to work, depending on the preparation and mixing method employed. One should therefore use earths that have as little sand and stony particles as possible, or at least pick out, sieve or wash out the larger particles. For straw-clay and other fibrous earth mixtures, the sand fraction is irrelevant and only presents a problem when working the material by hand. To precisely determine the particle size distribution, it is possible to sieve the resulting material after washing out the fine particles 80–110 > 110–200 > 200–280 > 280–360 > 360

Fig. 46 Classification of earth for building according to cohesion [Lehmbau Regeln 2009]

Building materials for light earth  45 

The binding strength test according to DIN V 18952 Sheet 2 provides an immediate indication of the technical suitability of a soil for building purposes for various applications. The leaning effect of any lime content present is also assessed in this test. Brief description: The resistance to rupture that a soil or earth sample in a plastic state exhibits in the tensile test is a product of the sample’s material cohesion and is described by its binding strength. In order to determine the binding strength, the earth is carefully prepared to a defined test consistency. A test body is then formed and tested to the point of rupture in the test apparatus. The resulting binding strength is given in g/cm² or N/mm². Earth with a binding strength of less than 50 g/cm² cannot be further differentiated through the binding strength test. In general, such earth is not suitable for building purposes. The potential suitability of such earth for other specific purposes must be tested using other appropriate means. Binding strength test, method of testing Preparation of earth sample Each test requires around ¾ of a litre of earth in a dry or no more than ground-moist state. All grain sizes in the mineral framework above 2 mm shall be removed from the sample by sorting or sieving the dried, pulverised earth. The earth is beaten flat on a metal plate in a near-ground-moist state using a hammer with a head surface area of 2.5 × 2.5 cm one strike at a time adding a small amount of water, until a contiguous pancake is formed. The pancake is then removed from the plate using a knife and cut into strips. These strips are then placed on edge next to each other and hammered flat. This process is repeated until no irregularities in the structure of the material can be seen on the underside of the pancake. If the earth sample was too dry at the beginning of preparation, it must be left to rest under a damp cloth for 6 hours after hammering, or 12 hours in the case of clay-rich earth samples. This allows the moisture to spread evenly throughout the entire mass of earth. Producing the test consistency 200 g of the prepared earth is compacted on the plate by impacting it onto the plate repeatedly. Directly thereafter, a ball is formed by hand. The sample should not be formed for a prolonged period as it loses moisture through the surface of the ball, resulting in an uneven consistency of the sample. The ball is then dropped onto a flat, inelastic plate from a height of 2 m (measured from the centre of the ball). When the diameter of the ball spread on impact is 50 mm, the earth sample has the proper test consistency. If the spread is not circular, the difference between the largest and smallest diameter may not exceed 2 mm. Production of the test body Earth at the test consistency is compacted in the mould for the test body (see fig. 1b) in 3 layers using a tamper (see fig. 2) until no further compaction is possible. The surface of the test body is trimmed flat on both sides using a straight-edged knife. The mould separates from the test body when dropped from a height of 10 cm onto a hard surface. At least 3 test bodies should be made. Tensile test The test body is mounted into the test apparatus shown in figure 3 immediately after its production and subjected to a gradually increasing load through the continued addition of dry sand (of 1 mm grain size) using the apparatus shown in figure 4 (or some other suitable test apparatus) until the test body ruptures. The load should be added at an even rate not exceeding 750 g/minute. The binding strength of the soil or earth sample is the average result of three tensile tests. To be valid, these tests should not deviate from one another by 10 %. The results are expressed in g/cm² or N/mm². The calculated cross-section of the test body is 5 cm². The weight of the lower half of the test body is not taken into account. Fig. 47 Cohesion test according to the Lehmbau Regeln [Lehmbau Regeln 2009]

46 Light Earth Building

215-02

78 26

39

52

22.5

22.3

10

Bild 1b Form für test den specimen Probekörper 1b) Mould for the

Bild 1a Gestaltofdes 1a) Dimensions theProbekörpers test specimen

39

200

Ø 70

20

22

35

zu Bild 3from image 3 Bracket

Bild 2 Stampfer 2) Tamper

Bild 1c Unterlegplatte für die nach Bild 1b 1c) Base plate for the mould in Form 1b

Inhalt Contents, 2,5 2.5 Liter litres

Slider to control Schieber flow rate

Rinne Channel

Bild 3 Zugfestigkeitsprüfer 3) Tensile strength test apparatus

Bild 4 Einlaufgerät 4) Controlled filling apparatus

Fig. 48 Test apparatus for the cohesion test [Lehmbau Regeln]

Building materials for light earth  47 

Fig. 49 Cast bronze mould used previously to test concrete

Fig. 50 and 51 Cohesion test, preparing the earth to a defined test

consistency

48 Light Earth Building

Fig. 52 Preparing the earth material with a pasta

Fig. 53 Checking the material stiffness, spread =

making machine

50 mm

Fig. 55 Testing apparatus with steel brackets Fig. 54 Figure of eight mould

connected with nylon threads and gradual weight gain using a bottle with nozzle

Building materials for light earth  49 

The precise procedure of the test is shown in figures 46 to 48, with additional notes below. The figure-8-shaped test specimen derives from early methods of testing concrete (fig. 49). A wooden mould (fig. 54) is fine for a few applications, but a steel mould is more durable. The clips should be freely suspended to avoid the impact of any asymmetrical loads. They can be attached to each other with thin nylon threads so that the assembly does not clatter to the ground when the earth specimen breaks. Instead of using sand, the weight can be increased just as easily using water. A lightweight metal can equipped with a wire handle is just fine. The prescribed increase in load can be achieved using a suitably gauged funnel inserted into the lid. The can need only be suspended a few mm over the surface of the table. The binding force test can be simplified using modern laboratory equipment. 0

50

0

20

Cohesion [g/cm2] 100 150

200

250

80

100

Earth 1 Earth 2 Earth 3

Cohesion [g/cm2]

40 60 Grain particle size [m%] < 0.06 mm

0.25–1.0 mm

0.06–0.25 mm

1.0 –2.0 mm

Fig. 56 Example of the classification of earth for building according to its key characteristics: cohesion and soil texture

Geotechnical classification While soil testing methods are now commonly used all over the world to test the suitability of earth for building purposes, their suitability in practice is increasingly being called into question. CRAterre, for example, highlights the laborious process of sedimentation testing (see [DIN 18123 2011]) as a means of determining the particle size distribution within the clay fraction: “Why do we need to know the precise quantities and distribution of clay particles down to two decimal commas, when what we are really interested in is their quality?” [CRAterre 1986, p. 13]. The percentage proportion of the clay fraction, i.e. the quantity of particles less than 0.002 mm in size, is an unreliable indication of the cohesion because clay minerals can have quite different plastic characteristics depending on their respective form. The sedimentation procedure can be used to separate grain particles of different sizes but not form. The calculation of the grain diameter based on the sedimentation velocity assumes that the particle is spherical. But clay crystals are anything but spherical, as they would not otherwise exhibit such cohesive properties [Kézdi 1969, p. 29]. For this reason, laser diffraction is often used today in place of sedimentation.

50 Light Earth Building

Other methods for determining the plasticity are potentially more suitable, such as the determination of consistency limits according to Atterberg [DIN 18122 1997]. This test is likewise unnecessarily complex and, like the hand tests, open to subjective interpretation. It can also only be used for rich earth samples, is only an indirect indicator of the binding force, and is comparatively imprecise about the water content that the defined consistency of the specimen should have. Finally, the results do not correlate with the cohesion test [Krüger 2010] because the cohesion (binding force) of clay minerals is not dependent on the water content at a defined consistency but on their form (see above). In France, the Atterberg test is increasingly being replaced by the more reliable Methylene Blue Test, which is also equally suitable for both rich and lean earth samples. Testing the measure of shrinkage The measure of shrinkage of soils for construction when dry is ascertained using elongated test prisms (220 × 40 × 25 mm) that are made to a defined consistency (see [DIN V 18952 1956]). The degree of shrinkage cannot, however, be used as a means of classification, for example in binding force, because “each earth specimen has its own degree of shrinkage, even within the same classification, as a product of its chemical composition and texture” [Niemeyer 1946 p. 40]. Testing the cohesion of the fine soil fraction With very lean earth specimens, the cohesion test becomes problematic because it is difficult to make a test specimen of the necessary consistency. In such cases, one can obtain a more precise indication through an additional test of the cohesion of the fine soil fraction (clay and silt) without any sand particles. For this, one takes the washed out sediment of the fine soil fraction < 0.06 mm (see above) and dries it to the test consis­ tency before then undertaking a normal cohesion test [Volhard 2010a].

216

Testing slurryability

Because the earth is mixed with straw in a liquid form, the ease with which one can prepare an earth slurry, known as a clay slip, determines the effort and rhythm of later work. Lean earths in a crumbly, naturally-moist condition can quickly be used to produce a slip. Clay-rich earths, on the other hand, are more difficult to dissolve into water if added in a moist or wet state to water, rather than using dry powder. The slurryability test (Volhard): Take a handful of earth of the same consistency and moisture content as it will have later on the building site and place it in a bucket of water. If, after leaving it to soak and stirring occasionally, the clumps of earth only dissolve after several hours, or not at all, additional preparatory steps will be necessary (see chapter 310) or the earth mixture must be mechanically mixed.

Building materials for light earth  51 

Fig. 57 Crumbly dry earth

217

Fig. 58 Powdered earth

Sourcing earth for building

To be useful for building purposes, a sourced soil must be free of humus, roots and other organic material and must therefore generally be excavated from lower-lying soil horizons. Considerable cost savings can be achieved if the soil on the site is suitable for building purposes, even more so when obtained as part of excavations for a cellar: new earth material does not need to purchased and delivered, and the excavated earth for the cellar need not be transported away for disposal. One must, however, take care not to mix topsoil with the excavated material and to keep it relatively dry and protected from the rain – for example under a makeshift roof or in steep-sided heaps covered with water-repellent paper or plastic sheeting weighed down with planks. When excavating, the earth material should not be removed in great clumps but rather sliced off in thin sheets. If the earth on the building site is unsuitable or its horizon is too deep or too difficult to efficiently extract, a suitable earth can be obtained from elsewhere and transported to the building site. In the past, earth was often sourced from a particular location, as can still be seen in certain street and place names (e.g. Pit Lane, Quarry Bank). Nowadays it is also possible to source suitable earth from earth building materials producers and from brickworks. To avoid unpleasant surprises, one should find out the cohesion of the material from the supplier in advance. Earth is easiest to make into a slurry or slip when dry. Big bags should therefore be stored in a dry place and covered to prevent them becoming waterlogged with rain. Dry raw material from a brickworks must first be soaked. Some brickworks provide pourable earth material, which is ideal. Dry, crushed and powdered clay – used as a raw material in the ceramics industry – has both good cohesive properties and good slurryability. This high quality raw material can be worth obtaining for very lightweight – clay-rich – mixtures of light earth or to increase the cohesion of lean soils. Suitable soils can also be obtained cheaply as excavation material from road works or underground construction works, especially if directly sourced.

52 Light Earth Building

Fig. 59 Straw from a 700-year-old earth panel is still in a remarkably good condition, Gothic House in Limburg [Volhard 2010a]

220 Fibres and aggregates for light earth For light earth construction, the most common aggregates are straw, woodchip or mineral aggregates. Air trapped in the pores and cavities or the mix is responsible for the material’s insulating effect. Other fibrous, wooden or mineral aggregates are also possible, for example dry reeds, seaweed, rapeseed stems, coarse hay stems, heather, twigs, pine needles, flax shives or hemp hurds, cork, sawdust and wood shavings, pumice stone, foamed glass beads, perlite or ash. Fibres are better at stabilising the earth mixtures than mineral aggregates and lower its susceptibility to water erosion and frost (see figs. 321–323). Mixtures of the above are also possible. Flat, broad and rapidly perishable materials, such as greenery or leaves are not suitable.

221 Straw Given the large quantities of light aggregates required, it is simplest and cheapest to procure straw as an agricultural by-product. In bales, it is easy to transport and to stack. Bale straw usually has the right length of straw and does not need cutting or chopping for most building applications. When pressed into shuttering, the stems become a tangled mass that retains its shape so that the shuttering can be removed immediately. When sourcing straw, one should choose straw that is robust and resists tearing. It should be largely free of leaves and weeds so that it is less sensitive to moisture. For walls that are compacted or trodden down, wheat or rye straw is more robust than barley straw, which is softer and has flatter stems and is therefore more susceptible to settling. Soft straw is, however, better for use as floor infill and for making bricks or panels. Oats straw, coarse hay stems, straw and other fibrous aggregates can also be

Building materials for light earth  53 

nass Wet Anmachwasser Mixing water

trocken Dry

Earth Lehm

A

B

Straw-clay Strohlehm

A

A

Fig. 60 The stabilising effect of fibres

used for malleable application methods and for making earth reels, both of which cannot be made with wood-based or mineral aggregates. Straw from the year before that has been stored in a dry place is best.

222 Woodchip Woodchip is made of weaker wood without bark and is a by-product of lumber production in sawmills. It is used as a raw material for making cellulose and wood-based panels and can be obtained from sawmills or relevant wholesalers. The stability of woodchip light earth infill is a product of the adhesion of the woodchip material with the clay slip rather than the tangling of fibres. The coarse structure of the material is less suscep­ tible to moisture when drying conditions are unfavourable and can therefore be made in thicker layers. Light earth mixtures made with woodchip are inserted like straw-based light earth into shuttering, but need only be poured in and lightly compacted. Heavier light earth mixtures with a high earth slip content are stable enough for the shuttering to removed immediately and can be made with sliding formwork. Lighter mixtures require shuttering to remain in place for longer, and for this reason, permanent formwork such as reed lath is often used. Woodchip light earth settles only marginally and dries out slightly more quickly than straw-based light earth mixtures.

54 Light Earth Building

Fig. 61 Straw, an agricultural by-product

Fig. 62 Loosened bale straw

Fig. 63 Chopped or shredded straw, 20–30 mm

Fig. 64 Hemp hurds

Fig. 65 Woodchips

Building materials for light earth  55 

223

Mineral lightweight aggregates

All kinds of tuffaceous, porous natural stone of volcanic origins or artificially expanded or foamed materials of the kind used in conjunction with lightweight concrete, are suitable aggregates for light earth. Typical aggregates include pumice, expanded shale, expanded or foamed glass beads from recycled glass, perlite or expanded clay. The low bulk density of the material and its good insulating properties are achieved more through the porous quality of the aggregate than the interstitial spaces between them. As with woodchip light earth, the earth slip serves as a binding agent for the fill material. Granular aggregates can be mechanically mixed, poured and pumped. They require very little in the way of compaction, saving time during construction. Unlike straw-based or woodchip light earth, however, the shuttering must remain in place over the entire surface for several days until the earth slip is dry enough to hold them in place. Sliding shuttering is therefore not feasible. That means that to work fast and make optimum use of any available machinery, a lot of formwork is required in order fully shutter as many walls as possible in one go. Mineral-based light earths are less prone to settlement, but require a much greater density of aggregate material than both straw-based and woodchip light earth for the same bulk density (see fig. 106). In this context, one should also note that artificially produced aggregates such as expanded clay require considerable energy for their production. Originally made for loadbearing light concrete, they are in essence of an unnecessarily high-quality for light earth [Volhard 1990]. From an ecological viewpoint, mineral recycling material, such as granulated aerated concrete would be more conceivable. Fibrous aggregates can also be added to additionally stabilise the integrity of the wall mass and surface of mineral-based light earth constructions.

56 Light Earth Building

300 Preparation of materials for light earth 310 Preparation of clay slip If a slurryability test (see chapter 216) shows that the earth does not easily dissolve into a lump-free consistency, the sourced earth can first be left out to weather, soak or dry. Making use of the natural effects of sun, water, frost and time saves mechanical work. Only lean, crumbly earths will generally liquify without the use of mechanical aids. If necessary, the earth can first be broken down into a suitably crumbly state with the help of a soil shredder.

311 Weathering A few months before construction work is scheduled to begin, the sourced earth is laid out to weather in approximately 50 cm high beds with roughly 30 cm deep furrows, much like a ploughed field. Sun, rain and in particular frost will then break down the earth and make it loose and crumbly – as every gardener and farmer knows. In sunny weather, the beds can be watered from time to time with a watering can or hose to accelerate the process. With clay-rich soil, the larger the clumps the longer it will take to weather. One can reduce the time taken by properly extracting the soil – slicing the material from the ground in thin slices – in the first place. The process of weathering takes time – ideally over winter – but very little effort. Approximately 2 m² of ground are needed for 3 m³ of compacted light earth material.

312 Soaking A quicker alternative is soaking. This method can be used when there is neither the time nor space for weathering. The sourced earth is placed in approximately 50 cm deep pits with solid edging, or in containers 80 cm wide and 80 cm high, and covered with water. Here too, earth that has been cut from the ground in slices will break down more quickly. Larger clumps or chunks of earth should first be allowed to dry and be broken down before soaking (see below). The earth should be periodically broken down by thorough prodding with a pole, and after several days the clay fraction should be soft enough to be prepared to a slip through the addition of further water.

Preparation of materials for light earth  57 

Fig. 66 Earth spread out to dry

Fig. 67 Improvised drying rack made of euro-pallets

313 Drying Earths and clays of all kinds are most easily made into a slip when dry, as the open capillaries within the material absorb water readily. To this end, the earth should be covered with a transparent covering (e.g. a tent made of plastic foil) to protect against rain but allow the sun through. A space-saving variant is to dry the earth on suitable screens, latticework or another air-permeable mesh arranged in a rack on top of one another. The entire rack can be wrapped in foil or metal sheeting in such a way that air warmed by the sun can circulate from bottom to top through appropriate air inlets and outlets. Stony earths are less well suited for light earth construction but can still be used if there is no alternative. It is not necessary to separate out the stony particles through wet sieving or sedimentation. Instead, the earth can be dried as described and then thrown through an earth screen with a 10 mm mesh size (5 mm for machine pumping). Any large dry clumps can be broken down with a hand tamper or the wheels of a heavy vehicle or tractor.

314

Mixing by hand

For light earth construction, earth is mixed with water to form a pourable slip or slurry. Earth that has soaked in advance only requires more water adding to the same container. Naturally-moist, or ideally dry earth – break down large clumps first – can be pressed through a screen with 1 to 2 cm mesh size (e.g. a compost screen) into a water-filled container and then mixed well. Wait until the water has fully soaked into the capillaries of the material – i.e. when no more air bubbles rise to the surface – and then stir. Fine or pulverised clays or earths can be mixed directly without sieving. Mixing should take place in a container with solid base and sides, for example a lined oblong tank or trench, or mortar boxes or troughs of the kind used for slaking lime. To stir the mix one can use a lime stirrer, a robust rake or a rake with a steel flat welded to the end of the tines (Fig. 68). The latter is effective for churning the mix and the flat bar can be used to press out lumps against the bottom of the container.

58 Light Earth Building

Fig. 68 Trough and tools for mixing the clay slip

Fig. 69 Mixing by hand

Preparation of materials for light earth  59 

315

Mixing with an agitator

Various mixers of the kind used to stir and mix paints, mortars and emulsions are suitable for mixing a clay slip. Small quantities can be mixed with a hand-held mixer such as a heavy-duty power drill with paddle attachment (of the kind used for paint). Any kind of container can be used, but cylindrical containers are particularly well suited. For larger quantities, a mixing station is better comprising an electric motor that drives a vertical mixer shaft mounted on a crosspiece fixed to the top of an upright circular container which can be emptied at the bottom. The dry earth is added to the stirred water while the mixer is running. Because it mixes and disperses immediately, it may not be necessary to sieve the material first. The high rotation speed and mixing paddles break down any lumps and the resulting slip is ready for use in the space of a few minutes. Certain earths can wear down mechanical parts faster, and stones can damage the paddles. In practice, a geared agitator with a slow rotation speed (60 rpm) and horizontal mixer arms attached to the vertical shaft (figs. 72 and 73) has proven effective. The ­container can accommodate almost 1,500 litres and the slip is pumped out through a perforated screen via a pneumatic diaphragm pump (P. Breidenbach, Viersen). Large mixing machinery and intensive mixers of the kind used in the ceramics industry, which can mix up to 10,000 litres at a time, are only really feasible for the industrial production of light earth panels or bricks.

316

Mixing with a compulsory mixer

Simple mortar mixers, such as free-fall mixers or mixers with a rotating drum, are generally unsuitable for mixing earth because the mixer fins attached to the rotating drum do not effectively mix the slip. The earth will eventually turn to a slurry with water, but more through the presence of water than the action of the machine. Only dry earths (factory-produced in sacks) are suitable for slurrying in such mixers. Trough mixers and pan mixers on the other hand are suitable for use with liquid consistencies. These have a stable trough in which a horizontal or vertical mixer shaft drives suitably formed paddles (see fig. 96f). Plastering machines (diesel or electric) can be used not only to mix the slip, but also to pump it to where it is needed and to spray-apply it with the help of compressed air, reducing the labour involved considerably. Most of the compulsory mixers in these machines are designed for conventional plasters and clay-rich earths are problematic. The addition of an agitator within the mixing container – also a part subject to wear and tear – can improve the mixing process.

60 Light Earth Building

Fig. 70 Home-made tool with a section of pipe welded to a garden tool

Fig. 71 Paddle attachment for a power drill

Fig. 72 Geared agitator holding 1,500 litres, ­ emptied via a compressed air diaphragm pump (Lehmbau Breidenbach)

Fig. 73 The mixer arms of the geared agitator

Preparation of materials for light earth  61 

Fig. 74 PFT G4 compulsory mixer (Knauf) for

preparing the clay slip with dry earth material and subsequent pumping and spray application using compressed air (see project 27)

Fig. 75 Compulsory mixer with horizontal axis (Putzmeister P13)

317

Fig. 76 Thick viscous clay slip made of lean earth

Consistency of the clay slip

For normal use in light earth, the clay slip should be pourable and flow easily from the shovel which, after dipping in the slip, should remain evenly coated with slip. One should also verify that the aggregate fill material within the wall is likewise well coated with slip after insertion. While one may feel able to reproduce a good consistency (viscosity – fluidity) once found, a more reliable method of determining viscosity is to check its degree of spread (Volhard): 100 ml of slip is slowly poured with a steady hand onto a dry, non-absorbent surface of glass or metal sheet so that it spreads into a roughly circular film. The diameter of the spread defines the fluidity of the material (fig. 77).

62 Light Earth Building

Fig. 77 Checking the consistency of the clay slip by measuring its degree of spread Fig. 78 Thin slip made of rich earth Fig. 79 Stiff slip made of lean earth

Clay-rich earths have better cohesive properties and can be prepared as a thinner solution. Lean earths must be prepared in a semi-liquid to thick consistency in order to adequately bind the aggregates. As the water required varies for different kinds of earth, it is not possible to define specific mixing ratios. Thin slips can be easily poured, sprayed and mixed with straw without excessive effort. More viscous slips coat the aggregate more thickly and the mass becomes heavier and more difficult to work. Using a thin slip produces a lightweight, well insulating mass, while a thicker slip is good for making light earth panels and bricks that need a stronger structure. Slurries for earth masonry and plaster mortars must be stiff and pasty and no longer pourable.

Preparation of materials for light earth  63 

The drying time of the resulting mass depends on the water content of the clay slip. As a consequence, it is recommended to leave the light earth mass to dry for a few hours before use to allow it to reach a naturally-moist state (see chapter 335). The addition of a liquifying agent can reduce the amount of water required in the mix.

318

Liquifying agent

Liquifying agents (deflocculants) are used in the ceramics industry and in pottery to prepare casting compounds (casting slurries) that reduce the degree of shrinkage and shorten the drying time by decreasing the amount of water required. Of these, the most relevant are: −− Soda (Sodium Carbonate, Na2CO3) −− Water glass −− Ulmic acid −− Tannic acid or tannin These act as electrolytes that hold apart the crystalline layers of the clay mineral so that – put simply – they slide more readily over one another. Special liquifying agents such as Sodium Hexametaphosphate are also commercially available. These chemicals are used on their own or in combinations at proportions of between 0.1 and 0.4 % – ­re­­lative to the dry mass of the clay [Hamer 1975] [Weiss 1972]. The application of such additives can be used in light earth construction for a number of reasons: −− Better workability of otherwise excessively thick, slushy slips made of lean earth, −− A more even distribution of the slip in the straw mass when using less water, −− Faster drying time of the material due to lower water requirement. In a test series undertaken by the author, it was possible to reduce the proportion of water required for a slip of the same viscosity (fluidity) as a regular earth and water slip by up to 50 %. The reduction of the water content also means an increase in the clay proportion, and therefore an increase in the specific weight of the slip. Two agents were used: soda on its own and soda in combination with water glass in proportions of 0.1 % to 0.2 % with respect to the dry mass of the loess earth material. While a layer of water soon began to separate at the top of the earth–water specimen, the water remained bound within the slip preparations with added soda and water glass. In fact, after a few hours, they had become so thick that they could not be poured out of the beaker. A vigorous shake is, however, sufficient to restore fluidity. This phenomenon in which a slurry is only liquid when in motion but thickens when left to stand is called thixotropy [Hamer 1975]. The volume reduction of the dried slip preparations with additives is less than half of that of a regular clay slip. This would mean less volumetric shrinkage in building elements made with denser light earth mixtures, and would probably have the same effect with other wet earth building techniques, for example reducing cracking in plaster. Paper strips dipped in the liquid slip were more evenly and thickly coated than those dipped into a regular clay and water slip, in which the clay content gathered at the lower edge in a thick droplet (see fig. 80).

64 Light Earth Building

318-01

Clay slips of the sameFlüssigkeit liquid consistency Schlämmen gleicher

Probe Test AA

Probe Test B B

Lehm-WasserEarth-water slip Schlämme without additives ohne Zusatz

Lehm-Wasser-Schlämme Earth-water slip with added mit und sodaSodazusatz and less water geringerem Wasseranteil Pappstreifen* Paper strips* unmittelbar nachslip dem dipped into the immediately Anrühren eingetaucht after mixing

Originalfoto einsetzen. so aufhellen, dass Hintergrund weiss ist. Kein Rahmen

dipped slip after 10 minutes nach 10into minthe eingetaucht

*Fotos nach Trocknung * Photos take after drying

Volumenschwindung nach der Trocknung Volume reduction after drying Fig. 80 Test series using liquifying agent

The addition of these additives does not have a detrimental effect on the strength of the material. On the contrary, the increased proportion of clay particles raises it. Here too, it is impossible to give precise instructions on quantities and mixing ratios due to the differences in the kinds of earths. A short test can be undertaken to determine the correct and economical mixing ratios.

319

The addition of lime

Even a small amount of lime, when added to a normal fluid clay slip, can stiffen it to a curd-like mass. Lime acts as a thickening agent (flocculant) and a means of leaning down a mix. For light earth construction, the clay slip needs to be fluid and binding, and the addition of lime is therefore counterproductive. If one wants to improve the cohesion of a lean earth slip, one should add dry or pulverised clay (see chapter 217). In tests it was not possible to demonstrate a disinfecting effect on the structure through the addition of lime to the light earth mix. On the contrary, in unfavourable drying conditions the test showed increased mould formation.

Preparation of materials for light earth  65 

For straw-clay mixtures with a high clay proportion, the addition of lime may possibly help to lean the mix and reduce the degree of shrinkage and crack formation. If the earth is prepared not with water but with urine (from a horse), the result is a very firm weather-resistant building material that can be used without further treatment. This recipe was discovered in old chronicles by S. van Kessel (Belgium) who put it to use for the renovation of many half-timbered structures, most notably in Bokrijk Open-air Museum in Belgium. At the Katholieke Universiteit Leuven, the physical properties of this technique were investigated in a diploma project [Vanros 1981]. Urine and also dung improve the malleability of plastic mass considerably. This is also the secret behind the making of the paper-thin turned porcelain made in China [Weiss 1972] (see chapter 643).

320 Preparing fibres and aggregates

321 Straw For the best working properties, straw stems should have a length that corresponds to the smallest dimension of the building element, e.g. for compacted walls somewhere between 20 and 40 cm. In most cases, straw comes pre-bound in bales and has been broken down to approximately the right size for building purposes by the combine harvester and baler. Straw needs to be loosened and picked apart so that no nests of straw remain. One should prepare adequate quantities of loosened straw so that work can continue swiftly without interruption. Shorter straw with a length of 10 to 20 cm is useful for the preparation of heavy mixes with a high earth content, as well as for fashioning light earth bricks and blocks if no other short fibrous material is available. Straw that is too long is either: −− cut to size on a large chopping block using a broad-bladed axe or chopping knife, or −− cut with a scythe or knife by placing the straw on a table and cutting along the table edge (ideally with a metal edge), or −− clamping the entire bale in a suitably formed cutting rig and then slicing the bale with a long knife with a handle at both ends in a diagonal see-saw motion. Guides on either side ensure that that blade chops the straw to an even length (see fig. 85 after van Kessel). For shorter lengths, for example for straw-clay or for coarse and fine earth plasters, straw chopping or shredding machines can be used. Quite fine aggregate material can be produced with the appropriate sieve inserts.

322

Wooden aggregates

Woodchip does not need any special preparation. Other wooden aggregate can be chopped or shredded and then softened in water to reduce their bulk.

66 Light Earth Building

Fig. 81 Loosening the bale straw Fig. 82 Shredding machine Fig. 83 Straw cutting rig

Fig. 84 Chopping straw

Fig. 85 Straw cutting rig for short straw lengths of less than 30 cm (after van Kessel)

Preparation of materials for light earth  67 

331-01

Earth Lehm

Schlämme Slip

Straw Stroh

Spread out straw Ausbreiten des Strohs

Aufsetzen Stack Pour over slipmit Schlämme Übergießen

70 cm

Mix Mischen

Leave to soak Mauken

Turn over = =mix Umsetzen Mischen

331-02

Fig. 86 Spray method

Gießwerkzeug Tools for pouring

Mischwerkzeug Tools for mixing

Fig. 87 Mixing tools

68 Light Earth Building

330 Preparation of the light earth mix The light earth mix is prepared by mixing a clay slip of fluid earth as evenly and sparingly as possible with the aggregate so that all of it is evenly coated and the resulting mix has the colour of the earth. There are different ways of mixing the constituents which are more or less well suited for different aggregates: −− the clay slip is poured or sprayed over the aggregate material −− the aggregate is dipped in the clay slip −− the aggregate and earth are mixed together in a mechanical compulsory mixer (also in a naturally-moist state)

331

Spray method

The spray method described here using straw is in principle the same for other aggregates such as woodchip. Straw-clay and fibre-clay mixes can also be stacked in layers and raked through in the same way. To begin with, the clay slip and a stock of loose straw should be placed within easy reach. The straw is placed on a firm flat surface and spread out by hand or with a pitchfork into a 10 or 15 cm thick layer. The clay slip is poured sparingly over the layer of straw and the process repeated until a total of 5 to 10 layers has amassed, resulting in a heap about 50 to 70 cm high. The slip can be poured with a scoop shovel or a scoop or ladle mounted onto the end of a long broom handle. The slip can be distributed more evenly using a watering can with a spreader attachment of the kind used for liquid fertiliser. This can easily be fashioned out of a piece of metal (fig. 87). The watering can must be large enough as small lumps may clog a narrow spout. The process is quicker when working in twos: one person spreads out the straw while the other pours the clay slip over it. Once the pile is high enough, it is turned over using a fork or strong rake, working from the sides. It is sufficiently mixed once all straw stems are evenly coated with the slip. The final mass resembles a small muck heap. A well-prepared heap may only need turning over once. Experience shows that the clay can be distributed better in large heaps than in smaller quantities, and is less labour-intensive. Spraying the slip more finely over the spread-out straw can speed up the process considerably. For this one needs a machine pump and hose with which to pour or spray the slip, with or without a spray attachment. Suitable pumps include diaphragm, spiral or piston pumps. Typical plastering machines generally comprise an assembly of compulsory mixer, pump and air compressor and are ideal for conveying the clay slip for the light earth mass.

Preparation of materials for light earth  69 

Fig. 88 Pouring over the clay slip Fig. 89 Clay slip prepared in a plastering machine

is sprayed over each layer of spread-out straw Fig. 90 Mixing the light earth

Fig. 91 Spray method: clay slip prepared in a paddle mixer and pumped under pressure from temporary slip tanks is spray applied over the straw (Rheinländer)

70 Light Earth Building

Using a spray head and compressed air, the slip can be so finely distributed over the straw that it may not be necessary to mix the mass afterwards. The use of a pump and hose also makes it possible to transport the heaviest part of the light earth mix to wherever it is needed. This enables one to mix the light earth in the room or storey where it is needed (see fig. 111). In such cases, care should be taken to prevent water trickling through and soiling the ceiling below if it is to be left exposed, for example by mixing in a tub or trough.

332

Dipping method

The dipping method can likewise be used both for straw and woodchip light earth. The clay slip is poured or pumped into a trough or tub with a solid base. This is not necessary if the slip was already mixed in a suitable container. The aggregate material is then added and trodden beneath the surface wearing wellington boots until all the slip is evenly distributed from below. The straw must be well loosened in advance. The mass is then removed with a pitchfork and left to rest on one side. Other suitable containers include transport containers or vats (see fig. 92). If straw-clay or a similar fibre-based mix is to be prepared by dipping, the slip must be suitably thick and viscous. Alternatively, one can use a thinner slip and then leave it to rest and dry for longer until it has a malleable consistency. Small quantities of straw or coarse hay for applying by hand can also be simply briefly dipped – like pommes frites – in the slip and then used either immediately or later.

Fig. 92 Dipping method in transport containers, delivered to the site ready to use

Preparation of materials for light earth  71 

Stroh Straw

Lehm Earth

Einstreuen des Strohs Pour in straw

Schlämme Slip

Untertreten des Strohs Tread in straw

Soak Mauken

gemischter Leichtlehm Remove mixed light earth

Fig. 93 Dipping method

Fig. 94 Dipping method mixed in a lime-mixing

trough

72 Light Earth Building

Fig. 95 Dipping coarse hay

333 Mixing in a compulsory mixer Light earth made from bale straw is easier to mix by hand. In normal mechanical mixers, the straw tangles up with the insides and filling and emptying the mixer becomes laborious. A few specific kinds of machine, for example a tumbler (see figs. 100 to 102), are suitable for machine-processing straw-based light earth (for further examples, see projects 7, 18, 19, 20 and 26). Chopped straw, woodchip, other short-fibre material and mineral aggregates can be mixed with the clay slip in a normal compulsory mixer, for example in the same one used for mixing the clay slip (see above). The order of addition would be water, earth material, aggregate. Straw-clay and fibre-clay mixes made with short fibres can also be mixed with such machines. Feeders and modern mixing plants (fig. 103) can be used to very finely distribute and coat the aggregate with clay in a naturally-moist (i.e. not fluid) state. This has the advantage of requiring much less water. This material can be sourced from manufacturers and is delivered ready to use on site in the desired composition.

Fig. 96 Plastering machine (compulsory drum mixer)

Fig. 97 Mixing woodchip light earth with a series

with spiral pump for preparing clay slip and mixing of fibre or woodchip based light earth or earth mixes and light earth mortars (Putzknecht)

of paddle mixers (Diem). Transport and filling into formwork using a crane bucket. Via Felsenau, Bern, CH 1993

Fig. 98 Mixing using vertical-axis paddle mixers

Fig. 99 Mixing woodchip light earth in a paddle

(Felsenau project)

mixer

Preparation of materials for light earth  73 

Fig. 100 Mixing straw light earth in a tumbler drum mixer. The inclined rotating drum is open at both ends. Straw is inserted at the top and clay slip sprayed in through nozzles in the drum. The light earth mix can be removed continually at the bottom of the drum. The very rich clay makes it possible to use a very liquid slip and to prepare very lightweight mixtures. See project 20 (Design Coalition Wisconsin USA).

Fig. 101 Transporting the light earth mix using a skid steer loader

Fig. 102 Tumbler drum mixer by Oskam V/F, Lekkerkerk, Holland

Fig. 103 Feeder system for ­ anufacturing earth, woodchip m light earth and earth mortar mixes (Claytec®)

74 Light Earth Building

334

Mixing proportions

The mixing proportions of the light earth mixture depends on the desired properties of the building element. The lower the earth content, the lighter the resulting mixture and the better its insulating properties. As the proportion of earth increases, the heavier the mix becomes and the better its sound insulation, thermal retention capacity and fire-resistant properties. As a rule: Lightweight mixtures (300 to 800 kg/m³) = good thermal insulation with adequate thermal retention capacity and noise insulation for: −− external walls −− roof insulation −− floors and walls adjoining unheated spaces −− thermally insulating internal wall linings −− internal partitioning walls −− making bricks and blocks. Heavy mixtures (800 to 1,200 kg/m³) = good thermal retention capacity and good noise insulation, better stability (densities above 900 kg/m³ can hold nails and wall plugs) for −− internal walls −− intermediate floors −− external building elements with additional insulation layers −− making bricks and blocks. For heavier mixtures, the clay slip is made more viscous; for lighter mixtures the clay slip should be as fluid as the adhesive properties of the earth will allow. Very lightweight mixtures can only be achieved with a clay-rich slip (see above). The level of the bulk density of the mixture is therefore primarily a factor of the proportion of earth within it and less the quantity of the lightweight aggregate that acts as the inner skeleton of the wall, because the earth material fills the voids to a greater or lesser degree. Fig. 104 Bulk densities depend on the mixing proportions of straw and clay

Test blocks with the same quantity of earth and different quantities of straw Mass by volume 4 450 kg/m3 3 600 kg/m3 9 950 kg/m3 19 2,000  kg/m3 (no straw)

Preparation of materials for light earth  75 

Heavy mix (1,200 kg/m³)

Lightweight mix (600 kg/m³)

Surface

Section Fig. 105 Heavy and lightweight light earth mixes

With the same straw content (70 kg/m³) one can make both lighter and heavier light earth mixtures. In light mixtures, the aggregate is coated with just enough earth to stick it together. Here a clay-rich fluid slip should be used in combination with robust and bulky straw stems. The stems should be coarse, long and largely intact so that they present as small an inner surface area as possible for the earth to coat. With a clay-rich earth, the slip can be very thin, but with lean earth it needs to be thick enough to sufficiently adhere to and embed the straw stems. The dry bulk density also depends on whether the material is compacted or simply loosely pressed into the form, leaving more space for air cavities. Loose compaction in which the material is just pressed into all corners of the form can reduce the bulk density by around 20 %. The mixing proportions for light earth are shown in fig. 106. The actual quantity of earth added is in reality slightly less due to the air present in the non-compacted, crumbly material. 10 kg of straw corresponds roughly to the size of a pressed bale. The dry bulk density of a light earth mixture increases with the weight of the dry earth content. As the same quantity of dry earth material can be mixed with different amounts of water – depending on the earth content, any liquifying agents and the

76 Light Earth Building

Dry bulk density Aggregate

Lightweight mix 600 kg/m³

Heavy mix 1,000 kg/m3

Density

Dry earth proportion1)

Earth required, crumbly, poured2)

Dry earth proportion1)

Earth required, crumbly, poured2) m3/m3

kg/m3

kg/m3

m3/m3

kg/m3

Straw

70–90

520

0.4

920

0.7

Fine fibres

150

450

0.3

850

0.6 0.5

Woodchips

300

300

0.2

700

Foamed clay

350

250

0.2

650

0.5

Pumice

600

 –

 –

400

0.3

1)  Earth proportion = bulk density – aggregate density (kg/m³) 2) Earth required at a dry pouring density of 1,400 kg/m³ Earth required = earth proportion / dry pouring density (m³/m³)

Fig. 106 Mixing proportions for 1 m3 compacted light earth

desired consistency of the slip – the quantity of slip is not as relevant for the dry bulk density as the amount of earth material it contains, because the mixing water evaporates. While this can be determined in an experiment with test cubes for particular mixing ratios, it is hard to reproduce with any degree of precision on the building site, and also complex to measure. With a little experience, however, mixing ratios can be judged intuitively as follows: Light mixtures are much easier to lift and the straw rustles during mixing. After insertion into the formwork, a high proportion of voids remain in the mass, which are evident after removal of the formwork on the wall’s surface which resembles that of wood-wool panels. Heavier mixtures are harder to mix. The viscous sticky mass is denser when pressed into the form, and the surface texture flatter after removal of the formwork (fig. 105). The actual dry bulk density can be determined and verified by making test cubes (see chapter 735).

335 Tempering The final light earth mixture should be allowed to temper (to seep in) for a period of between 6 and 24 hours, protected from direct sunlight and premature drying out. The mixing water can seep into the earth and aggregate and the mass returns to a moist, somewhat sticky mixture that is easier to work. Practice has shown that it is sometimes possible to skip this stage and begin immediately with filling the wall panel, especially when a liquifying agent has been used and the mixture therefore requires less water. If, however, the mass is springy when compacting it, or the clay slip drips out of the bottom of the formwork, then the mixture should be left to stand for a while longer. Mixed straw-based light earth should be used within eight days, woodchip light earth within three weeks. Heaps that have begun to dry on their surface can be used immediately if slightly wetted using a watering can and worked through. Material that has fully dried can also be re-used with the renewed addition of water or clay slip. It is also possible to spread

Preparation of materials for light earth  77 

Fig. 107 Straw light earth mix

Fig. 108 Woodchip light earth mix

out thin layers of pre-mixed (woodchip) light earth mixture to dry. The dry product can be stored indefinitely and used either dry in permanent (lost) formwork or slightly wetted as usual.

340 Organisation of the building site Transporting light earth is not heavy work compared with transporting stones, mortar or concrete. Straw light earth can be lifted and thrown with a pitchfork and transported in a wheelbarrow to where it is needed. For light earth mixtures with lumpy or granular aggregates (woodchip and mineral light earths), one can use a multi-tine fork, shovel or bucket. The mixing floor should nevertheless be located as close as possible to where the material will be needed and should be protected from the rain, as should the storage areas of the earth material and straw. In wet construction, the mixed material is transported at ground level via wheelbarrow or onto an upper storey via an inclined elevator that can also be set up at a steep angle within the building structure. Alter­ natively, the mass may be lifted onto scaffolding with the help of a crane. Fine fibrous or granular light earth mixtures can also be poured directly into formwork from a crane bucket, or pumped to where it is needed. Spray application is similar in principle to shotcrete and requires a compulsory mixer, pump and hose so that the light earth material can be spray-applied directly onto the wall (see chapter 460). Manual transport on the building site, especially when working on upper storeys, can be made easier in small projects by transporting the aggregate and earth individually to the place where it is required: −− Straw is lightweight, is convenient to carry in bale form and can also be thrown directly from the back of a lorry onto the upper storeys. −− Earth, when dry is as light as it will ever be and can be transported with the usual means (wheelbarrow, bucket, winch and crane). −− Water accounts for around a third of the weight of the mixed light earth material, but in its pure state can be delivered directly to upper storeys via hosepipe.

78 Light Earth Building

Schubkarre, Wheelbarrow, Gabel, fork, lift, crane Aufzug, Kran Lehm Earth

Stirring Rührenand + mixing Mischen A Transportation mixed light earth A Transport desofLeichtlehms

Bucket, Eimer, pump Pumpe

Mixing Mischen

Stirring Rühren

B Transport der of Schlämme B Transportation mixed slip

Wheelbarrow, Schubkarre, bucket and Rolle + Eimer, winch, Körbe, Kran basket, crane

Rühren + Stirring and mixing Mischen

Wasseratmit Water mains Leitungsdruck pressure C Transport desofLehms C Transportation earth material Fig. 109 Alternative approaches to transporting materials on site

−− Clay slip (= earth and water) as the heaviest constituent of light earth can be delivered to where it is needed with the help of a pump and hosepipe (e.g. using a plastering machine or sludge pump). The light earth is then mixed within the building construction as close as possible to where it will be needed. The clay slip can also be prepared there. A further advantage is that work is protected from the elements by the frame construction and roof, obviating

Preparation of materials for light earth  79 

Fig. 110 Inclined elevator inside a building

Fig. 111 Mixing inside the building. Spraying the straw with pumped clay slip (see project 2).

the need to erect temporary weather protection measures outside the building. The choice of approach depends on the respective local conditions on site and the extent of building work to be done.

350 Ready-mixed material Light earth mixtures made with straw, woodchip or mineral aggregates can be sourced ready-mixed from earth building materials producers. This obviates the need for most if not all of the preparatory steps from extraction of the earth and testing to building site organisation. 1.3 m³ poured straw light earth produces around 1 m³ of compacted material in the wall. In the case of woodchip light earth, the relationship is 1:1. Ready-mixed straw light earth should be used within a week. Woodchip light earth is less moisture-sensitive and can be stored for longer. The delivered material should nevertheless be covered up and if it has already started to dry may need wetting or mixing with additional clay slip as required. Dry mixtures can be stored indefinitely and need only be mixed with water when required on the building site.

80 Light Earth Building

400 Wet construction 410 Shuttered walls In a loadbearing timber construction, a pre-prepared light earth mix is inserted ­between shuttering made of sliding formwork, full-surface formwork or lost formwork and compacted into a solid mass. Sliding formwork can be used with straw light earth, which becomes sufficiently firm on compaction, as well as with heavier woodchip light earth mixes, and makes it possible to work continuously without having to wait for the mass to harden after each lift of the formwork. Lightweight woodchip light earth mixes and mineral light earths need to harden before the formwork can be removed (see chapter 415). External walls can be constructed as a single layer – rendered or clad – up to a thickness of 30 cm. Thicknesses greater than 35 cm dry slowly and are therefore not advisable for wet construction methods. Better insulation can be achieved with thicker walls made of light earth masonry or by using additional layers of insulation, either applied afterwards or used as lost formwork for the light earth mix. 5 cm thick reed boards have proven effective (see also chapter 811). Internal walls with a thickness of 10 to 15 cm are sufficient to act as a thermal mass and good sound insulators.

Fig. 112 Timber post construction with set-back external walls (architect: M. Bönisch, Windeck)

Wet construction  81 

The timber frame construction serves several purposes: −− it is loadbearing and stiffening −− it provides a frame for the space enclosing surfaces −− it defines the wall thickness and can serve as a slide rail for fixing shuttering The loadbearing framework is designed to meet the structural requirements and must be structurally stable in its own right without the panel infill. Other skeleton frame constructions and materials – e.g. steel or concrete – are also conceivable. All common timber construction methods are suitable for infilling with light earth. When using shuttering, the fewer horizontal members there are in the framework, the more straightforward the filling and compaction process will be. The loadbearing posts of the structural timber frame can be spaced at wider intervals. Between them, a slenderer supporting framework can be erected at spacings of no more than 1.50 m to provide adequate fixing points for formwork and to prevent it from bulging outwards. The wider the spacing, the more substantial the formwork will need to be, the closer the spacing, the lighter it can be. More closely spaced supports can also be used later for fixing cladding. If the panel infill ends mid-panel in the vicinity of a column, stakes (battens, branches or boards) should be loosely laid in the mixture during compaction to secure the infill to the column and to prevent the formation of vertical cracks (fig. 116 A + D, fig. 117 A to D).

411

External walls

A – Loadbearing posts in the wall core The vertical posts are completely enclosed by the light earth material. Here cheaper round timber posts can be used. The slide rail can be temporarily fixed and removed later, but in such cases a horizontal lath should be laid in the wall at height intervals of 40 to 50 cm. For a continuous wall surface, the slots left after removal of the rails should be filled with light earth material. B – Loadbearing posts flush with one side of the wall Here the vertical posts of squared timber can remain visible, either on the inside or the outside. The slide rail is nailed or screwed to the other side and remains in the wall to hold the panel in place within the wall. This method can be used to provide seamless insulation along one face of exposed half-timbered constructions. C – Twin loadbearing posts Twin loadbearing posts secure the panel infill and serve as fixings for the shuttering without the need for additional slide rails. If planed, they can remain exposed on both sides of the wall. Prefabricated shuttering supports with a double-T cross section can also be repurposed as twin posts and are available 20 and 30 cm deep. D – Loadbearing planks Planks, for example with 5/26 cm or 8/28 cm cross sections, likewise define the width of the wall without the need for a supporting construction. The panel infill is secured in place

82 Light Earth Building

Fig. 113 External wall made of 6 × 6 cm batten construction (architect: Martin Breidenbach, construction: Lehmbau Breidenbach) Fig. 114 Studwall construction with twin posts 6 × 10 cm, central post 10 × 10 cm, with twin beams and intermediate bracing (architect: F. Geelhaar, ASAD, Darmstadt, see project 4) Fig. 115 Slide rails outside and exposed loadbearing posts inside (architect: M. Böhnisch)

by nailing battens to the planks or by making long slots in the planks through which the light earth mixture is pressed. The thin planks are more susceptible to warping, which may result in gaps arising between the earth mass and the plank. These may need to be plugged once the wall is dry. Planed planks can serve simultaneously as window or door linings. Non-loadbearing ladder or plank studs The supporting stud framework remains in the wall to stiffen the light earth infill material and to connect it to the timber construction. These studs can take the form of a ladder, plank or twin post. Ladder studs are fashioned out of two 40 × 60 mm battens, nailed or screwed together. The wider the column spacing of the loadbearing

Wet construction  83 

411-05

Loadbearing posts (timber frame) Tragende Stützen

A Posts in im theWandkern wall core A Stütze

Non-loadbearing framework Nichttragende Stützen (Füllskelett)

Ladder studs Leiterständer

B Posts on one side B Stütze einseitig of the wall

C Doppelstütze C Twin posts

D Plank studs D Bohlenständer Fig. 116 Timber frame construction principles of external walls and thick internal walls

84 Light Earth Building

412-01

Loadbearing posts (timber frame) Tragende Stützen

Non-loadbearing framework Nichttragende Stützen

A

B

C

D Fig. 117 Timber frame construction principles of internal walls and thin external walls

Wet construction  85 

structure (upwards of 3 metres) the stronger the battens should be, or the more closely spaced they should be (figs. 116 and 117 A to D). In the case of twin post or ladder studs, the connecting crossbar should ideally be arranged flush between the vertical battens so that any light earth settlement does not result in holes that extend the entire depth of the wall.

412

Internal walls (and thin external walls, 10 to 15 cm thick)

Squared timber and plank studs Squared timber studs are used to support loads from floors above and as fixings for internal doors. Between them, plank studs should be arranged at intervals of about 1 metre. Lateral pressure acting on the panel face is transmitted via horizontal battens laid loosely in the light earth mass into the columns where they are held in place via battens nailed to the columns prior to filling (fig. 117 A + C), or via notches cut into the vertical posts (B). The number of stiffening horizontal battens required is a factor of the distance between the columns and the wall thickness: approximately 3 battens or 2 planks per m² (see draft norm DIN V 18953 Sheet 5). Thinner external walls with low insulation requirements, for example for outbuildings, or walls with additional thermal insulation can also be constructed in this way. Prefabricated elements For thinner walls, and therefore lighter weights, it is possible to prefabricate the wall elements including fill material lying on the ground and then to turn the entire wall element upright, together with the backing formwork.

Fig. 118 Internal wall infill using wet construction

86 Light Earth Building

Fig. 119 Internal wall infill once dry (see project 2)

413 Formwork Sliding or climbing formwork is attached to the timber construction and slid upwards with each new section of walling. The vertical frames hold the formwork panels apart and act as vertical slide rails. The formwork panels are 50 cm high, but should always cover the existing compacted wall by about 25 cm to prevent it bulging when new material is compacted from above. Each batch – or lift – is therefore 25 cm high. The formwork panels should be as light as possible. Most formwork panels for concrete are 150 × 50 cm and easy to handle. If one uses 25 cm boards, planks or narrower concrete formwork panels, tie rods can be inserted wherever it suits in the slot between two panels. A strip of wood fixed to the end of the formwork panel can serve as a butt plate to hold the next formwork panel in the same plane, reducing the need for renewed insertion of a tie rod (fig. 120). When shifting a formwork panel upwards, it should be drawn to one side or shifted upwards so that straw stems are not pulled out of the wall in the process of removal. Formwork that has become stuck to the wall should be removed with a determined jolt, and not forcibly whacked free of the wall. Formwork is easier to remove when the surface is kept clean and is wetted before filling with light earth. The formwork is either screwed to the supports or pressed against the wooden rails with typical tie anchors. These are not needed in great quantities and can be made oneself or hired for the duration of construction. As the formwork is shifted upwards – lifted – with each batch, the anchors need to be easy to loosen and re-tension without

413-01

Fig. 120 The principle of sliding formwork

Slide rail, crossbar Gleitlehre Abstandhalter Board to distribute Brett zur clamping force Druckverteilung

25

cm

Strut evtl. where necessary Spreize

Satzhöhe Lift height

25

Anchor Anker

Schalbretter Shuttering boards

Stoßlasche Batten as retaining lip

Wet construction  87 

414-01

Schaltafel Shuttering board, 50 cm or oder 50 x× 150 150 cm 50 cm 50 x× 200 200 cm

25

A Simple shuttering A Einfache Tafelschalung

Joch geschweißt Yoke, welded a) a) oder ausofHolz b) b) or made wood

25

Shuttering Schalbrettplank, 25 25×x150 cm 150 cmoroder 25×x200 cm 200 cm 25

a)

b)

B Schalung with mit beweglichem B Shuttering mobile yoke Joch

Schaltafel board, Shuttering 50 ×x150 cmor oder 50 150 cm 50 ×x 200 cm 200 cm 50 Variant: clamping Variante: with wedges Befestigung mit Keilen

C Shuttering with wall-high yoke Joch C Tafelschalung mit wandhohem

Fig. 121 Wall shuttering systems (timber construction not shown)

88 Light Earth Building

414-02 Release entspannen

Shift umsetzen

Retension spannen

A Simple shuttering A Einfache Tafelschalung

oberster Satz unter Final lift under ceiling geschlossener Decke

B Schalung with mit beweglichem B Shuttering mobile yoke Joch

Full-height einseitig voll shuttering on eingeschalt one side

Tafelschalung mit wandhohem CC Shuttering with wall-high yoke Joch Fig. 122 Different approaches to working with sliding formwork

Wet construction  89 

suitable for geeignet für Schalungssystem shuttering systems A

a) A  Anker nchor made of hardwood aus Hartholz Sperrholz mit oroder plywood with hardwood Hartholzkeilen wedge

b) Metal Säuleneisen b) column clamp (Schürmanneisen)

c)   self-cleaning elbstreinigender Sselbstreingender threaded rod c) Gewindestab mit Flügel/ Flügel/ with winged or hex nut Sechskantmutter

A

Ø 15/17

ABC

Fig. 123 Formwork anchors

requiring special tools. An overview can be seen in figure 123. Tensioning with the typical wedge and pop-up catch mechanisms is only possible one after the other using a tensioning device. This device is, however, all too often never to hand when one needs it. Self-cleaning threaded rods (c) of the kind commonly used for concrete formwork can be tensioned on both sides. The winged nuts are also quick and easy to loosen and re-tension if the thread pitch is sufficiently steep. The tension rods should not protrude too far out of the wall to prevent injury. Screw clamps and shuttering clamps (tensioned with a hammer) are further versatile tools to have on site. Shuttering clamps can in some situations replace the need for tie rods altogether. Toolbelt loops help keep portable tools – tensioning device, carpenter’s hammer or cordless screwdriver – to hand when shifting formwork panels.

414

Formwork systems

A – Simple formwork The approximately 150 × 50 cm large formwork panels are attached directly with tie rods. The panels are pre-drilled with a series of holes for receiving the anchor, or a slot if made of several timber planks. With each lift, the tie rod is released and removed, the panels shifted upwards and held in place until the tie rods are reinserted and tensioned. To press the panels more evenly against the wall, a backing plate (a piece of plank or batten) can be clamped in with the tie rod. This simple system is somewhat unwieldy to handle, but perfectly satisfactory for smaller building sites. B – Formwork with movable yoke This system makes it easier to raise the formwork by making it possible to release and re-tighten the individual formwork elements individually so that nothing need be put

90 Light Earth Building

aside or held in place manually. The tie rod is threaded between the slot between the two 25 cm wide planks panels on each side and the panels are clamped in place with the movable yoke. The process for each lift is as follows: −− The lower tie rod is released and removed and threaded into the upper end of slot in the yoke but not yet tensioned. −− The central tie rod is loosened, the yoke slid upwards, and the tie rod re-tensioned. This is now the lower tie rod. −− Once the last yoke has been shifted upwards, the lower formwork panel can be removed and inserted from above between the side rails and yoke. −− The top tie rods are now tensioned. The slot in the yoke must be at least three times the diameter of the tie rod longer than the sum of the formwork panels it bridges. C – Formwork panels with wall-high yoke With this system, the formwork panels are not removed but shifted upwards once the yoke has been loosened. Because they don’t need to be manually handled they can be longer (e.g. 200 × 50 cm). Only the top yoke tie rod is loosened and re-tensioned, and is raised one or two steps higher as wall construction progresses. The bottom tie rod is left tightened (see figs. 118 and 127). It is also possible to position the vertical yoke set back from the formwork panels and to clamp the panels in place with hardwood wedges inserted between the yoke and formwork. One side of the wall can also be shuttered Fig. 124 Shifting a formwork

panel

Fig. 125 Shuttering panels with yoke, 2 × 50 cm Fig. 126 Lightweight shuttering, 2 × 25 cm with mobile yoke

Wet construction  91 

Fig. 127 

Wall-high yoke with sliding formwork

Fig. 129 Screw-on shuttering

Fig. 128 Plank shuttering

over the entire height. This has the advantage of being able to work almost continually with only short breaks for each lift (see figs. 118 and 127). D – Plank formwork Two planks on each side are clamped in place with a tie rod and vertical wooden or metal profile to apply even pressure (fig. 128). The lift can be achieved more simply by using a second set of tie rods and clamps and a third pair of planks. For the lift thereafter, the lower plank and tie rod assembly is brought to the top. E – Screwed formwork The formwork panels are fixed directly to the vertical timber construction with quick-drive screws with hex-bolt or hex-socket head and washer. Cordless screwdrivers make this a quick process. This system is particularly suitable for formwork fixed to one face of the wall. As it is fixed directly to the vertical rails, these must be securely fixed to prevent them coming loose during compaction, for example with wire ties or perforated metal connecting strips (see figs. 134 and 201). Using the light earth technique, it is possible to complete entire wall sections one after the other (fig. 130). In addition, the amount of formwork and scaffolding required is comparatively small: 8 formwork panels and 12 tie rods can be enough for an entire house. If shuttering and compacting several walls in a ring at once, more form­work is

92 Light Earth Building

414-09

2

1

Gerüst Scaffolding

Gerüst Scaffolding

Gerüst Scaffolding

3

Fig. 130 Sequence of shuttering and compaction of wall sections

required but it allows a larger group of builders to work more flexibly. As the wall sections have more time to dry between lifts, the walls also exhibit less settlement.

415

Walls with lost formwork

Lost formwork, also called permanent formwork, obviates the need to stop and reposition sliding formwork during insertion of the wet mass in the wall as it remains permanently in place after completion of walling. It typically takes the form of a layer of insulation or a plaster base and is well suited for use in conjunction with very lightweight straw or woodchip light earth mixtures. Reed plaster lath Reed plaster lath serves as lost formwork, retaining the mixture in place while also allowing the wall to dry. It also acts as a plaster base for very lightweight mixtures. A reed plaster lath with 70 stems-per-metre is successively unrolled as work progresses and stapled to the timber construction with zinc-plated narrow gauge wire (fig. 133) [Breidenbach-Röhlen 1993]. This material requires that the vertical supports are placed closer together at a spacing of about 30 cm to prevent bulging and is used particularly successfully for light earth wall linings on the inner surface of historical half-timbered structures (figs. 200–202).

Wet construction  93 

Fig. 131 Lost formwork for woodchip light earth using reed plaster lath Fig. 132 Reed plaster lath fixed with additional galvanised wire Fig. 133 Commercial building with woodchip light earth wall infill behind reed plaster lath (Claytec®)

Lightweight insulation boards An additional layer of insulation can be applied to either the internal or the external face of the wall construction depending on the desired thermal insulation effect. The material should be vapour permeable and capillary conductive to facilitate the drying of the building element. 5 cm thick lightweight reed insulation boards, for example, provide relatively good thermal insulation and also double as a plaster base (fig. 135). Care should be taken with multi-layer lightweight insulation boards, as they are not capillary conductive. Due to the slower drying time, the thickness of the light earth layer should in all cases not exceed 15 to 20 cm. The building element is filled from the opposite side with the help of sliding formwork (fig. 134). The timber construction should be designed to ensure the light earth infill is properly retained within the wall. Timber planking Because wooden planks warp when exposed to the moisture within the wet material, and because they prevent effective drying, timber planking is not recommended for use as lost formwork for wall surfaces. Latticework Lattices made of spaced battens do not prevent drying and can be used as “lost climbing formwork” on the filling side and across the entire face of the building element

94 Light Earth Building

Dämmplatte als as Insulation board verlorene Schalung lost formwork

DistanzDistancing rohr piece auf Ständer a)a)  S  huttering screwed togeschraubte vertical studs Schalung

inseitige b)b)C  elimbing formwork on one Kletterschalung side without slide rails ohne Gleitlehren

Fig. 134 One-sided sliding formwork

Fig. 135 Woodchip light earth behind reed insulation board Fig. 136 Laths as lost formwork

on the reverse side. The battens should not cover more than 50 % of the wall’s surface. This method can also be used for very lightweight light earth mixtures. Window and door linings Window and door openings can be shuttered with planks or lined with lost formwork made of plasterable lightweight insulation board, water-impervious plywood or similar (see chapter 650). Horizontal lining boards beneath windows can also be inserted after inserting and compacting the light earth mass.

Wet construction  95 

416 Compacting the light earth mix The light earth material is filled into pre-wetted shuttering, distributed evenly and then pressed firmly into the shuttered form. Straw light earth is light enough to be thrown into the shuttering with a pitchfork from the floor. Wherever possible, the material should be filled right up to the upper edge of the shuttering, then spread evenly throughout the shuttering and into the corners (Fauth recommends using small forks for this: see figure 35) before being compacted, working from the corners and edges inwards. After two to three iterations of filling and compaction, the formwork can be shifted upwards. If too little material is filled into the shuttering and then compacted before adding more, horizontal layering occurs which is less good at sustaining the mass of the wall material above it, resulting in settlement of the panel. Woodchip and mineral light earths can be filled with a manure fork, shovel or bucket. In many cases they can be pumped or poured in from above using a crane bucket. Tampers can be fashioned out of 30 to 60 cm long sections of plank or batten (4 × 6 cm) rounded at one end to form a handle. They soon acquire a healthy coating of handfriendly earth. Light earth is pressed into the shuttering and plugged into all corners. Greater emphasis should be given to ensuring an even distribution of the aggregates than on achieving a high degree of compaction. It is not necessary to compact too firmly or for a long time. Straw light earth can be compacted layer for layer until the height of the wall is reached. If the mass is only lightly pressed down, for example for very lightweight mixtures, one should wait before shifting the formwork – at least upwards of a certain height to prevent the wall below, which still has room for compaction, from bulging. Alternatively, one can employ lost formwork (see above). One can connect successive work stages by wetting the dry or partially dry light earth of an already completed section – or spraying it with clay slip – while wetting the formwork for renewed insertion. To plug gaps beneath horizontal parts of the timber structure – e.g. under horizontal rails, beams and wall plates – or the last part of the wall beneath the ceiling, the last formwork panel should stop short by about 15 to 20 cm and only the shuttering on the reverse be continued to the top. Using a short tamper, the viscous mass should be poked into the cavity with one hand, while the other hand holds a plasterer’s float to keep it from escaping (fig. 139). The final hole can be plugged by twisting in the light earth in a screwdriver-like motion. One can also insert the mass by hand into the last corner and then nail a formwork panel over it that remains in place for one day before being removed. If the timber construction allows, i.e. is open from the top, the uppermost layer can be filled in from the floor above and compacted (fig. 122) or one compacts or inserts light earth bricks after the wall has dried. Holes and settlement gaps are best filled all in one go with viscous light earth after the panel has dried.

96 Light Earth Building

Fig. 137 Throwing in the mix with a pitchfork

Fig. 138 Distributing and pressing down the light earth is sufficient

30 c

60 c

m

m

416-02

4

6 4

Fig. 139 Plugging the junction to a ceiling or

horizontal timber member from the side

6

Fig. 140 Tampers

Wet construction  97 

420 Manual application Light earth walls can also be constructed without formwork. Much like the historical wattle-and-daub technique, a supporting framework of latticework or slats serves as a backing for the light earth material (see chapter 122). Depending on the respective application method, such walls can be between 4 and 25 cm thick. The straw clay or heavy light earth mixture (approx. 1,000 kg/m³) must have a sufficiently high earth content to be workable as a malleable mass. Freshly-prepared material should be allowed to stand until it is properly workable. An advantage of manual application is the ability to freely determine the depth of the panel infill with respect to the face of the timber structure, for example to receive a facing plaster that lies flush with the exposed timbers. Historical, good-quality straw-clay mixtures have a dry bulk density of between 1,100 and 1,400 kg/m³ and a remarkably high straw content of between 45 and 60 kg/m³ (cf. fig. 106). Some very old panel infill could be described as an early form of light earth [Volhard 2010a]. Even lighter traditional straw-clay panels of up to 800 kg/m³ can be seen in Belgium [Vanros 1981]. The quality always depends on the composition of the straw-clay. A manual for rural building construction notes: “The word ‘straw-clay’ is very old and denotes a ‘production procedure’ of great practical value and meaning that is, however, widely underappreciated. The material that goes by the name ‘straw-clay’ today is often just ‘some straw with earth’. Almost always, far too little straw is mixed into the earth mix … This straw-clay should be light enough to be handled with a manure fork like dung … There can never be too much straw.” [Grebe 1943] The supporting framework for straw-clay or light earth applications can be made in different ways: −− a wattle of stakes and woven willow rods −− stakes wedged between posts or beams −− latticework or lath fixed to the vertical timbers

Fig. 141 A high density of straw in an old infill panel

98 Light Earth Building

Fig. 142 Historical straw-clay preparation with a fork [Grebe 1943]

421 Wattle Wattle is traditionally made of willow or hazel rods woven between fixed oak stakes. The stakes are usually arranged vertically or parallel to the shortest side of the pane. Trimmed to a point at the ends, they are inserted in prepared holes at the bottom and firmly wedged into a triangular notch cut with a hammer and chisel or milled in the upper timber of the panel frame. Three stakes usually produce two easy to weave sections (fig. 144). The wattle can be arranged slightly off-centre (with respect to the depth of the wall) to make room for the thicker first application of earth material. The reverse side is usually applied more thinly and in historical half-timbered buildings, this is usually the (visible) face with exposed beams, i.e. the outer face for external walls or for internal walls, the face facing onto the less important room. The rods are cut with secateurs and woven around the stakes while still fresh. Rods that are too thick are split down the middle into two or three parts to make them easier to weave. Willows can be split using a willow cleaver, a small tool made of plum wood (fig. 271). It is also possible to fabricate or prefabricate wattles out of straight battens. In Japan, different thicknesses of bamboo cane are used tied together with string where they cross. The spacing of the mesh should correspond roughly to the straw-clay material used. For small mesh spacings – 2.5 cm or the thickness of a thumb – a straw-clay mix made with short lengths of chopped or shredded straw or hay is suitable. Wider spacings (5 cm or the thickness of a hand) and very wide spacings (10–15 cm or the width of a hand) correspond to long-stem straw or light earth with stem lengths of up to 30 cm. This is about the length of uncut bale straw. A short-fibre earth mass is applied with a trowel or float to one side and allowed to dry a little before applying from the reverse side. The first application should squeeze through between the rods and show on the other side. Long-stem straw-clay is worked in by hand. The following method has proven effective: Using a small three-tine garden fork, a suitable portion of the prepared material is scooped out, pressed together in both hands, and then thrown back vigorously onto the mass. The resulting flat ‘cakes’ are then laid on the horizontal rods Fig. 143 New wattle in a half-­ timbered construction, Elnhausen (construction: Lehmbau Breidenbach)

Wet construction  99 

2—5 a)

a)a)Dense wattle Enges Flechtwerk

b) wattle b)Open Weites Flechtwerk

c) Hooked over diagonally Schräge Auflagen

5—10

10—15

~45°

d) Wound wattle d) Wickelaround auf Geflecht

Fig. 144 Wattle and daub construction

in tight rows next to one another. Depending on one’s respective needs of preference, one of the following methods is then used: a) For thick walls (up to 25 cm), one takes roughly 5 cm thick pieces of light earth and inserts them at an angle of about 45° next to and on top of one another, wrapping the upper end around the wattle rods. On the reverse side a thin layer of fibre-clay is applied

100 Light Earth Building

Fig. 145 Daub applied to a ­tightly-woven wattle Fig. 146 Wrapping straw-clay onto a series of laths

Fig. 147 Long-stem straw-clay from bale straw, picked out with a hook

Fig. 148 Historical application of daub with a hook and float [Grebe 1943]

421-06 Fig. 149 Tools for manual application: hooks, hoes and hand-held floats

20—24

cm

14 c

12—

m

a)a)H  and-held Handbrettboard nach [Reuter [Reuter 1919] 1919]

12 cm

20

cm

c) G  arden hand c) Gartenhacke cultivator b) Wooden Holzbrettfloat b)

Wet construction  101 

like a layer of plaster, often after the thicker layer is dry. To achieve a flat surface, the earth material is struck flat using a small float while the earth material is still soft, flattening out uneven peaks and troughs in the surface. The resulting surface should be perfectly flat and ready to receive a facing plaster, and will not look any different to a shuttered infill panel. b) For thinner walls, suitably sized portions of earth material are taken and inserted so that they rest saddle-like next to each other on the wattle rods. The lower ends are pressed down onto the layer below or one draws them back and forth in an S-shape around the rod below. A thin layer is then applied from both sides and the surface struck flat and smoothened to achieve a perfectly flat surface.

422 Stakes Stakes can be used on their own as a fence-like arrangement of lengths of wood or battens that are wedged either horizontally or vertically into notches in the timber framework. These are then covered or wrapped with an earth mixture. As with the fitting of floor stakes (see below), it is advisable to complete all the carpentry work – cutting and fitting the stakes – before beginning with applying the earth. The stakes are typically a little longer than the panel size so that they can be inserted at a slight angle and wedged firmly into place. In the past, these were lengths of riven oak (logs or branches cleaved into strips), but nowadays one can buy stakes sawn to size. For longer lengths, the cross section can be more substantial, e.g. 40 × 60 mm when longer than 60 cm. For shorter stakes 25 × 50 mm is sufficient. For very closely spaced stakes, as seen for example in Normandy, thin battens, twigs, rods or thin split wood can be used. The ends of the stakes are worked in different ways: When fitted into triangular notches, the ends are typically trimmed to a point using a sharp axe. If the batten thickness matches that of a rectangular notch milled into the timber structure, the ends of the stakes need no further treatment. For better preservation and a better bond, the stakes can be dipped in clay slip prior to insertion.

Fig. 150 Stakes with tongues of straw-clay (see fig. 151b), historical application [Reuter 1922|

102 Light Earth Building

422-01

a) a)Stakes Stakung

c) reels c)Earth Wickelstaken

b) S  Staken takes with b) mit tongues Strohlehmzungen of straw-clay

a)

b)

c)

Fig. 151 Stakes

423

Earth reels

For walls made of earth reels, the stakes in the wall are taken out panel for panel, wrapped in light earth material to form a baton-like “reel” and then, after being allowed to dry slightly but while still moist, are reinserted working from bottom to top. The making of earth reels is described in detail in chapter 432.

Wet construction  103 

4

424-01

6

enge a)a)tightlyLattung spaced laths

Lattung b)b)laths Notch Nut

angenagelte Nailed Leiste batten

10—30

Supporting stud Hilfsstütze

c) widely-spaced c) weite Lattung laths

e) single-leaf einfache e) Lattung d) laths d) zig-zag Zickzack-Lattung

f)f) double doppelte leafLattung st == 40cm 40 cm UU == 0,22 W/m²K 0.22 W/m²K Qs 290kJ/m²K kJ/m²K Q ==290

Fig. 152 Lathwork

424 Laths The manual application of earth material on a backing of regularly-spaced laths is also a common historical method, for example in Normandy. The principle is much simpler than with wattle: sawn laths (or riven wood or rods) are fixed horizontally to the vertical supports along the entire length of the wall and covered with straw-clay or light earth. Depending on the function of the adjacent rooms, the laths are applied to one or both

104 Light Earth Building

Fig. 153 Saddle-like application of straw-clay onto a continuous backing of laths

Fig. 154 Prepared stakes in a closely-spaced half-timbered structure in Normandy

Fig. 155 Continuous laths on the internal face of a wall (Normandy)

Fig. 156 Continuous laths on the external face of a wall (see project 27)

Wet construction  105 

Fig. 157 Wrapping from within of continuous laths on the external face against an external shuttering board set back from the laths with distancing blocks (see project 27) Fig. 158 Application from within against an external shuttering board Fig. 159 Wrapping light earth onto laths

sides of the wall, about a hand width apart. As a rule of thumb, the vertical lath spacing corresponds roughly to the width of the wall. The straw-clay is placed, as described above, saddle-like over the laths. The cavity between the two faces of lathwork on either side contributes to the wall’s thermal insulation. If better insulation is required, the cavity can be filled with a poured or blown (capillary-conductive) insulation. The wall thickness can be designed accordingly.

425

Manual application onto lathwork

A lathwork of thin laths (approx. 12 × 24 mm) is fixed at 8 cm spacings (12 laths/m²) to a supporting timber construction. A malleable, heavy straw light earth mix (approx. 1,000 kg/m³) is then hooked over the laths in saddle-like rows and wound around the laths in an S-shape. For very thin partitioning walls, the application thickness can be as thin as 35 mm. The surface of the front face (application side) is then smoothed flat. This is most easily achieved by temporarily attaching 12 mm thick vertical laths as guides

106 Light Earth Building

Fig. 160 Manual application onto lathwork, wall thickness 4 cm

Fig. 161 Manual application of straw light earth

smoothed with a float

for a plaster levelling board (fig. 160). If the reverse side should also be flat, temporary formwork can be applied to the reverse side mounted on distancing blocks. The surface is then given a smoothing coat of earth mortar or alternatively a thin coat of lime plaster. For the latter, the surface of the still fresh earth should be roughened with a stiff brush or when dry scored with a plasterer’s scratch nail.

430 Floors and ceilings Filling the panels between timber joist floors with light earth adds thermal mass and improves sound insulation and fire resistance. The undersides of earth material surfaces can serve directly as a plaster base or are themselves smoothed flat and subsequently painted. The underside of a floor with earth infill can also be planed boards or a permanent formwork that is then plastered. For timber joist floors with stakes or lathwork, a malleable mass of light earth or straw clay is used. Permanent formwork is required to retain loose earth fill material and other granular aggregates, and for heavier earth masses. Floor constructions should be made as heavy as possible to improve a building’s thermal mass and sound insulation. Sticky, heavy light earth masses represent an easy way of achieving this. If, however, the ceiling needs to be thermally insulating, for example between a living room and non-insulated roofspace, the 10–15 cm of light earth between the joists is not sufficient and an additional layer of loose insulation material should be applied on top (see fig. 311).

Wet construction  107 

431-01

Brettschalung a)a)Planking

durchgehendes   b)b)Continuous laths Spalier

c) c) Planks between joists bearing battens Brett-Einschub aufon Traglatten

d)d)Laths between joists on bearing battens Lattung auf Traglatten

Einschub in Nuten e) e) Planking inserted into notches

Lattung in Nuten f)f)Laths inserted into notches

Lattung g) g) Laths restingaufgelegt on joists

Stakung in Dreikantnuten h)h)Stakes wedged into triangular notches

Fig. 162 Alternative methods of fixing a supporting floor structure to the joists

108 Light Earth Building

Fig. 163 Prepared stakes in a timber joist floor

431

Fig. 164 Timber frame construction including inserted intermediate

floor

Preparation of the timber construction

The dimensioning of loadbearing joists must fulfil structural and fire safety requirements. For some kinds of floors, edge-sawn or rough-edged wood is sufficient. Light earth is then either filled onto timber panelling or wrapped around stakes that either lie on top of the joists or span between them. The panels or stakes between the joists are either inserted into notches cut into the sides of the joist or rest on battens nailed to the sides of the joists. The stakes sit more securely if trimmed to a point at their ends and wedged into a triangular slot. The stakes are typically a fraction longer than the joist spacing so that they can be wedged in firmly at a slight angle, but not long enough to force the joists apart. Stakes or boards can also be slotted directly into the notch if the width of the stake matches that of the notch, and the notch has a rectangular profile (fig. 162 e + f). Chamfered or profiled boards left exposed on the underside should be lined with a trickle protection layer to prevent fill material trickling through. The joists are prepared on the building site prior to construction. The cutting and insertion of the stakes, or of the timber panelling, follows after the structure has been erected but before earth building works begin. This obviates the need for temporary safety provisions on the building site (see fig. 163 and 164). To improve the adhesion of the light earth mixture, the stakes can either be dipped in clay slip prior to insertion or brushed or sprayed after insertion. This also serves to preserve the wood. The following timber joist floor constructions are divided into different work methods: −− earth reel floors −− compacted earth floors on sliding formwork −− floor infill on permanent formwork −− floor infill on supporting lathwork The construction of the sub-floor and floor surfacing is not dealt with here (see chapter 660).

Wet construction  109 

Ganze Wickeldecke Full-height earth reel floor

8

cm

8

cm

432-01

Halbe Wickeldecke Half-height earth reel floor

Fig. 165 Earth reel floors

432-02 Fig. 166 Manufacture and insertion of earth reels

Prepared stakes Deckenfeld ausgestakt

Insertion of Einschieben reels Surface with Abgleichlevelling mit Strohstraw-clay or chopped oder Häcksellehm fibre-clay

Earth reel with long-stem Wickel aus straw Langstroh

Earth reel Wickel aus with light Ballenstroh earth from bale straw Reel rolling table Wickeltisch

110 Light Earth Building

Fig. 167 Lime plastered underside of a “Kölner Decke” or Cologne ceiling (Lehmbau Breidenbach)

432

Earth reel floors

Stakes made of uncleft wood (3 to 5 cm diameter), of riven hardwood or strong battens (see chapter 422) are wrapped with straw-clay and inserted between the floor joists. Due to the high proportion of straw in this traditional method, it counts as a light earth technique: the dry bulk density and coefficient of thermal conductivity correspond to those of light earth (DIN 4108 1969). Although the qualities of this wonderful historical technique are widely lauded in the available literature, its fabrication is often assumed as being common knowledge or else is passed over in favour of the simpler timber joist floor with intermediate floor. A full earth reel floor fills the entire height of the timber joists and is therefore comparatively heavy, acting as noise insulation, thermal mass, fire protection and plaster base in one. The reels are arranged to be flush with the bottom face of the joists so that the space above can be filled with a light earth or straw-clay mass or with naturally-moist earth fill material or – after drying – annealed sand. While the underside of the joists can be left exposed, it is more common to apply a plaster base to their undersides and to plaster the surface of the ceiling (offering added fire protection and a smooth unbroken ceiling). The half earth reel floor fills only part of the height of the floor and is therefore lighter. The earth reels are arranged to be flush with the upper face of the joists with the lower parts of the joists visible on the underside. After insertion of the earth reels but before dry, the underside of the earth reels can be smoothed flat. Manufacture of earth reels with long-stem straw With this method, one takes as much long-stem straw as one can in one hand and dips it in a thin solution of clay slip, making sure the bundle is fully wetted, before pulling it out of the vat in a twisting motion. This “rope” of straw soaked in clay is laid diagonally on the table and coated with a 2 cm thick layer of earth. The stake, likewise dipped in clay slip, is placed parallel to the table edge and, starting at one end, wrapped with the straw in a spiral motion to form a 10 to 15 cm thick roll. Any irregularities can be smoothed out with straw clay. The earth reel is then ready for insertion into the building [Miller et al. 1947].

Wet construction  111 

Fig. 168 and 169 Earth reel with coarse hay and slip: a portion of hay is spread on the table and coated with slip. A pouring container is fashioned to define the required quantity of slip. The resulting light earth mix is rolled onto the riven wood stakes.

Fig. 170 Reels ready for insertion

Fig. 171 Reels inserted between joists

Manufacture of earth reels with light earth from bale straw This somewhat simpler variant employs shorter lengths of straw , e.g. directly from a bale. A heavy mix of light earth mass is prepared as usual by dipping or spraying and then after prolonged tempering spread out like a 2 to 4 cm thick layer of “dough” on the table. The stake is laid on the mass and wrapped in the earth mass. Manufacture of earth reels with coarse hay and slurry In this even simpler and clean approach (common in Normandy, for example), the loose hay is spread out on a table and then coated with a layer of thick clay slip. The resulting mass is then wrapped around the stake (see figs. 168 and 169). Installation of earth reels The timber joist floor is fitted with stakes at around 10 to 15 cm spacings – approximately the width of an earth reel (figs. 163 and 171). Working from beneath on low scaffolding so that the ceiling is at head height, one begins by shifting back the stakes at one end to leave an approximately 1 m long work space. In order not to mix up the stakes, they are removed one by one, wrapped into a reel and then reinserted and pushed back into

112 Light Earth Building

place. While one reel is being inserted, the next can be wrapped. The reels are pressed firmly up against one another and peaks and troughs in the underside then smoothed flat with straw-clay or chopped straw-clay and a levelling board. If the underside is to be plastered, one can leave the surface flat but rough. Once five or six reels have been put into place, the space above them can be filled up to the desired height with straw-clay and levelled off flush with the top face of the joists (see fig. 446).

433

Compacted earth floors on sliding formwork

Much like with compacting earth in a wall construction, the earth mass is compacted from one side into a cavity formed by sliding formwork. After removal, the formwork leaves a smooth, plasterable underside. Depending on whether the lower formwork is attached beneath or between the timber joists, the floor panels may be partially or completed filled with earth mass and the undersides of the joists left exposed or plastered over. If the stakes are laid on side battens or the tops of the joists, any kind of wood can be used, e.g. round rods, battens, off-cuts, riven wood. One should plan with around 8 stakes for 1 metre. The formwork should be mounted no more than 5 cm behind it so that the mass hanging on the stakes is not excessive. The top surface of the formwork should be smoothly planed or made of formwork plywood. If the formwork is placed between the joists, the panels should be slightly thinner than the space between the joists to prevent it from jamming. If the joist spacings vary, a smaller width is used with filler pieces for the wider spacings. If the underside of the floor fill material is to be flush with the joists, wider formwork panels can be used and pressed up against the underside of the joists with extendable ceiling struts. The formwork is best fixed to the ceiling struts (fig. 173). The formwork can also be laid on temporary bearing battens between the timber joists. To ensure the formwork can be removed and shifted along the joists, additional removable runners are placed between the battens and formwork (fig. 174). To insert and compact the earth material from above, one kneels on a shuttering board placed across the tops of the joists that covers the panel from above. The stiff sticky light earth mass – ideally made of 15 to 20 cm long, soft straw – is thrown into the pre-wetted formwork and pressed and compacted into the cavity between the formwork below and the board above, taking special care to push it into the corners and beneath and around the stakes (fig. 173). The straw clay mix can be attached most effectively to the stakes by wrapping them with light earth mix pressed flat. After five to six fillings, the formwork is released and shifted forward by tugging sharply on a handle screwed to the formwork. The freshly compacted ceiling may not be trodden on until completely dry – although it dries fairly quickly as it is exposed above and below. If sufficient formwork is available, the entire underside of the floor can be equipped with shuttering and supports, much like when pouring a concrete ceiling. Compaction can then progress more quickly because it is no longer necessary to laboriously reposition the lower set of formwork. The floor should be allowed to dry a while before removing the formwork (fig. 176).

Wet construction  113 

433-01

Full-height compacted Ganze Stampfdecke floor infill

Half-height compacted Halbe Stampfdecke floor infill

Fig. 172 Compacted floor applied on sliding formwork

433-02 Fig. 173 Compacted floor: insertion onto a shuttering board pressed from below against the ceiling

Sprieß Strut

Variant: Wrapping stakes Variante: with light earthder Staken Umschlingen mit Leichtlehm

114 Light Earth Building

Fig. 174 Compacted floor: the mass is compacted onto a shuttering board laid on temporary battens fixed to the sides of the joists so that it can be slid along between the joists

Fig. 175 Compacted floor: underside (see project 1)

433-05 Fig. 176 Compacted floor: insertion onto full-surface shuttering

Wet construction  115 

434-01

a) Schalungresting auf den a) Planking on Balken joists

Spundbohlen Tongue and groove boarding

Bohlen mit Deckleisten Boarding with cover strips

b) Schalungbetween zwischen den Balken b) Planking joists

Spundbretter Tongue and groove boarding

Stülpschalung Board and batten boarding

c) Fehlboden und Verkleidung c) Intermediate flooruntere and ceiling cladding

Schwarten Edge bark lumber

ungesäumteboards Bretter Untrimmed

Fig. 177 Floor infill on lost formwork

434

Floor infill on permanent formwork

Formwork panels are either nailed to the floor joists, laid between them on battens or slotted into notches in the timber joists to create an intermediate floor. This floor type is simple to make but requires more wood. All kinds of light earth are suitable as a fill material, including woodchip light earth or mineral light earth. Where sound insulation or thermal mass needs to be particularly good, the floor can also be filled with straw-clay or fibre-clay, with naturally-moist or dry earth fill material, or even laid with dry earth bricks. When using dry earth materials, a vapour permeable building paper should be laid on the formwork to prevent dust trickling through. Alternatively – and also suitable for wet fill material – a 2 cm thick coating of straw-clay or fibre-clay can be applied and then left to dry. The undersides of timber panel floors can be left exposed or alternatively concealed by a second lower ceiling, which may serve a particular purpose, such as fire safety. If concealed, the floor can be made of waney-edged planks or untrimmed boards. Exposed ceilings can also be fire-resistant if sufficiently thick and with fire-resistant joins (see chapter 833). Wood is not the only lost formwork that can be used: 5 cm thick reed boards or wood-wool building board are alternatives that also act as a plaster base for a ceiling plaster.

116 Light Earth Building

Fig. 178 Light earth floor infill on lost formwork showing both the floor surface and the ceiling (see project 2)

435

Floor infill on supporting stakes

Lath floor A viscous mass of light earth or straw-clay is filled from above and pressed between the 3 to 5 cm wide spaces between a pre-mounted lathwork, so that about 5 to 10 cm long tongues of light earth mass hang through, which are then pressed against the ceiling from below with a narrow float and smoothed flat with an earth mass mixed with chaff or chopped straw. A fine, fibrous light earth made with a soft straw such as oat straw or coarse hay is suitable. If the lathwork extends the entire width of the room, passing over the joists, roundwood can be used to save money, either whole or split down the middle (3 to 6 cm thick), placed in alternating directions (base to top). Alternatively thicker off-cut material (tree limbs etc.) can be used (so-called light earth ‘lined’ floor, or light earth rod floors). Battens placed between floor joists must be wedged firmly into notches in the joists to prevent them slipping while applying and pressing through the earth mass. Plaster lath ceiling The plaster lath ceiling has thinner 2 to 2½ cm thick battens at spacings of around just 2 cm which are nailed to the underside of the timber joists [Fauth 1946, 1948, p. 71]. Light earth material can be applied in a thinner layer and pressed through the laths to create a flat ceiling surface and a larger floor cavity, which can, for example, be filled with insulation material. If the joist spacings are narrow, the plaster lath is sometimes applied to the top surface of the joists.

Wet construction  117 

435-01

„Lehmstangendecke“ “Lehmstangendecke” „Lehmstreckdecke“ “Lehmstreckdecke” Roundwood to the Stangen aufnailed den Balken genagelt top of the joists

Stakes wedged between Staken zwischen den Balken the joists geklemmt

5−10 cm

3−5 cm Construction Herstellung principle

3−6 cm

Raum for für ceiling Cavity Deckenfill material or schüttung insulation

2 cm

Spalierputzdecke Plaster lath floor

Battensunter screwed Latten die to underside of joists Balken geschraubt

2 cm Fig. 179 Floor infill on supporting framework Fig. 180 Underside of lath ceiling with combed face providing a mechanical key for a subsequent layer of plaster Fig. 181 Underside of lath ceiling

118 Light Earth Building

Plastered stake ceiling A reed plaster lath is stapled to the underside of a supporting timber construction of laths or stakes and serves as lost formwork for filling the floor construction with a light earth material. After the earth mass has dried the underside of the reed plaster lath can be plastered.

436

Suspended lath ceilings

As described above for the walls (see chapter 425), malleable straw light earth can wrapped in an S-shape around laths fastened to the timber joists, and then smoothed to a flat surface from below (fig. 181).

440 Roof insulation Compared with typical insulation materials, the use of light earth for roof insulation provides better sound insulation and thermal mass due to its higher weight per unit area, and is therefore an effective means of reducing overheating in summer. The homogenous layer of material can also serve directly as a base for plastering. While it provides a good measure of thermal insulation, additional insulation is required to achieve the U-values required today for permanently heated rooms. The thickness of the light earth layer can be between 5 and 20 cm thick and, depending on the application method, can also be made with very lightweight mixtures (300–400 kg/m³) which are only lightly compacted to ensure better material porosity. The adhesion of the clay prevents the thermal insulating mass from settling. The surface of a light earth roof insulation layer should be sealed with a layer of earth on the outer face and a layer of plaster on the inside to ensure insulation across the entire cross section and to draughtproof the roofspace. The weight of the mass of material must be taken into account in the structural dimensioning of the rafters. Any kind of roof covering is suitable as long as it is ventilated. A second water run-off layer is recommended to prevent moisture infiltration from leaks or driven snow. As with joist floors, there are different methods for inserting light earth into roofspaces: −− light earth reels −− behind sliding formwork −− behind permanent formwork −− on lathwork If the roof has already been covered, one must work from within – and can work un­­ affected by weather. In some cases, and particularly with shallow roof inclines, it can be more practical to insert the material from above, for example using a crane or inclined conveyor, and to apply the roof covering afterwards. Tarps or foil can be used in the meantime to protect the roof from the rain. Light earth typically dries quickly in roof situations, provided that one does not use permanent formwork on both sides.

Wet construction  119 

Additional insulation layers in the form of boards can serve as permanent formwork. Alternatively dry insulation material, such as cellulose, can be blown into the cavity once the earth has dried. If used, insulation boards should be vapour permeable and capillary conductive. Reed mat insulation or wood-wool lightweight building boards are two suitable materials. See figure 311 for details on the U-values of roof insulation with light earth.

441

Light earth reels

Light earth reels are easily inserted from beneath because the reels are of a manage­ able size. There is also no need for formwork. The ventilation of the roof cladding (3 to 5 cm) is easily achieved by dimensioning the reels accordingly. Because the reels are made of a comparatively heavy light earth mix (800 to 1,200 kg/m³), thinner reels of approximately 10 cm diameter can be made and inserted flush with the underside of the rafters. The resulting cavity can then be filled with a loosely inserted lightweight earth mix (300 to 400 kg/m³) or after drying with blown-in cellulose insulation. The holes made to blow in the insulation material can be sealed afterwards with straw-clay.

442

Compaction behind sliding formwork

As with the corresponding floor construction, light earth is inserted including stakes behind a sliding formwork, to produce a smooth surface ready for plastering. Shuttering panels are either screwed in place or temporarily supported from beneath with struts. A simpler method, as with the wall-high yoke (see fig. 121 C), is to use squared timbers to clamp the shuttering boards against the rafters. If the roof has already been covered, the necessary air cavity for ventilating the roof covering can be achieved by inserting an insulation panel as lost formwork.

443

Infill behind permanent formwork

The earth mix is filled behind a formwork made of wood or plasterable reed matting and compacted. The formwork remains in place and is not removed. For steeper roof inclines, the formwork can be screwed from beneath against the rafters. Formwork that is either inserted between the rafters and fixed laterally or is fixed above the rafters is better if loads need to be sustained, as is the case with a flat roof. If working from beneath in the roof space, the formwork should be fixed or inserted section by section as work progresses. Screwed on formwork is best filled from above in a single operation.

444

Infill on lathwork

The earth mix is pressed into the 3 to 5 cm wide spaces between a series of parallel battens, rods or split rods (of 3 to 5 cm diameter), and smoothed on the underside.

120 Light Earth Building

441-01

Light earth fill Leichtlehmmaterial füllung

Insulation fill DämmstoffFüllung material

a)

b)

c)

Fig. 182 Light earth reels (roof insulation)

443-01 Fig. 183 Roof infill behind lost formwork (roof insulation)

1

3

2 1

2

a) Filling Füllung vonwithin innen a) from

Füllung oben b)b)Filling fromvon outside

Wet construction  121 

444-01

1

2

a)a)Filling from below against board Füllung von unten gegeninsulation Dämmplatte

2 3

1

b) from above continuous set of b)F illing Füllung von obenonto auf adurchgehendes Spalier, laths plus Einblasdämmung cavity insulation

Fig. 184 Roof infill applied onto laths (roof insulation)

The lathwork is nailed or screwed, much like lost formwork, prior to filling with light earth, or else inserted in sections as work progresses, whether working from the bottom up or top down. As with the corresponding floor construction (see chapter 435), a more tightly-spaced lathwork of thin battens can be mounted, onto which heavy light earth or straw clay is applied and smoothed, either from above or below. The thin layer (approx. 5 cm) leaves enough space for additional insulation, for example cellulose insulation blown into a cavity behind the lathwork and an external insulation board (e.g. bituminous softwood panel) or sheathing.

445

Inner lining on lathwork

As described in chapter 425 under walls (manual application onto lathwork), a mal­le­ able straw light earth mix is hooked over the laths fixed to the underside of the rafters in saddle-like rows and wound around the laths in an S-shape. The underside is then smoothed flat. Ventilation slots are left to allow the cavity behind to dry out more quickly. After drying the slots can be sealed and the cavity filled with blow-in cellulose insulation material (fig. 187). Alternatively, as with internal wall insulation (see chapter 454), the space between the rafters is filled with insulation (e.g. insulation made of natural fibres) and the light earth mix then applied at a thickness of 25 to 30 mm and pressed between the laths and smoothed.

122 Light Earth Building

Fig. 185 Roof, ceiling and wall cladding using straw light earth applied onto a backing of lathwork

Fig. 186 Light earth on lathwork (roof insulation)

3

1

4 cm

25

 cm

2

1 Plaster laths 24 × 12 mm 2 Straw light earth, manually applied 3 Cavity insulation Fig. 187 Inner wall lining, 4 cm thick, with blow-in cavity insulation

Wet construction  123 

450 Light earth in building restoration Light earth – alongside straw-clay and fibre-clay – is an ideal material for renovating and converting half-timbered buildings with earth infill. Old panel infill material can be retained and repaired with a similar material, and where this is not possible, the infill of walls, floors and roof inclines can be renewed as described above.

451

Panel infill with straw-clay

The advantage of using straw-clay over masonry as a panel infill material is its better connection to the timber structure and greater elasticity. Bricks have to be cut to size while straw-clay adapts to fit.The seamless connection between the timber members and the panel infill and with it the straw or wood in the earth mix is exceptionally durable (see chapter 614). A properly executed panel infill fits the panel tightly and any moisture that does infiltrate the small gap at their junction is quickly and reliably absorbed by the fill material due to its good capillary conduction. Masonry on the other hand – especially with artificial bricks or hard mortars – is less able to accommodate movement in the structure, and cracks inevitably form through which water can enter and trickle down through the mortise holes. Filling the gap with an elastic sealer is problematic as it is never truly durable and at some point water gets in that can’t get out. Old half-timbered houses can survive many years of neglect, only to rot after a few years of misguided repairs. The advantage of earth infill is its ability to protect the building substance by keeping it dry. Intact straw-clay infill panels can and should always be retained, obviating the need for demolition, removal, refuse fees and renewal of the panel. Holes can be easily repaired with straw-clay or fibre-clay. One can try to repair crumbled material by injecting water to soften it and working it with a suitably pointed tool. The earth material for repairs should have similar characteristics to the existing substrate. Where external surfaces are to be given a thin layer of lime plaster the entire surface should be wetted, after completing any necessary repairs, and then a fibrous earth mixed worked into the surface with a float. The resulting flat surface is then roughened or scored while still wet with a suitable tool, traditionally a wooden comb or scratcher (fig. 193). The scratch pattern need not be pretty, just sufficient to make the fibres of the substrate stick out as a mechanical key for the lime plaster. In Normandy, the surface is typically scratched crosswise with a manure fork (see chapter 642). Loose stakes can be secured at their ends without removing the entire panel, by screwing or inserting oak nails into pre-bored diagonal holes. Stakes between floor joists may be able to be secured and retained by adding a further loadbearing batten.

124 Light Earth Building

Fig. 188 Renovation and conversion of a house from the Gothic period (1289) in Limburg an der Lahn (Römer 2–6). External and internal wall infill made of straw-clay on wattle, floors filled with straw-clay mass. New internal wall lining with straw light earth and lime plaster (architect: Götting-Kramm-Neuhäuser, construction: Lehmbau Breidenbach, 1990)

Wet construction  125 

Fig. 189 New panel infill with straw-clay on wattle backing

Fig. 190 and 191 Intact parts of infill panels are retained and supplemented with new material.

Examples from Hessia, Germany (see project 12) and Normandy, France Fig. 192 Application of the final topcoat of fibre-clay using a Japanese trowel Fig. 193 Comb used to create a mechanical key for a subsequent plaster coat

126 Light Earth Building

Fig. 194 Lime fine-finish render, flush with exposed timber members (see project 11)

Panel material that is removed can be recycled for use elsewhere, for example as fill material for weighting floors. Any material with visible salt efflorescence, or from the walls of animal housings, should not be used and any layers of soot soiling removed. After freeing the earth material from any remaining plaster and pieces of wood, it can then be soaked in water or repeatedly watered at intervals until it has soaked up enough water to become workable. Straw can be added to control the mixture. Wooden stakes are often still in good condition and can also be re-used. New or replacement panel infill with straw-clay should try and replicate the con­struction method used in the rest of the building. Given the sometimes considerable differences in the quality and kind of construction, often within the same building, it should in most cases be possible to use a different method of better quality than the original. Wattle and daub need only be applied to the outer face of the structure so that an inner insulating layer can be as thick as possible (see figs. 200 and 201c). See chapter 420 (manual application) for further information on the composition and use of straw-clay.

452

Panel infill with light earth

If better thermal insulation is required, new panels can be given an infill of light earth, inserted and compacted in sliding formwork as described above. External walls should be about 25 to 30 cm thick. For wet insertion, the inner slide rails for the shuttering panels are fixed a corresponding distance into the panel (see figs. 116 B and 201).

Wet construction  127 

All timber elements are first cleaned and then coated with clay slip to improve the adhesion of the light earth mass. The external face of the panel can be set back to accommodate the thickness of a facing plaster by placing a suitably thick panel inside the formwork (see chapter 621). Because compaction can be laborious due to the many horizontal timber members of the structure, earth masonry infill (see chapter 542) or wattle and daub infill (see above) are more commonly used as the external face with additional wall lining on the inner face for insulation if required.

453 Insulating wall lining of external walls If the panel infill of a timber-frame construction is in good condition but its thermal insulation capacity needs to be improved – for example when made of straw-clay or bricks – an internal wall lining of light earth can be applied. The same principle can also be applied to all kinds of masonry walls with insufficient thermal insulation. Construction Any remaining paint, wallpaper and loose layers of plaster are removed from the internal face of external walls and the wall brushed down and then painted with a coating of clay slip. Intact layers of plasters can be left as is, and historically-valuable plasters should

Fig. 195 New panel infill with light earth

Fig. 196 Slide rails determine the new wall thickness Fig. 197 Formwork

128 Light Earth Building

be retained by applying a layer of clay slip or clay plaster. The thickness of the wall lining is defined by the distance of the timber studs or vertical wood batten construction from the wall. Fixed securely so that they cannot come away from the wall, these act as slide rails for the sliding formwork, and retaining surface for the light earth mix. To improve their hold, short horizontal connecting pieces are compacted in the wall infill behind the vertical battens. The shuttering boards are screwed or clamped (fig. 199) to the vertical construction following the principle of one-sided sliding formwork (figs. 134 and 201). If formwork without slide rails is used, the resulting surface of the wall lining is continuous, thereby obviating the need for a plaster base or mesh to bridge the vertical timber elements. Internal wall linings have only one exposed face and dry comparatively slowly. For this reason, they should not be thicker than 15 cm. Thicker layers should be realised using dry light earth masonry blocks or panels to avoid drying problems (see chapter 543). Building physics While an internal wall lining made of light earth cannot fulfil modern thermal insulation requirements, it does improve thermal insulation, provide adequate thermal retention, and raise comfort levels through the wall’s warmer surface temperature. In certain circumstances, existing walls may be exempt from these stipulations, for example when insulation measures would be detrimental to the building construction. This is often the case with

Fig. 198 Prepared construction for an internal wall lining Fig. 199 Compaction of internal wall lining (see project 1)

Fig. 200 Woodchip light earth

internal wall lining with reed plaster lath as lost formwork and strawclay daub on the external face of wattle (construction: Lehmbau Breidenbach)

Wet construction  129 

453-01

a) a) EVorhandene xisting straw-clay panel Strohlehmausfachung Internal wall lining with slide rails Innenschaleshuttering mit Gleitlehre Screw-fixed boards Schalung aufgeschraubt a) a) Vorhandene Strohlehmausfachung Innenschale mit Gleitlehre Schalung aufgeschraubt a) Distanzrohr

Distancing piece Distanzrohr

b) Strohlehmausfachung b) EVorhandene xisting straw-clay panel ohne without Gleitlehre IInnenschale nternal wall lining slide rails Schalung über Shuttering fixedDistanzrohr with distancing pieces geschraubt b) Vorhandene Strohlehmausfachung Innenschale ohne Gleitlehre Schalung über Distanzrohr geschraubt

30 c) N ew straw-clay application from c)   euer Strohlehmauftrag nur c) Neuer Strohlehmauftrag nur von von außen outside only Internal wall lining aussen Innenreed Schilfrohrgewebe als with plaster lath as lost Schilfrohrgewebe als 30 verlorene verlorene Schalung Schalung formwork

b)

b)

c) Neuer Strohlehmauftrag nur von aussen Innen Schilfrohrgewebe als verlorene Schalung

Fig. 201 Internal wall lining for renovation of a half-timbered structure Fig. 202 Woodchip light earth in-

ternal wall lining compacted behind reed plaster lath as lost formwork Fig. 203 Woodchip light earth in-

ternal wall lining compacted behind sliding formwork

130 Light Earth Building

1 Existing wall 25 cm

2 Insulation board mounted between screwed-on battens

2.5 cm 1 2 3

3 Straw light earth, manually applied onto plaster lath, 24 × 12 mm

Fig. 204 Manual application smoothed with a float. The

Fig. 205 Internal insulation, clad with

thickness of the vertical lath determines the thickness of the plaster. Closing the gaps with the same material

straw light earth applied manually

historical timber-frame and half-timbered constructions. Light earth wall linings are one of the few problem-free ways of insulating the inner surface of external walls, and have been used successfully in the renovation of countless half-timbered structures. Moisture damage through the occurrence of condensation water within the wall structure is not a concern with this kind of “internal insulation”. According to DIN 4108-3 2014, the calculation of the dew point is not necessary as long as the wall consists of normal capillary conductive building materials such as artificial stone, brick or earth. Care must be taken with less capillary conductive building materials, for example clinker brick, and a dew point calculation is then recommended. Internal vapour barriers should be avoided, as should air cavities between the earth wall lining and the external wall, as this interrupts the moisture transport and prevents the wall from effectively dissipating moisture (see chapter 825).

454

Internal insulation applied to lathwork

With this construction, a timber supporting construction is mounted on the internal face of an external wall between which a capillary conductive fibrous insulation material can be inserted. Laths are then fixed to these supports at regular spacings as described earlier under walls and roofs (see chapters 425 and 445). A malleable straw light earth mass is prepared and either thrown or daubed onto the lath and smoothed with a float to form a 25 to 30 mm thick layer. Vertical plaster laths fixed temporarily to the cross battens can be used to ensure the surface is flat and plumb (see figs. 204 and 205).

460 Spray application approaches Plastering machines can be used to mix earth and light earth mixes with fine fibres, and then to pump and finally spray-apply the mix onto wall surfaces. Suitable backings or plaster bases include tightly spaced battens or laths, solid wall surfaces such as

Wet construction  131 

Fig. 206 Spray application of

chopped460-01 straw and earth mix onto lathwork, Picardie (Lahure)

Fig. 207 Mixing of chopped straw earth in a compulsory mixer

(Allonne Brickworks, Picardie)

a) A vonfrom innen a)  Auftrag pplication within gegen Schilfrohrplatten against reed insulation board

b) A vonfrom innen b)  Auftrag pplication within gegen gedämmte against insulated timber Holzständerwand stud wall construction

a)a)

c)  xposed half-timbered wall, c) E Sichtfachwerk Auftrag vonfrom außen gegenagainst application outside Innendämmplatten internal insulation board Fig. 208 Spray application of earth mix onto an external wall

masonry (existing buildings) or lightweight building boards which serve as lost formwork. The material can be applied up to a thickness of 5 cm in one go. Further applications are possible once the base layer has been allowed to dry for about a week. Special techniques have been pioneered [Kortlepel/Kraus 1994] that allow the spray application of light earth with aggregates such as sand, sawdust and finely-chopped straw with bulk densities of between 800 and 1,800 kg/m³.

132 Light Earth Building

500 Dry construction A large number of manufacturers now offer a variety of ready-made products for dry construction ranging from bricks and blocks of different sizes and formats made of earth and light earth to large-format panels and building boards. Ready-mixed dry masonry and plaster mortars are also available that make it easier and faster to employ earth building materials on the building site. One can also produce one’s own bricks and panels using very simple means: while the process requires more preparation time for making and drying the blocks compared with wet construction methods, the advantages of dry construction are compelling: −− minimal moisture is introduced into the building and work can take place year-round −− manufacturing conditions can be optimised −− simple and clean to install by a bricklayer without special skills or knowledge −− no need for formwork and supporting construction, and larger distances between timber studs are possible −− quality control is easier to achieve Offcut earth brick material can be recycled for use as fill mass, and sometimes also for mortar or plaster if the aggregate is fine enough. Even when wet methods are used for light earth construction in the external walls, it can still be advantageous to complete internal walls using light earth masonry or dry lining boards. The production of one’s own materials can take place away from the site and can begin before commencement of construction on site, for example in the year before, to reduce the duration of construction works.

510 Light earth bricks and blocks Light earth bricks are suitable for internal walls and weighted floors, for panel infill and thermally insulating external walls – with or without additional insulation depending on the bulk density of the bricks. The advantage of light earth bricks over heavier bricks is not only their lighter weight but also their more balanced thermal properties and surface warmth. Bricks made with a fibrous aggregate are more resistant to chipping, less susceptible to moisture and frost, and swell minimally when absorbing moisture. In most cases they fall within Application Class I as described in the Lehmbau Regeln (see fig. 321), i.e. they are suitable for use as panel infill and (when rendered) for external walls exposed to weather. The low weight of light earth makes it possible to make larger block formats. However, the use of typical brick sizes, which in Germany are based on defined fractions of a metre, makes it possible to plan and calculate with conventional construction dimensions, methods and quantities. The minimum compressive strength of light earth bricks is on average about 0.1 N/mm². The actual self-load of a storey-high wall of light earth masonry at the base is between three and seven times less. The compressive strength increases with the bulk density of the brick.

Dry construction  133 

Fig. 209 Light earth block

Fig. 210 Light earth blocks

(from the Finnish manufacturer Timo Lehtonen, Kumila, see project 13)

511

Brick-format products

Bricks are available in a range of different easy-to-handle formats (NF, 2DF, 3DF and 4DF where NF = normal format and DF = thin format, see fig. 211) made with fine, mixed aggregates and bulk densities of between 400 and 1,200 kg/m³. Commercially available light earth bricks, when manufactured in small-scale industrial production, are comparable in cost or only slightly more expensive than conventional bricks, but are much more ecological in their manufacture and easier in their handling. As energy costs increase in future, their cost of manufacture is likely to fall in comparison to fired bricks because earth products require less energy input to dry. Further rationalisation in the still comparatively young market will lead to more optimised manufacturing processes, and increasing supply and competition is likely to bring down costs, making the use of earth building products more affordable and more widespread.

134 Light Earth Building

4D F

24

17

2D F

11.5

Formate brick nach sizes DIN 105: German (DIN 105) (Normalformat) 24 × 11,5 × 7,1 cm NF (Normal Format)L/B/H l/b/h == 24 × 11.5 × 7.1 cm (Dünnformat) L/B/H==24 × 11.5 × 5 cm 24 × 11,5 × 5 cm DF (Thin Format) l/b/h (2 × Dünnformat) L/B/H==24 × 11.5 × 11.5 cm 24 × 11,5 × 11,5 cm Format) l/b/h 2DF (2 × Thin L/B/H==24 × 17.5 × 11.5 cm 24 × 17,5 × 11,5 cm 3DF l/b/h L/B/H==24 × 24 × 11.5 cm 24 × 24 × 11,5 cm 4DF l/b/h

11

11

24

.5

24

.5

NF

7.1

.5

11.5

24

24

30

3D F

11.5 5D F

11.5

24

Fig. 211 Typical brick formats as given in DIN 105

Fig. 212 Light earth brick and block

products in NF and 2DF format (Claytec®)

Fig. 213 Hemp light earth blocks in 12DF format

(49 × 24 × 17.5 cm), 0.4 kg/dm³, hand-moulded (Benzin Brickworks)

520 Light earth panels A range of panel-shaped products can be used for large-format wall infill and for cladding and dry lining. According to the Lehmbau Regeln, earth panels, with and without reinforcement, may only be used in self-supporting floor constructions, i.e. they cannot sustain live loads.

521

Panel-format products

Earth building panel elements Earth building panel elements made of light earth or another heavier fibre-clay mixture with a thickness of 6 to 12 cm can be used for internal walls and wall linings and are either laid in mortar like large bricks or placed dry alongside one another in a suitable

Dry construction  135 

Fig. 214 Earth building board,

Fig. 215 Earth building board

Fig. 216 Fibre-clay panel and

0.7 kg/dm³, 1,250 × 625 × 25 mm (Claytec®)

made of fibre-clay, 1.4 kg/dm³, 1,000 × 625 × 25/16 mm (Conluto®)

wall-heating panel (WEM®)

supporting construction that holds them in place within the timber frame. For better handling, they are generally not large (e.g. 80 × 30 cm). Earth building dry lining boards Thin building boards made of light earth or fibre-clay are between 16 and 35 mm thick and can be used like dry lining boards to quickly clad a supporting construction, in conjunction with wall insulation, or as lost formwork for slightly wet or dry woodchip light earth. Their flat surfaces can be plastered with a fine skim coat that dries quickly. Earth building boards are generally 120 cm long and between 30 and 60 cm wide. Wall heating panels are also available with pre-mounted loops of heating register embedded within the panel (figs. 214–216).

530 Self-produced bricks and panels Light earth bricks, blocks and panels can also be made in moulds for later use with earth mortar in the building. Suitable aggregates for the light earth base include short straw fibres or woodchip, together with admixtures such as sawdust, granular additives or combinations thereof. The length of the straw should correspond to the shortest dimension of the brick. In lightweight bricks with a low earth content, the straw fibres increase the strength of the brick, making it more robust for transportation and bricklaying. The ratio of clay slip and aggregates depends on the desired properties of the resulting brick and can be derived as detailed in chapter 334.

531

Manual manufacture

Light earth for panels and large block sizes can be pressed by hand into a mould of the corresponding size. The mould typically comprises an open frame made of planed wood, shuttering board or sheet metal that is open at the top and bottom and when

136 Light Earth Building

531-01

Wooden mould Holzform

3

0.5 h

50

Hand-held Handstampfer tamper

h

1.5 h

15

b

l

Formrahmen Mould frame (nach Pollack, Richter) (after Pollack/Richter) Twin mould with Doppelform mit metal web Blechzunge Pressing table Stampftisch

Sheet metal Blechform mould

Mould Formfor fürreinforced panels or slabs bewehrte Platten

eingeschobene Inserted battens as rests Auflagerhölzer für for the ends of wooden Stakeinlagen bars reinforcement Brick compaction Stampfen auf ondem the floor Boden

Fig. 217 Manual manufacture of panels, blocks and bricks 1

Dry construction  137 

25

50

Hebelpresse Lever setup for pressing für Steine Platten bricks and und panels

Mould removal Entformen

a) M  Hochziehen ould lifts off,der Form, brick is removed Tragen auf on underlay Unterlagsbrett b) MHinunterould slides drücken der Form, downwards, Tragen auf brick is removed Einlegeboden on baseboard

Absetzen Laying brickszum outTrocknen to dry

Fig. 218 Manual manufacture of panels, blocks and bricks 2

138 Light Earth Building

90

120

24 · 74

24 · 49

24 · 24

.

24 · 36,5

531-02

200

Lever arm varies according brick Hebelarm je nach Stein- bzw. or panel size Plattenformat With a pressing force of 0.2 kp/cm² bei Pressdruck mit 0.2 kp/cm² (2 N/cm²) Muskelkraft P = 40 kp Muscle force P = 40 kp (400 N)

cm

used with straw light earth is about half the brick height higher than the brick. A loose light earth mass is filled into the mould and then compacted. The mould height = 1½ × brick height. As light earth only shrinks minimally, the mould can have the same internal ­dimensions as the resulting brick. The tamper is made of hardwood and has stops (e.g. rabbeted edges) on both sides so that the light earth can only be compressed to a defined height. The mould must be placed on a flat, firm surface during compression. If compacting on the floor, a tamper with a long handle is used. An effective work setup can be constructed on a table such that the light earth mixture can be pushed from the mixing surface into a lower lying mould. It is then evenly distributed by hand or with a small fork, pressed into the corners and then compacted with a short-handled tamper. For self-supporting, reinforced panels, the wood reinforcement is first soaked in a clay slip and then laid in the form. So that they all lie in the same plane, timber battens are first laid in the mould where the future bearing edge will be [Pollack/Richter 1952]. Hand-operated press Light earth bricks and panels are compressed with a force of 0.2 to 0.4 kp/cm² (0.02 to 0.04 MPa). That is very small compared with the forces of between 7 and 10 kp/cm² used for making compressed earth blocks with a lever-operated press such as the ­Terstaram Press® (see fig. 27). For light earth building, a press first had to be developed that is appro­priate to both the material and the larger brick and panel formats. Pollack/ Richter [Pollack/Richter 1952] show examples of brick and panel presses, but they seem too complex for small building projects. For self-builders, a lever construction of the kind shown in figure 218 is easy to make oneself (see figs. 225 to 229). By increasing the length of the lever arm, panels can also be compressed. Figures 219 to 221 show a table construction for pressing light earth bricks with a foot-operated mould ejection mechanism.

Fig. 219 Manufacture of light

earth blocks using a hand-operated press (Rheinländer)

Fig. 220 Compressing the block

Fig. 221 Releasing from the mould with a foot-operated pedal

Dry construction  139 

Fig. 222 Drying

Fig. 223 Bricklaying with light

earth mortar Fig. 224 Roughened surface to

improve plaster adhesion

Fig. 225 Table with hand-operated lever press (see project 4)

140 Light Earth Building

Fig. Fig. Fig. Fig.

226 Insertion of material into mould 227 Compression of the material with metal lid piece 228 Removal from mould 229 Transportation on base board

Fig. 230 Working and

cutting panels and bricks

Mould removal and drying Panels and large-format bricks are freed from the mould by lifting it off by its side handles in a single sudden movement. This is made easier by wetting the inner faces of the mould and ensuring they are smooth. The mould can be fabricated to taper outwards slightly towards the bottom to ease removal. Prior to compaction an underlay board is placed beneath the form with which the resulting formed brick can be carried to a place to dry (fig. 218). Smaller moulds can be slid downwards: a baseboard is first inserted into the mould and the brick compacted. The entire assembly is then shifted from the compacting or pressing table onto a surface slightly smaller than the base board. The mould can then be slid down and the brick removed. As soon as the bricks are firm enough, they should be turned on end to facilitate better drying due to the larger exposed surface area. Once they are sufficiently dry (i.e. not necessarily totally dry), they can be stacked to save space, leaving gaps for air circulation. A transparent plastic film can be used to provide protection from the rain and accelerate the drying process. By spanning the film over a makeshift timber framework or tent while allowing air to pass through it, one can exploit the air heating solar collector principle to accelerate drying of the bricks. Greenhouses are also suitable for larger brick manufacturers. Working panels and bricks Bricks and panels made of light earth with a bulk density of up to 900 kg/m³ can be cut with an (electric) knife. Heavier panels can be cut with a saw or a sharp axe. Heavier light earth bricks are cut to size with a masonry hammer or saw.

Dry construction  141 

540 Walls

541

Light earth masonry

Light earth masonry – like compacted walls – is used as infill within a timber frame and defines the enclosing perimeters of a space. It is non-loadbearing and may only sustain its own weight. In multi-storey buildings, loads from the wall are transmitted by a sill plate into the floor level. Light earth bricks are laid in brick courses and bond – in earth or lime mortar – in such a way that the load of the wall acts on the bricks in the same direction as the pressing or compaction during manufacture. The masonry infill is secured in place with triangular battens fixed to the vertical inner faces of both sides of the panel (figs. 232 and 233). In very thin wall panels, battens are laid horizontally at intervals between the courses. These have a triangular notch at both ends that matches the triangular battens so that they can shift vertically but not laterally. These are nailed to the brick course below. The timber frame need only comprise the loadbearing columns, windows and door posts, and ends of walls. Door and window casings can be inserted prior to bricklaying to serve as guides. Dry construction can be used in situations where wet compacted walls would not dry properly, such as when one side of the wall is a plywood panel, building board or insulation panel. Bricks should not, however, be laid directly against external cladding systems, as these should always be ventilated. The masonry mortar should have a similar bulk density as the masonry itself. For non-loadbearing applications, no special compressive strength is required. External walls should be laid in a light earth masonry mortar with short fibres, chopped straw or sawdust, internal walls with any earth mortar. Masonry infill panels that have yet to be Fig. 231 Internal masonry wall infill (Project 15)

142 Light Earth Building

541-01

Außen Outdoors

a)

a) Masonry, rendered Mauerwerk verputzt b) Masonry, insulation in wall core Mauerwerk, Kerndämmung c) Masonry, internal insulation Mauerwerk, Innendämmung Mauerwerk, Außendämmung d) Masonry, external insulation Mauerwerk, Außendämmung verkleidet e) Masonry, external insulation + cladding

b)

c)

d)

e)

f)

Innen Indoors Fig. 232 External masonry walls

Dry construction  143 

a) stud wall a)Plank Bohlenständerwand b) stud wall b)Post Kantholzständerwand c) stud wall c)Board Brettständerwand d) postKantholzständerwand stud wall d)Thin Dünne e)Horizontal aussteifende Bretteinlagen e) board laid in wall bei dünnen Wänden panel to stiffen thin walls

24

a)

8

12

b)

Fig. 233 Internal masonry walls

144 Light Earth Building

c)

d)

e)

rendered on their external face must be protected against rain as well as splash water, for example rain rebounding off scaffolding boards.

542

Panel infill in half-timbered structures

Masonry infill panels in half-timbered buildings are likewise secured with triangular battens nailed to the inside of the posts either side of the panel or via notches in the posts into which the masonry mortar flows. Long nails nailed into the verticals of the side posts after every three brick courses are a further traditional method of tying the panel to the frame. For half-timbered structures with exposed timbers, the masonry infill is set back from the front face by the thickness of the panel render or plaster. To provide a better mechanical key for two coats of lime render, the mortar joins are scratched out. Small bricks with a high proportion of mortar joins are better in this respect, especially if the bricks have smooth faces. Instead of applying two layers of lime render, an elastic fibrous earth undercoat plaster can be applied first, followed by a thinner 5 mm layer of hair-reinforced lime render, which attaches well to the earth undercoat (see chapter 642).

543

Thermally-insulating internal wall linings

An insulating internal wall lining can also be laid as brickwork, obviating the need for a supporting timber construction. The load from the weight of the brickwork must, however, be transmitted into the floor level below via a timber sill plate. In most cases, lightweight bricks in 2DF format (approx. 24 × 11.5 × 11.5 cm) with a bulk density of around 700 kg/m³ are used, laid in light earth mortar. Where the slenderness ratio of the wall plane height/thickness > 15, the wall plane needs to be anchored to the external wall to prevent buckling [Lehmbau Regeln 2009]. To avoid settlement, a height of no more than 2 metres per day should be laid to allow the earth mortar to dry sufficiently. Fig. 234 Panel infill with light earth masonry: a standard method of renewing timber frame panels

Dry construction  145 

542-01

8

2−3

Triangular batten Dreikantleiste

2−3

b) a) FFaserlehma) ibre-clay b) LKalkime render, putz 2 2 cm cm, putz 2 cm, plaster, 2 cm Kalkfeinputz Mörtelfugen fine-finish Mortar joins ausgekratzt 5−8topcoat mm lime scratched out render, 5–8 mm

Aufbereitung des Brick cut-off material Steinverschnitts can be recycled as earth zu Mauermörtel mortar Fig. 235 Timber-frame panel infill with earth brick masonry

Cavities between the wall lining and external wall or timber frame should be carefully and completely filled with light earth mortar (fig. 236). The internal wall lining can also be placed a few centimetres away from the wall. The cavity can then be successively filled with very lightweight, insulating light earth (400 kg/m³), for example pre-dried or very slightly moist woodchip light earth with each few courses of the wall lining. Alternatively a capillary conductive insulation material can be poured or blown-in after construction of the wall lining.

146 Light Earth Building

2−3

543-01

6−10

a)Cavity Hohlraumfüllung mitearth Leichtlehmmörtel a) filling with light mortar

c) distribution ­­ c)   ggeschoßweise eschossweise c)L oad via sill plate on each Abtragung über Abtragung über storey ­AAuflagerbohle uflagerbohle

b)  avity filling with woodchip light earth, b)C Hohlraumfüllung 400 kg/m³, or insulation 400 kg/m³ z.B. mit Holzleichtlehm oder Dämmstoff

Fig. 236 Masonry internal wall lining

Fig. 237 Earth block masonry

internal wall lining (Conluto®)

Dry construction  147 

544

Stacked walls

Stacked external walls In lightweight insulated timber constructions, stacked wall linings made of earth or light earth bricks improve the thermal mass, noise insulation and room acoustics. Walls do not sound hollow. With this method, bricks or panels are laid dry without mortar avoiding the introduction of moisture into the building construction. Where such wall linings are placed in front of wooden sheathing or boards, flat wooden battens are laid horizontally every three to four courses and screwed to the backing to clamp the bricks in place. The plaster base, for example open reed lath, is likewise fixed to these battens (figs. 239 and 240). A machine-applied earth plaster adheres through the plaster base to the bricks behind. Alternatively, the wall lining can be clad with earth building boards (fig. 241) and coated with a thin layer of plaster. Electrical cabling can be routed in this layer, as the layer of internal plaster provides reliable wind proofing of the timber frame wall. Figure 238 shows prefabricated timber frame elements with plywood sheathing on one side that have been filled internally with light earth bricks laid on edge in a thin bed of mortar with open vertical joins. To prevent the bricks from dislodging, thin horizontal planks have been laid every few courses that have notched ends to fit the triangular battens fixed to the vertical timber studs. An undercoat plaster is spray-­ applied to the entire wall surface – brick infill and timber posts – and a plaster rein­ Fig. 238 Stacked internal wall

l­ining in timber frame panels ­coated with a layer of undercoat plaster (see project 9)

148 Light Earth Building

Fig. 239 Prefabricated timber

frame house with stacked earth brick internal wall lining (Paproth)

Fig. 240 Dry laid bricks with reed

plaster lath (Paproth)

Fig. 241 Stacked internal wall lining clad with earth building board (Claytec®)

Fig. 242 Stacked internal wall lining

(see project 27)

Dry construction  149 

545-01

Wall junction Wandanschluß

Door frame junction Türanschluß

≥2 cm (Min. coverage of reinforcement stakes)

8—12

24

00 mm 1..00 tios 1 b p u

Fig. 243 Partition wall slabs (after Pollack/Richter)

forcement mesh embedded before a final thin topcoat of hair-reinforced lime plaster is applied (see project 9).

Stacked internal walls Internal wall panels can likewise be filled with dry-stacked bricks and clad on both sides with building boards. To improve rigidity, planks are laid at intervals and fixed to the vertical studs. Any kind of brick is suitable, including cheap extruded bricks that fall under Application Class III of the [Lehmbau Regeln 2009] (see fig. 321).

545

Partition wall panel elements

Partition wall panel elements are typically locally made in a flat mould with wood reinforcement bars (e.g. straight branches or battens) placed strategically in the form to lend the slab internal stability [Pollack/Richter 1952]. The thick panel elements are used upright in construction and laid like large masonry blocks (fig. 243).

150 Light Earth Building

550 Floors and roof inclines

551

Self-supporting floor slabs

Light earth can also be used to make floor slabs with wood-reinforcement. The floor slabs are reinforced in much the same way as staked floor constructions using timber battens or rods (see chapter 431). One should have roughly six battens, rods, round or half-round wooden poles (each 8 cm²) per metre of floor. The slabs are laid so that the timber reinforcement lies on top of the floor joists or on battens fixed to the sides of the floor joists or rafters. If the joist or rafter spacings vary, the slabs need to be made in different sizes, for example using an adjustable mould frame. Longer elements can also be sawn to size. The elements are laid in earth mortar with large joints filled with a fibrous earth mortar or light earth. The slabs can also be screwed through the timber reinforcement to the rafters from beneath (fig. 246 b). Recommended slab dimensions, according to [Pollack/Richter 1952] are: −− length: 50 to 80 cm −− width: 24 cm at a thickness of 14–18 cm −− 32 cm at a thickness of 8–14 cm. Slabs can also be given special design ­treatments, as seen in the vaulted coffering of the slab elements developed by A. Dilthey in Aachen (fig. 244).

Fig. 244 Floor slab elements with vaulted coffering (A. Dilthey)

Dry construction  151 

14—18

551-01

8—14

24

32

0

—8

50

a) Platten a) Slabs restauf onden top of joists Balken aufliegend

b) Slabs suspended b) Platten zwischen den between joists Balken eingelegt Fig. 245 Self-supporting floor slabs Fig. 246 Roof insulation with self-supporting slabs

1

3

1

2

2

4

a) Slabs/panels hung between rafters

152 Light Earth Building

b) Slabs/panels screwed to rafters

552-01

Slab Platte

Brick Stein

auf Bretta) P  Auflage laced between joists Einschub on intermediate floor

b) Auflage auf Schalung b) Placed on top of joists über den Balken on sheathing

Fig. 247 Floors weighted with bricks or slabs 552-02 Fig. 248 Roof insulation with laid light earth slabs or bricks

1 3

2

a)a)Panels/bricks slidauf behind sheathing Platten/Steine Schalung eingeschoben

3

2

1

on sheathing b)b) Panels/bricks Platten/Steineresting auf Schalung aufgelegt

Dry construction  153 

Fig. 249 Floor with bricks laid dry

between joists and joins brushed full with earth mortar

552

Earth slabs and bricks for floor weighting

Although non-reinforced light earth slabs are able to withstand compression and bending loads, thanks to the reinforcing effect of the straw fibres, they may only be used in non-loadbearing situations, e.g. placed flat on an intermediary floor of panelling between joists or on sheathing above the joists, or between supporting battens but without directly sustaining loads. This construction is similar to compacted light earth ceilings on lost formwork in floors and roof spaces. As slabs are easily cut or sawn to size, they can be made in one size and trimmed as required. Smaller-format bricks are well suited for weighting floors and can be heavier or lighter in weight depending on the desired properties. They are laid on a layer of building paper to prevent particles falling through the ceiling and the brick joins can be swept closed with a moist earth mix.

560 Dry construction Dry lining building boards made of a fibre-clay or light earth can be used as a replacement for conventional plasterboard to line the internal faces of external walls, internal partitioning walls, insulating wall linings, and for lining the interior of roof spaces and cladding ceilings. The joins between boards are reinforced with scrim tape bedded in earth mortar and after drying the entire surface is coated with a 5 to 8 mm thick single layer of fast-drying finishing plaster. All joins and corners should be reinforced with reinforcement mesh or scrim tape. Compared with conventional plasterboard, light earth building boards are more ecologically friendly to produce and have better physical properties: the softer material provides excellent sound insulation, which can be improved further (see chapter 840) through the filling of the void with insulation or heavy earth bricks (see chapter 544). Unlike the typical bright hollowness of hard dry lining boards, they vibrate at pleasantly low frequencies.

154 Light Earth Building

561-01

5

Außenwand verkleidet a)a)External wall with cladding

3

2

1

b)b)Internal wall, separate skins and supports Innenwand, getrennte Konstruktion

4

a) einfache Kantholzständer-Innenwand c)c)Internal wall, simple stud wall

Innendämmung d)d)Internal insulation

a) a) 11Earth building board, with hessian Lehmplatte 25mm,25 mm Fugenbewehrung tape over16cm joins 2scrim Dämmstoff 23Insulation, 16 cm Weichfaserplatte 34Softwood fibreboard Spachtelputz 3—5mm 45Smoothing plaster 3–5 mm Außenverkleidung hinterlüftet 5 External cladding, ventilated 26cm ts==26 cm 0,25W/m²K W/m²K UU==0.25 Qs = 93 kJ/m²K Q = 93 kJ/m²K

Fig. 250 Dry wall construction with earth building boards, a) and b) after Breidenbach

[Bundesverband GBW 1990]

561 Walls Internal walls A typical timber stud construction is clad with earth building boards. For situations with high sound insulation requirements, the wall can be divided into two skins with separate rows of supporting studs in a staggered arrangement, one for each face, to minimise sound transmission (fig. 250 b). Insulating wall linings Insulating wall linings increase the thermal insulation of external walls or walls to unheated rooms and can be used in both existing and new buildings. Building boards are screwed to a supporting construction of timber battens set forward of the existing wall surface (fig. 250 d). The cross section and spacing of the battens depends on the board thickness and is usually between 40 and 50 cm. The manufacturer’s guidelines

Dry construction  155 

Fig. 251 Cellulose blow-in insulation in cavity behind light earth building board (Claytec®)

Fig. 252 Internal insulation with earth building

Fig. 253 Earth wall heating panel elements (WEM®)

boards. The cavity is filled with insulation or woodchip light earth. Heating pipes are arranged in the wall skirting (see projects 11 and 12).

should be heeded. For thermally insulating wall linings, the resulting cavity between wall and lining is filled with insulation. To ensure the wall remains dry, only capillary conductive building materials are suitable, such as cellulose fibres made of recycled paper or natural fibre insulation materials (see projects 15 and 27). Lightweight naturally-­ moist or entirely dry, pourable woodchip or hemp light earth is likewise suitable (see fig. 252). The entire lining with boards and plaster can serve as an airtight layer. In such cases, the edges of the reinforcement mesh are fixed to the neighbouring construction element, ideally with clamping strips, to avoid gaps forming at junctions between elements. Wall heating elements Wall or ceiling heating panels are an elegant way of heating rooms, and can where appropriate also be used for cooling. Warmth that radiates from a surface is perceived

156 Light Earth Building

562-01

< 50 cm

Deckenbekleidung auf enger joists Balkenlage a)a)Ceiling between closely-spaced

b)b)Ceiling mounted on supporting battens, Deckenbekleidung auf Lattung a < 50d  800

Not easily flammable

Wood shavings 3)

> 1,600

Non-combustible

Sawdust 3)

> 2,000

Non-combustible

Hemp hurds, flax 3)

> 600

Not easily flammable

1) cf. DIN 4102-4: 1994-03 2) cf. DIN 18951 Sheet 1: 1951-01 3) After tests on the fire performance of earth building materials conducted as part of a diploma project at the Materials Testing Laboratory MFPA Leipzig according to DIN 4102-1 [Ziegert 1996] [Börjesson 1997].

Fig. 327 Fire behaviour of earth building materials, compiled from the DIN and research results

(cf. [Lehmbau Regeln 2009])

224 Light Earth Building

−− Light earth responds passively to the effects of flames, i.e. it does not contribute to the spread of fire. −− The formation of an “insulating” charred layer protects the surface of underlying materials from direct exposure to the flame, which increases with flame duration. −− Neither smoke, nor fumes nor perceptible combustion gases were produced. −− No particles fell from the specimens which could have contributed to the spread of fire. −− Compared with wood-wool magnesite-bonded panel, the fire behaviour was better with less charring and no smoke development. These results suggest that straw light earth could be classed as B1 “Not easily flam­ mable”. Woodchip light earth should have similar properties.

832

Fire resistance class

The fire resistance classes F denote the duration of fire resistance in minutes, for example F 30 = resistant to fire for at least 30 minutes. The fire resistance class for building elements that are not already classified in the DIN must be demonstrated through tests. To test the fire behaviour of light earth – in this case straw light earth – in situ in a construction with a facing plaster, a second fire test was conducted. Fire test 2 – Fire resistance class Two specimens were prepared with different bulk densities, each coated with an earth and sand plaster (fig. 326). The plaster surface was exposed to the flame for 45 minutes, specimen 1 from a distance of 7 cm, specimen 2 from a distance of 15 cm with a stronger flame. The flame breadth was 20 and 26 cm respectively. The specimens were tested in a chamber with closed rear face and insulated walls so that the specimen could not cool down, either at its sides or at the rear. The temperature at the rear side of the specimen was taken every five minutes at the height of the flame and at a depth of 10 cm beneath the plaster surface, as was the ambient air temperature in the chamber. The insulating effect of the light earth resulted in an only marginal increase in temperature at the rear of the specimen (10 cm beneath the plaster surface). No smoke development was observed. The plaster of specimen 1 glowed at the centre of the flame with a diameter of about 8 cm, while specimen 2, which was exposed to a stronger flame, glowed with a diameter of 16 cm. After the end of the flame test – after 45 minutes – the plaster surface of both specimens was still intact with the exception of tension cracks at the perimeter. The flame had the effect of firing the plaster into a water-impervious sliver of brick. The plaster of specimen 2 has reddened somewhat while the lime coating of the other specimen is still white in the flame core with black soot around it. Sawing apart specimen 2 caused the plaster to detach and fall off. The light earth material (500 kg/m³) is charred to a depth of just 6 cm, despite its low earth proportion (~25 vol.% lean earth) and thin layer of plaster. The charred layer of material did not detach. On specimen 1 (900 kg/m³) with an approximately 45 vol.% proportion of earth, the plaster remained attached.

Physical properties  225 

This test likewise served only as a means of approximating the fire behaviour of the material, and returned the following tentative results: −− Light earth with a plaster facing has fire-retardant properties. The fire resistance duration depends on the plaster thickness (ideally 15 to 20 mm), the bulk density and the wall or layer thickness. −− All timber elements of the structure enclosed by earth were largely protected against charring if covered by a 5 to 10 cm thick layer of plastered light earth material. For other fibrous earths (> 1,200 kg/m³), the plaster thickness could conceivably be thinner. −− A fire resistance class for walls and ceilings of F 30 to F 90 ought to be achievable. This needs to be demonstrated using suitable fire tests.

833 Classified timber building elements with earth infill In Germany, those building elements that are classified in [DIN 4102-4 1994] can be classified in fire resistance classes without having to provide extra certification. That the DIN also contains information on earth infill in walls and floors, alongside the various other timber slab and panel constructions used today, shows how long earth and timber have existed as a combination – even in contemporary norms. In the section on half-timbered constructions and timber joist floors, the DIN speaks of “Lehmschlag” (earth covering), which is probably a reference to traditional straw-clay on wattle or stakes. Walls Half-timbered walls are classed as F 30 B when the panels are entirely filled with earth (or wood-wool panel or masonry) and at least one side is completely covered, for example with a 15 mm layer of render (fig. 328). Floors and roofs The timber panel and timber joist floors classified in the DIN are predominantly particleboard or gypsum plasterboard constructions. A non-combustible mineral-­fibrebased material is prescribed as a necessary insulating layer. Traditional construction

Building element

Classification

Solid walls Solid masonry or compacted earth walls (Building Material Class A) at a thickness of 24 cm 1)

F 90 A

Half-timbered walls with panel infill Provided that the cross section of timber members exceeds 100 × 100 mm when exposed to fire on one side or 120 × 120 mm when exposed to fire on both sides, straw-clay panel infill, clad on at least one side, e.g. with 15 mm of plaster 2)

F 30 B

1) After DIN V 18954 1956 2) The individual conditions are noted in detail in DIN 4102-4 1994, Section 4.11

Fig. 328 Fire resistance classes of walls with earth building materials (cf. [Lehmbau Regeln 2009])

226 Light Earth Building

Building element

Classification

Timber joist floor with joists fully exposed (3 sides) to fire on the underside Weighted ceiling, e.g. with earth building materials of arbitrary thickness, dependent on joist cross section and spacing as well as sheathing material and sub-floor construction 1) Timber joist floor with covered joists Intermediate floor with earth layer ≥ 60 mm or transverse stakes with earth covering, depending on joint spacing, sheathing and ceiling cladding 2) Floor covering (only for structures exposed to fire from above) Covering of ≥ 50 mm earth 3)

F 30 B to F 60 B

F 30

  Notes: 1) cf. DIN 4102-4 1994 (5.3.2) and table 62, Conditions noted there in detail. 2) cf. DIN 4102-4 1994 (5.3.3) and tables 56 and 63, Conditions noted there in detail. 3) cf. DIN 4102-4 1970 (4.2)

Fig. 329 Fire resistance classes of floors containing earth building materials (cf. [Lehmbau Regeln 2009])

methods are not mentioned. In floors where the joists are enclosed within the floor construction, earth material can be used as the fire insulating layer on inserted panel floors. In the case of floors with exposed timber joists, the joist cross section and the material of the sheathing are deemed relevant for fire safety. The fill material is irrelevant in this respect and can therefore be made of earth or light earth (fig. 329). Other constructions made of earth building materials or light earth have not been tested and are not specified in the DIN norm. Compared with wood panelling constructions, the light earth panel infill of a timber structure has the advantage, from a fire resistance perspective, of being a homogenous, seamless element that has a much thicker construction depth. 12–30 cm thick walls with a render coat should qualify for at least F 30. Loadbearing elements that are embedded, i.e. enclosed by earth mass, are particularly well protected. Similarly, light earth floors that are plastered on the underside should also classify for at least F 30 when timber joists with smaller cross sections have a coat of protective plaster. For exposed timber beams, the values given in the DIN are applicable. Any stakes onto which an earth mix is applied should be completely enclosed by at least 5–6 cm of light earth covering. Plaster coats should be 15 mm, or even better 20 mm thick to be fire-retardant.

840 Sound insulation

841

Airborne sound insulation

Modern timber frame buildings are typically lightweight, multi-skin constructions lined with thin, flexible gypsum plasterboard or particleboard. Accordingly, current norms detail only the sound reduction indices of such lightweight constructions. Timber frame constructions with masonry or earth wall infill are not listed. To calculate the sound reduction index of earth infill material, one can use the values for other massive building elements with a corresponding mass per unit area.

Physical properties  227 

Wall thickness t 1) Bulk density

0.10

0.15

0.20

0.25

0.30

0.35 m

Sound reduction index, R’w (dB) 2)

kg/m3 1,800

47

51

54

56

1,600

46

50

52

55

57

1,400

45

48

51

53

55

57

1,200

44

47

50

52

54

55

1,000

43

46

48

50

52

53

800

41

44

46

48

50

51

600

40

42

44

46

47

49

1) Wall thickness without plaster 2) for a mean mass per unit area of the flanking building elements of 300 kg/m² assuming the same stiffness as the remaining wall materials

Fig. 330 Airborne sound insulation values, R’w, single-leaf plastered earth walls (see DIN 4109 1989

­Supplement 1, Table 1)

Earth building materials add mass to a timber frame structure and it is possible to achieve good sound insulation using a simple, single-skin construction. Compared with other massive wall infill materials – fired bricks, lightweight or aerated concrete blocks – all earth materials, and light earth in particular, are softer and more elastic. Sound vibrations are reduced and attenuated. As a heavy but soft building material, earth therefore offers excellent sound insulation properties. R’w (dB) 35

Normal speech is audible and intelligible

40

Normal speech is barely audible

45

Raised voices are barely intelligible

53

Singing barely audible

50

Normal speech inaudible, singing intrusive

60

Radio no longer audible

Fig. 331 Subjective impression of sound insulation values according to [Bobran 1967] p. 44

Weighted sound reduction index

Bulk density class

Layer thickness

R’w,R (dB)

kg/dm3

cm

0.7

2 × 17.5

57

62

67

0.9

2 × 15

1.2

2 × 11.5

0.5

2 × 24

0.8

2 × 17.5

0.9

2 × 15

1.2

2 × 11.5

0.9

2 × 24

1.2

17.5 + 24

1.4

2 × 17.5

1.6

11.5 + 17.5

2.0

2 × 11.5

Fig. 332 Airborne sound insulation values, R’w, two structurally-separate wall leafs,

plastered on each side with a 15 mm plaster coat according to DIN 4109 1989 Supplement 1, Table 6

228 Light Earth Building

Required airborne sound reduction index R’w

Required impact (footfall) sound reduction index L’n,w

dB

dB (required IPM) 1)

Multi-storey buildings with apartments and workspaces Floors between dwellings

54

53 (10)

Walls between dwellings

53

–

Floors

–

48 (15)

Party walls between houses

57

–

Single-family houses and terraced houses

1) IPM = Impact Protection Margin, Mi = 63 dB – L’n,w

Fig. 333 Stipulated minimum levels of airborne and impact sound insulation between

adjacent apartments or workspaces according to DIN 4109 1989 Table 3 Noise level ranges

Relevant external noise level

Required sound reduction index for external building element

dB (A)

R’w1) (dB)

I

≤ 55

30

II

56–60

30

III

61–65

35

IV

66–70

40

V

71–75

45

Fig. 334 Required levels of

sound insulation for rooms in residential buildings according to DIN 4109 1989 Table 8

1) for walls with up to 20 % glazing according to DIN 4109 Table 10

The airborne sound insulation of single-leaf walls increases with its surface mass per unit area. For sound-insulating partitioning walls and floors, one can use a dense, highly compacted infill material with a high mass per unit area (earth mixes with a high earth proportion), or one lays heavy earth bricks in the wall or floor. To prevent sound transmission between the joints or continuous pores in the structure, a coat of plaster is necessary on at least one side. The plaster coat adds further mass per unit area, improving the sound insulation further. The sound-insulating effect of different single-leaf plastered internal walls is shown in figure 330. Because sound is also transmitted via flanking building elements (floors, walls), their respective masses per unit area also contribute to the overall sound insulating effect. Party walls between adjacent apartments and houses Sufficient levels of sound insulation for party walls between adjacent apartments or houses can only be achieved with light earth using a construction with two parallel leafs that are structurally separate from one another. The necessary wall thicknesses are given in figure 332. Fire safety regulations must also be taken into account as firewalls may only be made of non-combustible building materials. In such cases, only heavy, non-combustible earth building materials (> 1,700 kg/m³) are suitable, for example earth brick masonry that can be laid over several storeys – without a supporting frame construction. Some regional building codes (for example in the German state of Hessia) do permit fire-retardant timber frame walls.

Physical properties  229 

External walls The primary determining factor for the sound insulation of external walls is the sound insulation of the windows and their proportional surface area with respect to the wall. As far as the wall surface itself is concerned, lightweight building materials such as light earth (600 kg/m³) provide sufficient sound insulation at normal wall thicknesses (fig. 330) to minimise the effect of the loudest external sound levels (fig. 334).

842

Sound insulation of timber joist floors (figs. 335 and 336)

Building regulations generally only require sound insulation of floors between separate dwellings and workspaces (fig. 333). In single-family houses, simpler constructions can also suffice. Where a floor and ceiling is directly fixed to the timber joists, airborne and impact sound (e.g. footfalls) is transmitted directly through the joists. In such cases, the mass of the fill material has less effect than the cross section and stiffness of the timber 842-01 joists. The required sound reduction index is barely achieved with joist cross sections of 16 × 22 cm (fig. 335). The stiffness of the timber joist ceiling is determined by the method 11 22

Floor and ceiling firmly fixed mit Balken Fußboden und Unterdecke fest verbunden to floor joists Auffüllung leicht oder schwer Light or heavy fill material Balken10/20 10/20 bis 16/22 Joists to 16/22

R´w < 52 TSM < 0 R’w < 52; Mi < 0

Fußboden getrennt Floor separated from joists 80mm mmheavy schwere Auffüllung: ≥≥80 fill material: Lehmoroder Sand (1800 kg/m³) Earth sand (1,800 kg/m³)

≥ 52 R’wR´w ≥ 52; Mi TSM ≥0 ≥0

separated from joists 33 Ceiling Unterdecke getrennt ≥≥80 fill material: 80mm mmheavy schwere Auffüllung: Lehmoroder Sand (1800 kg/m³) Earth sand (1,800 kg/m³) 44

Fußboden und Unterdecke getrennt Floor and ceiling separated from joists 80mm mmheavy schwere Auffüllung: ≥≥80 fill material: Lehmoroder Sand (1800 kg/m³) Earth sand (1,800 kg/m³)

R’wR´w ≥ 52; Mi TSM ≥0 ≥0 ≥ 52

≥ 55 ≥ 10 ≥10 R’wR´w ≥ 55; Mi TSM

Anmerkung: Note: Instead of a heavy fill material, an intermediate floor made of light earth (or straw-clay) of at least Anstelle dürften 150 auchkg/m²) Zwischendecken Leichtlehm the sameschwerer mass perAuffüllung unit area (approx. can provideaus similar levels of (oder soundStrohlehm) insulation: mit mindestens gleichem e.g. Light earthFlächengewicht 1,200 kg/m³ (ca. 150 t ≥kg/m2) 130 mmähnliche Schallschutzmaße ermöglichen: z.B. Leichtlehm 1200 kg/m³ dt ≥≥130 mm Light earth 800 kg/m³ 190 mm Leichtlehm 800 kg/m³ d ≥190 mm Using compacted light earth or earth reel floor infill, plastered on the underside, obviates the need for an Als Stampf- oder Wickeldecke ausgeführt und unterseitig verputzt, dürfte bei 1 und 2 Fehlboden intermediate floor and ceiling for cases 1 and 2. und Unterdecke entfallen können Fig. 335 Required levels of sound insulation for timber joist floors with intermediate floor, simplified

representation after DIN 4109 Edition 1962 Sheets 3 and 5

230 Light Earth Building

842-02

5

6

1

Weighted sound reduction index Rw 63 dB Bewertetes Schalldämm-Maß Rw == 63 dB              R’w,R R´w,R = 55 =dB55 dB

2

3

≥ 200 mm

4

≤ 600 mm

Weighted normalised impact sound pressure L’n,w,R = 53 dB (without floor covering) Bewerteter Norm-Trittschallpegel L´n,w,R =level 53 dB (ohne Bodenbelag) Impact protection margin = 10 dB Trittschallschutzmaß: TSMR = 10MdB i Holzbalken 1 1 Timber joists 2 Spanplatte (oder Schalung, d. Verf.) mitNut Nutund und Feder Feder 28 mm Spanplatte Schalung d.Verf.) mit == 28 mm Particle 2 2 board (or sheathing) with tongue and groove, d =dd28 mm Betonplatten -steine, flächenbezogene Masse mindestens 3 3 Concrete slabsoder or bricks laidininKaltbitumen cold bitumen,verlegt, mass per unit area: at least 140 kg/m² *) 140 kg/m² * 4 Impact sound insulation board, d ≥ 25 mm 4 dynamic Trittschalldämmplatte ≥ 25 mm stiffness s ≤ 15 dMN/m³ dynamische Steifigkeit s´≤15 5 Particle board, jointed or tongueMN/m³ and groove, d = 25 mm Spanplatte gespundet oder mit Nut und Feder d = 25 mm 6 5 Floor covering 6 Bodenbelag *) Author’s note: In place of concrete slabs, light earth or heavy earth bricks or slabs of a comparable * Anmerkung des Verfassers: Anstelle der Betonplatten dürften mit gleichem mass per unit area can also be laid in the floor without mortar: Flächengewicht trockenverlegte Leichtlehm- oder Schwerlehmsteine oder Platten Bulk density: verwendet werden können: 2,000 kg/m³ d = 70 mm Rohdichte: 1,800 kg/m³ d = 80 mm 2000 kg/m3 d = 70 mm 1,200 dd==115 1800kg/m³ kg/m3 80mm mm  800 dd==175 mm 1200kg/m³ kg/m3 115 mm

800 kg/m3

d = 175 mm

Fig. 336 Required levels of airborne and impact sound insulation for timber joist floors with weighted mass

after DIN 4109 1989 Supplement 1, Table 34

of panel construction, e.g. whether it has firmly wedged stakes or a dead floor laid on battens. Floor constructions with light earth or other fibrous earth material, can be filled over the entire height of the joists (e.g. compacted floor mass or earth reels, see chapter 432f) so that there are no ceiling voids that detract from the sound insulation. Floor cavities beneath the floor covering can be filled with sand, earth daub or insulating fill material to reduce the sound of footfalls. For timber joist floors with heavy earth fill material between the joists (intermediate inserted floors), one can refer to details given in earlier norms for heavy fill materials: The necessary airborne and impact sound insulation can be achieved for floors between separate dwellings provided the floor covering and/or ceiling are acoustically isolated from the joists, e.g. the floor should rest on an elastic layer of fibrous insulation material and may not be nailed through the insulation material, and a ceiling of flexible lining boards fixed on battens should be suspended from the joists by spring clips. The ceiling can also be plastered on a reed or timber plaster lath, or be made of plasterboard or earth building boards (fig. 335).

Physical properties  231 

Timber joist floors with a heavy mass laid over the joists, as shown in figure 336, provides a sufficient level of sound insulation. Instead of using concrete paving slabs bedded in a bituminous layer, the same level of sound insulation can be achieved by placing earth bricks or panels with a comparable mass per unit area on the floor sheathing. The placement of the mass at the top of the ceiling improves the sound insulation, and a suspended ceiling would improve the sound insulation still further.

850 Airtightness Normal wall constructions are as good as airtight. The extent of air exchange through “breathable walls” is not, as the misleading name suggests, sufficient to ventilate interior spaces. Uncontrolled ventilation, at the opposite extreme, should be avoided to prevent draughts and the suction of warm air out of the interior in windy weather conditions. On its own, light earth wall infill is only windproof upwards of a bulk density of 900 kg/m³. A wall with timber frame, panels and masonry can be made windproof by plastering the entire wall with a continuous coat of plaster or by cladding with building boards with filled joins.

860 Absorption of toxins The sorption capacity of earth has been cherished in natural medicine for years [Locher 1980]. Edible earth formulations help regulate gastro-intestinal functions of the body: soluble substances and gases, along with intestinal toxins and excess gastric acid are absorbed and bound within the material. The healing effect of earth-based fango packs is similar. It is unlikely that building with earth can have the same intensity of healing effect. The earth is dry, and only in the vicinity, whereas medicinal applications are wet and in direct contact with the body and/or the surfaces of inner organs. That said, how many other conventional building materials have the same non-toxic qualities as foodstuffs?

232 Light Earth Building

Projects Publication details for projects on p. 301

1

Conversion and extension of a half-timbered house (D)

Groß Gerau, 1980/81 Architect: Franz Volhard, Darmstadt Rediscovery of the light earth technique Technique: Straw light earth in shuttering Light earth building works undertaken by the client’s family, helpers and students. Duration of earth building: 7 weeks, total material: 58 m³ light earth Existing building: Renovation and renewal of half-timbered external walls, 30 cm, internal walls 12 to 20 cm thick. Intact panels were given a 15 cm thick internal insulating wall lining. The repaired straw-clay floors are lined with wood on the underside. Extension: Timber frame construction with 12, 25 and 30 cm thick straw light earth infill. The floors contain a 12 cm thick layer of compacted light earth material inserted in shuttering and plastered from below with a lime plaster. The outside of the building is clad with board and batten timber siding with a varnish of boiled linseed oil and earth-based paints. The internal surfaces are coated with trass-lime plaster. See also figures 69, 81, 124, 137, 163, 174, 175, 198, 199. Fig. 337 Cross section

Extension Fig. 338 Dining room during

Fig. 339 Dining room after

construction

completion

234 Light Earth Building

Existing building

Fig. 340 External wall cladding

Fig. 341 South façade with cladding (weather face)

901-02 CAD

30

Fig. 343 Wall and floor ­constructions

25

Außenwand External wall

12

Innenwand Internal wall

Innenwand Internal wall

12

Fig. 342 Erection of the extension

Leichtlehmstampfdecke Compacted light

earth floor

Projects  235 

2

New private house with workshop (D)

Darmstadt, 1983/84 Architects: Schauer + Volhard, Darmstadt Technique: Straw light earth in shuttering Light earth building works undertaken by a contractor in Darmstadt Private house as a timber post-and-beam construction with notched timber joists for visible inserted panel floor. All external walls, internal walls and floors have straw light earth infill. The earth was mixed into a clay slip using a plastering machine and mixed with the straw within the building shell using the spray method. The internal walls are plastered with a lime plaster, the external walls were given a coating of earth mortar and then clad with horizontal lap siding and painted light grey. Outbuilding (pottery workshop): Wall surfaces of unpainted smoothed earth-sand-chaff plaster. Finishing: Floorboards and stoneware tiles. The windows are arranged in the plane of the external cladding and open outwards. See also figures 21, 75, 111, 118, 119, 178, 262, 263, 324.

Fig. 344 Floor plans

236 Light Earth Building

Fig. 345 North façade

Fig. 346 Timber construction of the external walls

Projects  237 

902-03 CAD

Fig. 347 Topping-out ceremony Fig. 348 Detail sections through external

wall and floors

4

902-03 902-03 CAD CAD

4

1

3 2

1 External wall 26 cm straw light earth, 700 kg/m³, shuttered, internal lime plaster with limewash, external board and batten siding t = 33 cm, U = 0.6 W/m²K, Q = 310 kJ/m²K 2 Internal wall 12 cm straw light earth, 900 kg/m³, shuttered, lime plaster on both sides with limewash 3 Floor over ground floor 10 cm straw light earth fill material, 1,200 kg/m³, on exposed intermediate floor, floorboards with sand infill, tiles on screed in the bathroom

1 Außenwand 26 cm Strohleichtlehm 700 kg/m3 geschalt, innen Kalkputz 4 4 Stülpschalung mit Kalkanstrich, außen s=33 cm, U=0,6 W/m2K, Q=310 kJ/m2K 1 1 2 Innenwand 12 cm Strohleichtlehm 900 geschalt, beidseitig Kalkputz mit Kalkanstrich 3 Decke über Erdgeschoss 33 10 cm Strohleichtlehmfüllung 1200 auf sichtbarem Deckeneinschub, Dielenboden mit Sandschüttung, im Bad Fliesen auf Estrich 22 4 Decke zum unausgebauten Dachraum 10 cm Strohleichtlehmfüllung 700 auf sichtbarem Deckeneinschub, Dielenboden mit Dämmschüttung

4 Floor to the (unused) attic space 10 cm straw light earth infill, 700 kg/m³ on1exposed 1 Außenwand Außenwand 3 intermediate floor, floorboards with cavity insulation innen Kalkputz 2626 cmcm Strohleichtlehm 700 kg/m 3 Strohleichtlehm 700 kg/mgeschalt, geschalt, innen Kalkputz mit Kalkanstrich, außen Stülpschalung mit Kalkanstrich, außen Stülpschalung 2 2 s=33 cm, U=0,6 W/m Q=310 kJ/m s=33 cm, U=0,6 W/mK,2K, Q=310 kJ/mK2K Fig. 349 Internal view of timber 2 2 Innenwand Innenwand structure with pre-cut stakes for 1212 cmcm Strohleichtlehm 900 geschalt, beidseitig Kalkputz mit Strohleichtlehm geschalt, beidseitig Kalkputz mit the internal walls and inserted 351 Earth coating beneath Fig. 350 Light earth infill in walls 900Fig. Kalkanstrich intermediate floor panels wall siding and floors Kalkanstrich 3 3 Decke über Erdgeschoss Decke über Erdgeschoss 1010 cmcm Strohleichtlehmfüllung 1200 aufauf sichtbarem Strohleichtlehmfüllung 1200 sichtbarem Deckeneinschub, Dielenboden mit Sandschüttung, imim Bad Deckeneinschub, Dielenboden mit Sandschüttung, Bad Fliesen aufauf Estrich Fliesen Estrich 4 4 Decke zum unausgebauten Dachraum Decke zum unausgebauten Dachraum 1010 cmcm Strohleichtlehmfüllung 700 aufauf sichtbarem Strohleichtlehmfüllung 700 sichtbarem Deckeneinschub, Dielenboden mit Dämmschüttung Deckeneinschub, Dielenboden mit Dämmschüttung

238 Light Earth Building

Fig. 352 Horizontal lap siding

Fig. 353 Backyard

Fig. 354 Children’s room

Projects  239 

3

Earth building settlement: Domaine de la Terre, L’Isle d’Abeau (F)

Light earth houses in the housing settlement Le Domaine de la Terre, Villefontaine (Isère), 1982–85 Architect: Paul Wagner, Atelier 4, Gap (Hautes-Alpes) Consulting: CRAterre (International center for Earthen Architecture) Construction firm: Marius Guédy Technique: Straw light earth with sliding formwork The Domaine de la Terre earth building settlement is part of a French pilot project from the 1980s and was conceived as a response to the international energy crisis. Initiated by the architect Jean Dethier at the Centre Georges Pompidou and realized through a commission from OPAC (Isère) and EPIDA (Etablissement Public d’Aménagement de la Ville nouvelle de l’Isle d’Abeau), it was supported by the CRAterre research group (International centre for Earthen Architecture) and aimed to explore the technical and architectural possibilities of earth building methods. 65 residential units were realised on a 2.2 hectare site divided into 12 plots. Three different earth building techniques were used: rammed earth (pisé), compressed, stabilised earth blocks (CEB) and straw light earth in wet construction. The walls of the six light earth buildings were made in 25 cm thick frames with sliding formwork, clad externally with wood cladding and internally with hollow brick panels. See also figure 28.

Fig. 355 Building shell

240 Light Earth Building

Fig. 356 Timber-clad external walls

Fig. 357 Aerial view Fig. 358 Ground floor

(architect: Paul Wagner, redrawn)

Fig. 359 Timber skeleton frame

Projects  241 

4

New youth community building (D)

Jugendhof Bessunger Forst, Roßdorf, 1985/86 Architects: ASAD Funke, Geelhaar, Heinrich, Darmstadt Consulting: Franz Volhard, Darmstadt Earth building works undertaken by teams of young people at the centre under expert instruction The external walls of the two-storey stud wall construction with twin stud arrangement were made of 30 cm thick straw light earth, the internal walls of earth brick masonry from light earth bricks made the year before which were laid in autumn and winter. The floor infill is likewise a straw light earth mix compacted on an inserted intermediate floor. The internal surfaces are plastered, the external surfaces clad with board and batten siding and painted a light opaque colour. See also figures 114, 129, 164, 225–229, 257.

Fig. 360 Construction of the south façade (architect: ASAD, redrawn)

Fig. 361 Floor plan (architect: ASAD, redrawn)

242 Light Earth Building

Fig. 362 Community building

Fig. 363 Construction of the gable

façade (architect: ASAD, redrawn)

Fig. 366 Masonry internal walls. Fig. 364 Twin post stud

Fig. 365 Compacted external

­construction

walls

Made with bricks made the previous year (see fig. 225f)

Projects  243 

5

Barn conversion (D)

Offenbach, 1988/90 Architects: Schauer + Volhard, Darmstadt Technique: Straw light earth in shuttering and straw light earth on stakes Earth building works and plastering undertaken by Lehmbau Breidenbach, Viersen and by lay contributors under expert instruction The old brick masonry external walls were given a 16 cm thick internal wall lining of straw light earth to improve its thermal insulating properties. The internal walls are made of straw light earth on stakes, the timber joist floors with straw light earth reels. The internal earth surfaces received an earth undercoat plaster and a finishing coat of lime plaster applied with a Japanese trowel. Finishes: Slate floor on the ground floor, untreated floorboards on the upper floor, steel and wood windows, with the barn doors reconfigured as large retractable shutters. See also figures 110, 296.

Fig. 367 Floor plan, top floor

Fig. 368 Longitudinal section

Fig. 369 Light earth internal wall

lining

244 Light Earth Building

Fig. 370 Wrapped internal wall

Fig. 371 Wall and ceiling, plastered

Fig. 372 Façade facing onto the courtyard

Fig. 373 Lime fine-finish render with earth ­undercoat plaster

Projects  245 

6

House extension (D)

Darmstadt, 1989/90 Architects: Schauer + Volhard, Darmstadt Technique: Timber frame with earth brick panel infill Earth building works undertaken by the client The main structure is a post-and-beam frame construction made of glue-laminated timber members at column spacings of 2–3 metres. All external and internal walls have 12 cm thick earth brick masonry infill laid in earth mortar with an additional external layer of isofloc wood-fibre insulation mounted in front of the loadbearing structure. The façades are clad with painted vertical board and batten siding. Finishes: Wooden floorboards and stoneware tiles, white-stained wood ceilings and a steel conservatory. Fig. 374 View from the garden

Fig. 375 Floor plan, top floor

Existing building Fig. 376 Main and secondary timber structure,

south façade

246 Light Earth Building

Fig. 377 South façade with

cladding

Fig. 378 Upstairs room

Fig. 379 Living room

Projects  247 

1 External wall Lime-gypsum plaster, Earth brick masonry 2DF, 1,800 kg/m³, cellulose insulation, softwood fibreboard, external cladding, wood t = 31 cm U = 0.3 W/m²K, Q = 290 kJ/m²K

1

2 Internal wall Earth brick masonry 2DF, 1,800 kg/m³, lime-gypsum plaster 3 Floor Floorboards, weighted floor with earth bricks NF, 1,800 kg/m³, softwood fibreboard, wood sheathing on timber joists

2

3

1

Fig. 380 Section through façade

Fig. 381 Main structural timber

Fig. 382 Spray-applied cellulose

Fig. 383 Exposed timber frame

frame

insulation

on internal wall

248 Light Earth Building

7

Cowshed and barn conversions (F)

Cowshed in Le Molay-Littry (Calvados), 1985 Barns in Sartilly (Manche), 1986 Design and instruction: Association Régionale Biomasse Normandie ARBN, Caen, Christian Delabie Technique: Straw light earth in metal shuttering Earth building works: self-build with additional help from neighbours All the buildings employ prefabricated ladder and plank stud frameworks. The wall infill was constructed before construction of the roof, allowing the straw light earth to be trodden into the form from above. An air-permeable expanded metal mesh formwork was used to allow the material to dry while the extensive surface shuttering was still in place. The material was prepared using the available farm machinery, and the con­ struction faced with timber cladding.

an earth pit with a manure slurry mixer

Fig. 385 Pumping into a ­tank-trailer

Fig. 387 Shifting the shuttering panels

Fig. 386 Pouring the clay

slip onto the flatbed of a manure spreader

Fig. 388 Metal shuttering (after ARBN)

150 6 60

Fig. 384 Preparing the slip in

3

2

5 4

1 1 2 3 4 5 6

Frame 40 × 40 Expanded metal mesh Hollow-profile socket connector Hook connectors Tie rod (self-cleaning) Holes for tie rods

Projects  249 

8

Summerhouse (S)

Mauritzberg, Sweden, 1992 Architect: Prof. Sverre Fehn†, Oslo Research project at the Faculty of Architecture, Helsinki University of Technology under Professor Bengt Lundsten Work group: Leticia Achcar and Mika Westermarck, Helsinki Technique: Masonry construction made of straw light earth blocks Using a modular timber construction of planks, a series of light earth blocks were prefabricated to match the dimensions of the column intervals. The blocks enclose the timber posts within the wall. The internal face is plastered with lime plaster, the external face with an earth plaster with chopped fibres.

Fig. 389 Floor plan

Fig. 390 Living room

250 Light Earth Building

Fig. 391 Kitchen

Fig. 392 Summerhouse

Fig. 393 Section

Fig. 394 Light earth blocks

Fig. 395 Modular compaction mould

Projects  251 

9

Atelier (D)

Darmstadt, 1996 Architects: Schauer + Volhard, Darmstadt Technique: Timber frame construction with light earth brick infill (stacked technique) and fibre-reinforced earth undercoat plaster Earth building works: Lehmbau Breidenbach, Viersen Construction: Floor slab, walls and roof made of timber panel elements with plywood sheathing and isofloc cellulose blow-in insulation in the cavities of the floor and roof panels. External thermal insulation with reed mat boards and lime topcoat render. Finishes: Oiled oak floorboards, lime paint, built-in cupboards as space dividers Function: Sculptor’s atelier with a living space on the gallery, kitchenette and bathroom See also figures 238, 259, 281.

Existing Altbau building

Fig. 396 Floor plan, ground floor

252 Light Earth Building

Fig. 397 View from outside

Fig. 398 Section

Projects  253 

Fig. 399 Section through façade

3 1

2

1 External wall Fibrous lime render, 5 mm, on earth undercoat plaster, timber frame elements with light earth brick masonry infill 2DF, 700 kg/m³, stacked, plywood, 10 cm external insulation of reed mat boards, external render. t = 30 cm, U = 0.39 W/m²K, Q = 250 kJ/m²K 2 Internal wall Timber studs, light earth brick masonry infill 2DF, 700 kg/m³, lime plaster on earth plaster undercoat on both sides 3 Floor to roof Fine-finish lime plaster, earth undercoat plaster on reed plaster lath, plywood, timber I-joists with cellulose pour-in insulation, plywood, ventilated roof

Fig. 402 Corridor during Fig. 400 Timber building shell

254 Light Earth Building

Fig. 401 Stacked wall lining

construction

Fig. 403 Atelier

Fig. 404 Corridor

Fig. 405 Gallery

Projects  255 

10

Earth house in Maria Rain (A)

Maria Rain, Austria, 1995–1997 Architect: Eva Rubin, Maria Rain Technique: Straw light earth using locally-sourced earth Earth building works undertaken as self-build project Timber frame structure with wide column spacing, with light earth compacted in sliding formwork for the external walls, internal walls and floors. The internal faces are equipped with wall-heating registers embedded in an earth plaster, the external faces in untreated larch cladding. The combination of thermally insulating light earth external walls, the thermal mass of the internal walls and the radiant wall heating contribute to creating a pleasant interior climate and reducing the heat demand. See also figure 88.

Fig. 406 Kitchen Fig. 407 Stairs Fig. 408 Living room

256 Light Earth Building

Fig. 409 View from outside

Fig. 410 Floor plan, upper floor (architect: Eva Rubin, redrawn)

Projects  257 

11

Historical renovation and extension of a listed building (D)

Mörfelden, 1998 Architects: Schauer + Volhard, Darmstadt Techniques: Earth reels, woodchip light earth (wet insertion), light earth building boards, stacked walls using earth bricks, earth undercoat plaster. Earth building works: Natürliches Bauen, Gerd Meurer, Koblenz Renovation: Removal of later additions to the building and reconstruction of the building using traditional techniques, including earth reel floors. Addition of a 15 cm thick insulating wall lining to the internal face of the external walls using woodchip light earth and light earth building boards as lost formwork. Extension: Panel-frame construction with cellulose blow-in insulation. Earth dry lining boards were used to clad external walls, internal walls and the roof. The construction meets “low energy standard” requirements. Finishes: Painted wall finishes with lime-casein paint based on historical finds in the old building from the Baroque period. Wood floorboards and stoneware tiles (both partially from recycled material). Function: Socio-psychiatric advice centre with sheltered housing. See also figures 194, 249, 252, 255, 261.

Fig. 411 Internal wall lining with woodchip light earth behind a lost formwork of earth dry lining boards

258 Light Earth Building

Fig. 412 Interior with colour washed lime plaster

Fig. 413 View from the road (projects 11 + 12)

Extension

Existing building

Fig. 414 Floor plan, upper floor

Projects  259 

Fig. 415 Junction between the old building and new extension

4

Fig. 416 Section through façade of extension,

timber panel construction 1 External wall Fibrous lime plaster, 5mm on earth dry lining boards, stacked wall lining, earth bricks, 1,800 kg/m³, cellulose insulation in timber panel elements, external timber siding with plaster baseboard at wall base, rendered t = 33 cm, U = 0.25 W/m²K, Q = 240 kJ/m²K

2 3

2 Internal wall Timber stud wall with dry stacked earth bricks NF,  1,800 kg/m³, clad with earth building boards, 5 mm lime plaster

1

1

3 Noise-insulating floor Floorboards or tiles on dry screed in the bathroom, impact sound insulation, OSB sheathing, timber joists with heavy earth bricks NF, 1,800 kg/m³, on inserted intermediate floor, earth building boards mounted on spring clips as ceiling cladding, earth plaster 5 mm, limewash 4 Roof Lining with earth building boards, earth plaster 5 mm, cellulose insulation between rafters

Fig. 417 Erection of the timber panel elements

260 Light Earth Building

Fig. 418 Stacked wall

Fig. 419 Interior of the extension: stacked internal walls and roofspace cladding with earth dry lining boards

12

Historical renovation of a listed building (D)

Mörfelden, 1998 Architects: Schauer + Volhard, Darmstadt Techniques: Straw-clay on wattle, earth reels, woodchip light earth (wet insertion), light earth building boards, stacked walls using earth bricks, earth undercoat plaster. Earth building works: Natürliches Bauen, Gerd Meurer, Koblenz Renovation and restoration of original structure using traditional techniques including straw-clay panel infill and earth reel floors. Addition of a 15 cm thick insulating wall lining to the internal face of the external walls using woodchip light earth and light earth building boards as lost formwork. Finishes: wood floorboards and re-used stoneware tiles, lime fine-finish plaster and lime wash. Function: Archive and library for the local history museum and an apartment in the attic. See also figures 145, 171, 190, 192, 193, 289

Fig. 420 Floor plan, upper

floor

Fig. 421 View from

the road

Projects  261 

4

1 External wall Fibrous lime plaster, 5 mm, earth building board as lost formwork for naturally-moist woodchip light earth infill, 600 kg/m³, half-timbered structure with straw-clay on wattle or light earth brick masonry infill NF, 1,200 kg/m³, on façades sheltered from the weather, exposed timber frame, lime render on panels. t = 31 cm, U = 0.8 W/m²K, Q = 340 kJ/m²K

2

3

2 Internal wall Half-timbered structure with old straw-clay panels or light earth brick masonry NF, 1,200 kg/m³, lime plaster on both sides. 1

3 Floors Floorboards, sand fill material, existing earth reel floor repaired and augmented, lime plaster, with exposed beams in some rooms 4 Roof conversion Lining of roofspace with earth building boards plus 5 mm earth plaster, limewash, cellulose insulation between the rafters, roof covering

Fig. 422 Section through façade Fig. 423 Batten construction for internal wall lining,

and earth masonry panel infill with light earth bricks

262 Light Earth Building

Fig. 424 New straw-clay panel infill with ­comb-scored substrate

Fig. 425 View from the courtyard

Fig. 426 Stairs

Fig. 427 Roofspace clad with earth building boards

Projects  263 

13

Single-family home in Raisio (FIN)

Raisio, Southwest Finland, 1998 Architect: Teuvo Ranki, Turku Engineer: Mauri Maanpää, Turku Technique: Straw light earth blocks in a modular timber construction Contractor: Puu ja Savi, Pöytyä Timber frame structure with twin post arrangement 2 × 50 × 125 mm. Masonry wall infill with straw light earth blocks, 450 kg/m³, made by the contractor. The external surfaces are plastered with a lime render, the internal surfaces with earth plaster. See also figure 210. 922-04 Fig. 429 Sketch of construction principle (after Teuvo Ranki) Light earth block, Leichtlehmblock 60 × 40 × 15 cm 60x40x15 cm External cladding Außenschalung

Innenputz Internal plaster

Fig. 428 Entrance

264 Light Earth Building

Installation Montage derof internal Innenpfosten nach the posts after laying dem Mauern blocks

Fig. 430 Insertion of the straw light earth blocks

Fig. 431 View of the east façade

Fig. 432 Floor plan, ground floor (architect: Teuvo Ranki, redrawn)

Projects  265 

14

Littlecroft, demonstration building for a research project (UK)

Eildon, Scottish Borders, Scotland, 2002 Architects: Chris Morgan, Gaia Architects, Edinburgh (Chris Morgan now of Locate Architects, Dunblane) Consulting: Advice provided by an international team of experts Technique: Straw light earth and woodchip light earth in shuttering along with prefabricated blocks made of light earth Earth building works: Chris Morgan, Charles Dobb, Becky Little The first light earth house to be built in the UK with regulatory approval. A twin-stud wall structure with timber joist floor resting on individual foundations. The walls are made of different types of light earth techniques including masonry made of prefabricated woodchip light earth and sawdust-reinforced mortar, straw light earth and various different woodchip light earth mixtures in shuttering. Straw light earth is used as a substrate for the green roof. The roof and floor are insulated with sheep’s wool and the plaster indoors and out is an undercoat plaster of earth with chopped fibres and sand followed by a topcoat fine-finish plaster with animal hairs and lime wash. The eaves project 60 cm protecting the wall surfaces.

Fig. 433 Floor plan (architect:

Gaia Architects, redrawn)

Fig. 435 Straw light earth in Fig. 434 Timber frame

266 Light Earth Building

shuttering

Fig. 436 Different wall fillings

Fig. 437 View from the garden

Fig. 439 Section through façade

(Gaia Architects)

Fig. 438 Interior

Projects  267 

15

Sandberghof community-oriented housing (D)

Darmstadt, 2007 Architects: Schauer + Volhard, Darmstadt Technique: Straw-clay on wattle, earth reels, light earth building boards, light earth bricks, earth plaster Earth building works: Heckwolf, Dieburg; Neumann, Pfungstadt Renovation of a courtyard ensemble with a Baroque-era half-timbered house from 1756 using old and new techniques: Repair of the straw-clay earth panels of the external and internal walls and completion of the joist floors with earth reels. Internal insulating wall lining along the walls and in the roof filled with blow-in cellulose insulation and natural fibre insulation materials, clad with light earth building boards, in ancillary spaces with gypsum fibreboard. New internal walls continue the half-timbered structure with light earth brick panel infill for all external and internal walls using normal format (NF) bricks bedded in earth mortar. The external walls are rendered across their entire surface with a pigmented lime external render on a reed plaster lath applied to the entire half-timbered façade. The outbuilding made of irregular stone blocks was also given an internal insulating wall lining with earth building boards or gypsum fibreboards plus cellulose blow-in insulation. Finishes: Stoneware floors and wooden floorboards, lime and earth plasters. See also figures 170, 231, 258, 268, 269, 280, 300.

Fig. 440 Section through half-timbered building (residential section)

Apartment Wohnung 33

Wohnung 22 Apartment

Wohnung 11 Apartment

268 Light Earth Building

Fig. 441 View from the road

Fig. 442 Floor plan, ground floor

Projects  269 

Fig. 443 Section through façade

2

1 External wall with internal insulation, lime plaster 5 mm on earth building boards, cellulose insulation, 60–100 mm, earth levelling plaster, half-timbered construction with old straw-clay panel or light earth brick masonry infill NF, 1,200 kg/m³, external render over full façade on plaster lath base t = 25 cm, U = 0.4 W/m²K, Q = 233 kJ/m²K

3

2 Internal wall, existing half-timbered structure repaired and extended, earth brick masonry infill, 1,200 kg/m³, lime plaster on reed plaster lath 3 Floor above ground floor separating dwelling, floorboards on impact sound insulation layer, existing earth reel floor repaired and augmented, lime ceiling plaster on reed board base

1

Fig. 444 Batten construction for

Fig. 445 Internal light earth brick

internal wall lining

masonry

270 Light Earth Building

Fig. 446 Earth reel floor

Fig. 447 Internal insulation

of the rubble stone wall made it possible to leave the wall exposed outside.

Fig. 448 Half-timbered building, through-coloured

lime render on reed plaster base. The use of internal wall insulation made it possible to retain the building’s external appearance (see ill. 268 f)

Fig. 449 Staircase landing

Projects  271 

16

Single-family home in Sweden (S)

Järna, Sweden, 2006 Architects: Walter Druml, Jakop Lindergård, Prisma arkitekter Consulting: Johannes Riesterer, Svenska Jordhus Technique: Woodchip light earth with sliding formwork Earth building works: The clients together with Svenska Jordhus Loadbearing stud construction with 35 cm thick woodchip light earth mixed out of locally-sourced earth and lightly compacted in screw-on sliding formwork. The rich earth made it possible to create relatively lightweight mixes (approx. 600 kg/m³). All surfaces inside and out are a fibrous earth plaster with no further covering or treatment. The earth building work was completed within the space of one week by a team of four.

Fig. 450 South façade Fig. 451 Internal walls with earth plaster Fig. 452 Floor plan (architect:

Prisma arkitekter, redrawn)

272 Light Earth Building

17

Church in Järna (S)

St. Christopher’s Church in the Christian Parish of Järna, Sweden, 2008 Architects: Walter Druml, Prisma arkitekter Consulting: Svenska Jordhus, Johannes Riesterer Technique: Straw light earth blocks, compacted straw light earth in the wall, earth plasters (inside) and renders (outside) Earth building works: The clients together with Svenska Jordhus The timber construction of the church comprises densely placed connected squared timbers 8 × 10 cm that are visible from within. The wall infill was undertaken as a self-build initiative and erected as masonry using hand-made straw light earth bricks made on site with a hand-operated press (bulk density ~500 kg/m³). The walls of a neighbouring building are made of wet inserted straw light earth compacted in shuttering. The slightly domed ceiling of the entry space, made of compacted straw light earth has been left visible without a plaster coat. The walls inside and out have been coated with a fibre-reinforced earth plaster.

Fig. 453 View of church

Fig. 454 Vestibule with exposed

straw light earth floor infill on the ceiling

Fig. 455 Floor plan (architect: Prisma arkitekter, redrawn)

Projects  273 

18

Guesthouse in New Mexico (USA)

Tesuque, New Mexico, 2001 Architects: Paula Baker-Laporte, EcoNest Architecture Technique: Straw light earth in shuttering (LSC Wall System) Earth building works: EcoNest Building Company, Robert Laporte Development of a straw light earth wall system (LSC Wall System) as part of an inte­ gral concept for a house construction method according to building biology principles. The “EcoNest” system is individually adaptable to different needs. The 30 cm thick external walls made of straw light earth are placed on stem walls made of woodinsulated concrete mantle blocks that minimise the use of concrete. The walls are held in a non-loadbearing matrix framework of ladder trusses with horizontal bamboo stabilising bars and enclose the entire building, leaving the timber framework visible on the inside. The walls are plastered inside and out with earth plaster, and protected by a 1.20 metre wide roof overhang.

Fig. 456 Mixing area with tumbler with gravity feed slip

Fig. 457 Tumbling with gravity feed slip from the silo

Fig. 458 Inside the tumbler

Fig. 459 Hoppers ready for filling

274 Light Earth Building

Fig. 460 View from the south

Fig. 461 Floor plan (architect: Econest, redrawn)

Fig. 462 and 463 Living room, earth plaster panels between exposed timber frame

Projects  275 

19

Prajna Yoga Studio in New Mexico (USA)

Santa Fe, New Mexico, 2008 Architects: Paula Baker-Laporte, EcoNest Architecture Technique: Straw light earth in shuttering (LSC Wall System) Earth building works: EcoNest Building Company, Robert Laporte The floor plan design, dimensioning and orientation follow the architectural and building tradition of Japanese Zen and Indian Sthapatya Veda. The LSC (Light Straw Clay) Wall System is a custom system developed by Robert Laporte and has been perfected since the 1990s in successive projects and workshops. It comprises a combination of the use of tumbler, mixer, silo, forklift and hoppers to prepare and load the material and an innovative framework and shuttering system for producing the walls. The characteristic EcoNest Architecture is inspired by Japanese houses with exposed timber frame in the interiors and smooth earth plaster surfaces, and is carefully detailed from beginning to end.

Fig. 464 LSC System with ladder stud construction

Fig. 465 External wall with full-surface shuttering on

for the straw light earth external walls

the internal face and external sliding formwork

Fig. 466 Wide scaffold with aluminum walkboard for

Fig. 467 Typical LSC corner detail with ladder studs

filling the upper wall sections

and inserted bamboo reinforcement bars

276 Light Earth Building

Fig. 468 Meditation room

Fig. 469 Floor plan (architect: Econest, redrawn)

Fig. 470 Con­ struction of the light earth external walls (Econest, redrawn)

Projects  277 

20

Single-family home in Wisconsin (USA)

Wisconsin, USA, 2008 Architect: Design Coalition Inc. Architects, Madison, Wisconsin, USA Technique: Straw light earth in sliding formwork Development of a cost-effective, environmentally-friendly and energy-efficient wall system made of light earth that is able to withstand the extreme climate of Wisconsin (hot and humid summers and very long, cold winters). The project is state-funded by the Housing and Urban Development Office of Native American Programs. The structure is a stud construction with 30 cm thick straw light earth walls lightly compacted in mobile, screw-fixed shuttering. The light earth was mixed in a specially developed tumbler mixer. The internal surfaces are earth plaster, the external surfaces lime render or timber clad. The locally-sourced rich earth made it possible to mix very lightweight light earth mixtures. See also figures 78, 100, 101.

Fig. 471 Floor plan (architect: Design Coalition, redrawn)

Fig. 472 Instruction of Native Indian helpers

278 Light Earth Building

Fig. 473 Communal compaction

Fig. 474 The house in winter

1 External wall 29 cm straw light earth, 200 kg/m³, shuttered, horizontal timber inserts, internal earth plaster, external fibre-cement cladding, s = 33 cm, U = 0.3 W/m²K, Q = 110 kJ/m²K 2 Floor Timber I-joists, plywood floor, plasterboard lining 3 Roof Lightweight lattice beam rafters, cellulose insulation

3

2

1

Fig. 476 Construction of the gable wall

Fig. 475 Section through

façade Fig. 477 Lightweight timber skeleton frame showing mixing area with drum tumbler mixer

Projects  279 

21

Single-family Home in Carla Bayle (F)

Le Carla Bayle (Ariège), 2010 Architect: Juan Trabanino, Toulouse Contractor: RAH Inventerre SCOP, Francarville (Haute-Garonne) Technique: Straw light earth in shuttering The house is semi-submerged into the sloping site on the north side and protected by a reinforced concrete retaining wall. The living area has 30 cm thick external walls made of straw light earth with a bulk density of 250 kg/m³ (U = 0.3 Wm²K) placed on top of a lightweight concrete foundation. The shuttering is set back from the ladder studs so that the light earth mix envelops the entire timber construction. The roof is insulated with straw. The internal walls are coated with earth plaster, the heating is stove-fired and warm water is heated by solar collectors.

Fig. 478 Floor plan (architect: Juan Tabanino, redrawn) Fig. 479 Mixing area

280 Light Earth Building

Fig. 480 Continuous straw light earth wall

Fig. 481 Lightweight twin-post skeleton frame construction

Fig. 482 Timber construction of gable wall

Fig. 483 View of the east façade

Projects  281 

22

Twenty houses made of straw light earth (F)

Hameau des Buis, Lablachère (Ardèche), 2002–2010 Architect: Pierre-Henri Gomez, Prunet (Ardèche) Consulting: Rodrigue Andorin Technique: Light earth in shuttering and light earth blocks prefabricated on site The first twenty houses of the village for the association “La Ferme des Enfants” (school, farmhouse, vegetable garden) were constructed communally under professional instruction. The houses are insulated with straw bales, clad with wood-based panels and rendered or faced with timber cladding. Light earth blocks were used for the internal walls with bulk densities of 300 kg/m³ and 1,000 kg/m³. The construction process was accelerated through the use of agricultural machinery, a steel container for mixing and sieving the slip, and a manure spreader (at a rate of 4 m³ light earth per hour). The 12 cm thick internal walls were compacted in lost formwork over summer, with earth blocks used in the remaining months of the year. The blocks, made in dismantlable moulds, were then dried under a foil tent roof. The internal partitioning walls are plastered with earth plaster with fibrous and sand aggregates.

Fig. 484 View from the south Fig. 485 Manufacture of blocks in a battery mould

282 Light Earth Building

Fig. 486 Earth blocks drying

23

Conversion of a rural house in Normandy (F)

Hotot-en-Auge (Calvados), 2010 Architect: Sophie Popot Consulting: Christian Sutter, AsTerre Technique: Straw light earth in sliding formwork Earth building works: Teams of between 3 and 5 labourers (mostly bricklayers and carpenters) as well as members of the ARPE BN association: Gwenolé Auvray and Vincent Pastorini. Existing structure: Half-timbered structure in the traditional regional manner (vallée d’Auge) with tightly spaced posts (trame serrée). Building material: Barley straw from the previous year, local earth, soda, water, and light earth walls (bulk density 800–900 kg/m³, 500 kg/m³ in the roof) with a thickness of approx. 30 cm.

Fig. 487 Elevation (after a drawing by S. Popot)

Fig. 489 External walls during Fig. 488 Completed building shell

construction

Projects  283 

24

House rebuilding in Haiti

Vicinity of Port au Prince, Haiti, 2010 Reconstruction of rural houses destroyed after the earthquake on 12 January 2010. Financing: Five Haitian organisations belonging to the PADED Platform for Sustainable Development (Plateforme Agroécologique pour le Développement Durable) contributed to the reconstruction of 4,000 small houses, with financial support from Misereor. Consulting: Laboratoire CRAterre-ENSAG, Grenoble, France The houses develop a local building culture into an intelligent rural architecture that is adapted to rural, agricultural ways of life. The farmers and their families and neighbours erect the houses in an organised form of mutual assistance (Kombit). Misereor provided financing for a basic 22 m² large module with 1 room and porch, but the buildings can be larger. This made it possible for local inhabitants to learn the construction techniques so that they can extend their dwelling at a later date according to available means and assistance. Techniques: The traditional timber frame structure is strengthened to better resist earthquakes and hurricanes and the walls filled in with locally available materials. Four different kinds of infill are possible, depending on what is locally available: straw-clay on a lath of battens or wattle, brickwork made of self-produced earth blocks or stone blocks in earth mortar.

Fig. 490 Different development options

(architect: Alix Hubert, redrawn) Fig. 491 After the earthquake: the skeleton frame and roof remain standing and the residents survived. Only the stone walls collapsed.

284 Light Earth Building

Fig. 492 The light blue straw-clay house

Fig. 493 The green house

Fig. 494 The pink house

Fig. 495 Variant with earth brick infill

Fig. 496 Variant with straw-clay on wattle

Projects  285 

25

Schap 2011 – Primary school in South Africa (ZA)

Johannesburg, South Africa, 2011 Architect: The design was developed as part of a project at the FH Kärnten, Austria Consulting: Professor Peter Nigst with students Jürgen Wirnsberger and Elias Rubin Technique: Straw light earth in shuttering Earth building works: Undertaken as part of a practical experience project by the FH Kärnten and local labourers The loadbearing structure is a hybrid construction of columns made of locally-made prefabricated concrete elements and steel beams with a light earth wall infill plastered on both sides with fibre-reinforced earth/lime plaster.

Fig. 497 Floor plan (after a drawing by the Schap team)

Fig. 498 Light earth wall infill

between concrete posts

286 Light Earth Building

Fig. 499 Courtyard Fig. 500 Classroom Fig. 501 Exterior view Fig. 502 Building shell

Projects  287 

26

Single-family home in Victoria (AU)

Daylesford, Victoria, Australia, 2011 Architects: Vasko Drogiski, Hepburn Building Design & Land Planning Consulting: James Henderson, Henderson Clayworks Technique: Straw light earth in shuttering Earth building works: Henderson Clayworks / Hepburn Building Design & Land Planning A 19 cm wide frame holds the light earth walling with 35 mm external lime render and 25 mm earth plaster on the inside resulting in a total wall thickness of 25 cm, which is common for the temperate climate in Victoria, and makes it possible to use standard window and door elements. James Henderson developed a custom tumbler for mixing the material for the walls and plaster, which comprises a mixture of wheat straw and locally-sourced earth. The façades are coated with three layers of lime and sand render applied with a pump and the internal faces with a 20 mm straw-clay undercoat plaster and 5 mm earth-sand fine-finish topcoat. See also figure 38.

Fig. 503 Wall section (architect: Vasko Drogiski, redrawn) Fig. 504 Temporary sprouting of the walls during drying

288 Light Earth Building

Fig. 505 Exterior view of lime-rendered building Fig. 506 Floor plan (architect: Vasko Drogiski, redrawn)

Fig. 508 The tumbler discharges Fig. 507 Tumbler

directly into a wheelbarrow

Projects  289 

27

Private house in Darmstadt (D)

Darmstadt, 2012 (April to October) Architects: Schauer + Volhard, Darmstadt Earth building works: Harry Unger GmbH, Heppenheim Techniques: Light earth, manually applied, stacked earth walls The structure is a prefabricated timber panel construction with an external skin of heavy light earth applied to a framework of continuous horizontal laths (see fig. 157). Once dried, the internal faces were clad with gypsum fibreboard and the cavity filled with blow-in cellulose insulation. The internal walls are clad on one side with gypsum fibreboard and filled with stacked heavy earth bricks. The floors are made of solid laminated timber elements and the rafter roof insulated with blow-in cellulose insulation. The façades are plastered with lime render and painted with silicate paint. The external skin of heavy light earth (weighing 25 tonnes) buffers temperature differences and retains the heat of the sun, increasing the structure’s temperature in the winter months. The internal insulation ensures the internal wall surfaces remain warm at lower ambient air temperatures, reducing the degree of ventilation heat loss. The timber structure has a total thermal mass of 35 tonnes in the floors and internal walls, ensuring it remains pleasantly cool in summer. See also figures 74, 89, 156–159, 242. Fig. 509 Section

Fig. 510 Floor plans

290 Light Earth Building

Fig. 511 View of the garden façade from the south west

Fig. 512 Continuous external straw light earth skin

Fig. 513 Two-storey gallery space over the dining area

Projects  291 

Fig. 514 Section through façade

1 External wall Timber panel wall construction, stiffened with gypsum fibreboard on the internal face, cellulose insulation on the interior, light earth, 1,000 kg/m³, manually applied onto laths on the exterior face. External lime render. t = 29 cm, U = 0.24 W/m²K, Q = 190 kJ/m²K

4

1

2

1 3

2 Internal wall Timber panel wall construction, lined on both faces with gypsum fibreboard, dry stacked wall infill with extruded earth bricks, 1,800 kg/m³. 3 Floor Parquet flooring, floating screed, glulam floor, gypsum fibreboard mounted on supporting battens 4 Roof Gypsum fibreboard mounted on supporting battens, cellulose insulation between rafters, sheathing, fibre-cement roof covering

Fig. 516 External walls, 12 cm light earth, internal Fig. 515 Erection of timber panel elements

292 Light Earth Building

walls with stacked earth bricks

Fig. 517 Continuous application of light earth on battens under the already complete roof with larch wood window jambs already in place

Fig. 518 Corner detail showing the battens of the

light earth skin

Fig. 519 View from the south

Projects  293 

28

Single-family home in Kaipara Flats (NZ)

Kaipara Flats, New Zealand, 2013 Architects: Florian Primbs, nzeb design Ltd Consulting: RPH Consulting Ltd Technique: Woodchip light earth in shuttering Building works: Timber frame – Richard Willcock Builder Ltd; Earth building – undertaken by the client under instruction from the architect Composition of the light earth mix: earth, mostly from the site, cypress wood shavings (macrocarpa) and pumice (approx. 750 kg/m³). The structure is a lightweight single-stud timber frame with rebated studs and corresponding sliding horizontal laths to hold the wall infill in place. Corrugated metal sheeting was used as formwork. The external render is comprised of two undercoats of earth plaster with wood shavings and coarse sand with hessian mesh reinforcement, and a two-layer topcoat lime render, painted with silicate paint. The internal plaster is the same undercoat plaster and hessian reinforcement as the external render but with a topcoat of earth plaster smoothed with a sponged float. The cold face (south side) and the shaded west side were given an additional layer of insulation with ventilated board and batten siding.

Fig. 520 Floor plan (architect: Florian Primbs, redrawn) Fig. 521 Hallway

294 Light Earth Building

Fig. 522 View from the north west Fig. 523 Construction principle (architect: Florian Primbs, redrawn)

Fig. 524 North bedroom

Fig. 525 Timber frame

Projects  295 

Appendix Sources and reference literature

[Anger/Fontaine 2009] Anger, Romain; Fontaine, Laetitia: Bâtir en terre. Du grain de sable à l’architecture. Éditions Belin / Cité des sciences et de l’industrie, Paris 2009 [Arch+ 1985]  Arch+ 80: Lust auf Lehm. Klenckes Verlag, Aachen 1985 [architektur 6/1997] Architektur, Österreichisches Fachmagazin, Laser Zeitschriftenverlag, Vienna 1997 [ausschreiben.de] Specification texts on earth building (in German). In: www.ausschreiben.de [Baier 1985] Baier, Bernd; Wulf, Michael: Der neue Lehmbau. Bedürfnis oder Interesse? arcus, Vol. 5, Institut für internationale Architektur-Dokumentation, Munich 1985, pp. 214–219 [Bardou/Arzoumanian 1978]  Bardou, Patrick; Arzoumanian, Varoujan: Archi de Terre. Éditions parenthèses, Marseille 1978 [Becker 2008] Becker, Jürgen: Erdbebensicheres Bauen mit Kokosfaser Lehm. Earthquake resistant construction using coconut fibre reinforced earth. In: [Lehm 2008], pp. 136–142 [Beidatsch 1946]  Beidatsch, Alfred: Wohnhäuser aus Lehm. Berlin, Buxtehude 1946 [Bobran 1967]  Bobran, H.W.: Schallschutz, Raumakustik, Wärmeschutz, Feuchtigkeitsschutz. Ullstein Verlag, Berlin Frankfurt Vienna 1967 [Bodelschwingh 1925] Bodelschwingh, Gustav von: Ein alter Baumeister und was wir von ihm gelernt haben. Verein “Heimstätte” Dünne (Ed.) Dünne, approx. 1925; New edition Heimstätte Dünne, 1990 [Börjesson 1997] Börjesson, Sven: Grundlagen zur Optimierung der Anwendung von Lehmbauprodukten. Diploma thesis Fachhochschule Leipzig 1997 [Bruckner 1996] Bruckner, A.: Bauen mit Lehm – anhand von Beispielen aus Österreich, Deutschland und Südtirol. Diploma thesis TU Vienna 1996 [Bühring 2000] Bühring, D.: Industrielle Fertigung von Hanf-Lehmsteinen. In: [Lehm 2000], pp. 30–37 [Bundesverband GBW 1990] Bundesverband Gesundes Bauen und Wohnen GBW (Ed.): Zeitschrift Gesundes Bauen und Wohnen; Vol. 40, Schwerpunkt Lehmbau; Braunschweig 1990 [Cointeraux 1793] Cointeraux, François: Schule der Landbaukunst. Hildburghausen 1793 [CRAterre 1979, 1983]  CRAterre – Centre de Recherche et d’Application Terre: Construire en Terre. Éditions alternatives, Paris 1979, 1983 [CRAterre 1986] CRAterre: Identification et Critères de Sélection des Terres. Approche scientifique et technique du matériau terre. CSTB/CRAterre, Paris/Eybens 1986 [CRAterre 1989] CRAterre-Houben, H.; Guillaud, H. : Traité de Construction en Terre. Éditions parenthèses, Marseille 1989 [CRAterre 2008] CRAterre (Ed.): Terra incognita – discovering and preserving European earthen architecture. Argumentum / Culture Lab Editions, Lisbon 2008 [CRAterre-EAG 1994] CRAterre-EAG; Houben, Hugo / Guillaud, Hubert: Earth Construction. A comprehensive guide. Intermediate Technology Publications, London 1994 [CSTB 1984] CSTB – Centre Scientifique et Technique du Bâtiment: Caractérisation Thermique d’un Mélange Terre Paille. Grenoble 1984 [CSTB et al. 2011] CSTB; CRAterre; ENTPE-Formequip; Construire en Chanvre; Réseau Ecobâtir; CAPEB; Avec la collaboration de la FFB: Analyse des caractéristiques des systèmes constructifs non industrialisés. Extrait du rapport final pour diffusion, 2011, p. 22 [Dachverband Lehm 2009] See: [Lehmbau Regeln 1999, 2009] [Dachverband Lehm] Homepage of the Dachverband Lehm e.V. Weimar including information for consumers, technical datasheets, current information, addresses of specialists, information on vocational training and realised projects: www.dachverband-lehm.de [Dahlhaus/Kortlepel 2004] Dahlhaus, Ulrich; Kortlepel, Uwe; et al.: Lehmbau 2004 – aktuelles Planungshandbuch für den Lehmbau. Manudom-Verlag, Aachen 1997, 2001 and 2004 [Dethier 1981] Dethier, Jean: Des Architectures de Terre. Éditions du Centre Georges Pompidou, Paris 1981, 1986 [Dethier 1982]  Dethier, Jean (Ed.): Lehmarchitektur – Die Zukunft einer vergessenen Bautradition. Prestel Verlag, Munich 1982 [Dewulf 2007] Dewulf, Michel: Le torchis, mode d’emploi. Éditions Eyrolles, Paris 2007 [DIBt 2014] Deutsches Institut für Bautechnik (www.dibt.de): Musterliste der Technischen B ­ aubestimmungen 2014 [Dilthey 1982] Dilthey, Andreas; Speidel, Manfred et al.: & zwar mit Lehm. Experimente mit Lehm 1979–82. Exhibition catalogue RWTH Aachen, 1982 [Dilthey 1985]  Dilthey, Andreas: Leichtlehmkappendecken. In: [Minke 1984–1987] Vol. 1 1984, pp. 30–32 [DIN 1169 1947] DIN 1169: Lehmmörtel für Mauerwerk und Putz, 1947. Reprinted in: [Dahlhaus/Kortlepel 2004] [Sieber 1994]

296 Light Earth Building

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Eine Einführung in Experimenten; Vols. 1–3. Bauverlag Wiesbaden Berlin 1986, 1989, 1992 [Steinmann 1994] Steinmann, Nadia: Lehm für die Siedlung. Die Lehmbausiedlung “Via Felsenau". In: Hochparterre Vol. 5/1994, pp. 30–31, CH-Glattbrugg 1994 [Tonadur 1949] Tonadur. Eine neuzeitliche Lehmbauweise, Naturbauweisen Vol. 8/9 1949, pp. 135 (author unknown) [Vanros 1981]  Vanros, Guy : Studie van bouwfysische Kenmerken van Lemen Vakwerkwanden. Final thesis at the Catholic University of Leuven, Belgium, 1981 [Vick 1949] Vick, Friedrich: Amerikanischer Lehmbau. Bauen und Wohnen 1949, p. 315 [Volhard 1982]  Volhard, Franz: Bauen mit Lehm. In: Arch+ 62; Klenckes Verlag Aachen 1982, pp. 32–33 [Volhard 1983] Volhard, Franz: Leichtlehmbau. Alter Baustoff – neue Technik. C.F. Müller Verlag Karlsruhe 1983 [Volhard 1985]  Volhard, Franz: Anwendung von Leichtlehm im Holzskelettbau und der Fachwerk­sanierung. In: [Minke 1984–1987] Vol. 3 1985, pp. 11–31 [Volhard 1990] Volhard, Franz: Leichtlehm, Zuschläge im Vergleich. In: [Bundesverband GBW 90] 1990, pp. 13–17 [Volhard 1992] Volhard, Franz: Gotisches Haus Römer 2–6 in Limburg. Untersuchung der Strohlehmausfachungen und Lehmputze, gekürzte Fassung. In: Forschungen zur Altstadt, published by Limburg Town Council, 1992, pp. 212–224 [Volhard 1995] Volhard, Franz: Lehmbaustoffe. In: Häfele; Oed; Sambeth (Ed.): Ökologische Baustoffe. Wasmuth Verlag, Stuttgart 1995, pp. 108–125 [Volhard 1997] Volhard, Franz: Fachwerk. Lehmbaustoffe im Holzbau. In: [architektur 6/1997], pp. 64–66 [Volhard 1998] Volhard, Franz: Mit Lehm bauen. In: detail 1/98, Institut für Internationale Architekturdokumentation, Munich 1998, pp. 77–82 [Volhard 1998] Volhard, Franz: Wohnhausbau mit Lehm – Aktuelle Beispiele. In: Modern Bauen mit Lehm, Overall Verlag Berlin 1998, pp. 105–116 [Volhard 2000] Volhard, Franz: Erfahrungen mit den Lehmbau Regeln. In: [Lehm 2000], pp. 140–145 [Volhard 2010a] Volhard, Franz: Lehmausfachungen und Lehmputze – Untersuchungen historischer Strohlehme. Fraunhofer IRB Verlag, Stuttgart 2010 [Volhard 2010b] Volhard, Franz: Lehm – feucht oder trocken? Lehmbaustoffe und Raumklima. In: Pilz, Achim (Ed.): Lehm im Innenraum. Fraunhofer IRB Verlag, Stuttgart 2010, pp. 29–36 [Volhard 2010c] Volhard, Franz: Lehmsichtigkeit im Innenraum in der Historie – historische Lehm- und Kalkputze. In: Pilz, Achim (Ed.): Lehm im Innenraum. Fraunhofer IRB Verlag, Stuttgart 2010, pp. 74–78 [Volhard 2011] Volhard, Franz: Untersuchungen historischer Ausfachungs- und Putztechnik. In: Bausubstanz Vol. 2, Fraunhofer IRB Verlag, Stuttgart 2011, pp. 31–35 [Volhard 2012] Volhard, Franz: Clay-straw as an external shell in timber construction. In: [Lehm 2012], pp. 296–299 [Volhard 2016] Volhard, Franz: Construire en Terre Allégée (Bauen mit Leichtlehm, French edition). Actes Sud, Arles 2016 [Volhard/Westermarck 1994] Volhard, Franz; Westermarck, Michael: Savirakentaminen. kevytsavitekniikka (Leichtlehmbau, Finnish edition). RAK Rakennusalan kustantajat, Helsinki 1994 [Wagner 1947] Wagner, Wilhelm: Anleitung zur Untersuchung und Beurteilung von Baulehmen. Hessischer Lehmbaudienst Wiesbaden-Dotzheim (Ed.), Wiesbaden 1947 [Weiss 1972]  Weiss, Gustav: Freude an Keramik. Ullstein Verlag Frankfurt Berlin Vienna 1972 [Wiechmann 1986] Wiechmann, Horst, Institut für Bodenkunde der Universität Bonn: Eigenschaften des Lehmanteils in Fachwerken. In: [Kommern 1986], pp. 63–72 [Wimpf 1841] Wimpf, W.J.: Der Pisébau oder die vollständige Anweisung äusserst wohlfeile, dauerhafte, warme und feuerfeste Wohnungen aus blosser gestampfter Erde, zu erbauen. Classische Buchhandlung, Heilbronn 1841 [WTA 2002] WTA (Wissenschaftlich-Technische Arbeitsgemeinschaft für Bauwerkserhaltung und Denkmalpflege e.V.) (Ed.): Fachwerkinstandsetzung nach WTA. Vol. 2 Aktuelle Berichte; Fraunhofer IRB Verlag, Stuttgart 2002 [Ziegert 2003] Ziegert, Christof: In Balance, Das Feuchtesorptionsvermögen von Lehmbaustoffen. In: db deutsche bauzeitung 2/03, Deutsche Verlags Anstalt, Stuttgart 2003, pp. 73–80 [Zogler 2004] Zogler, Oliver: Wohnhäuser aus Lehm – Neubauten und Renovierungen. Deutsche Verlags Anstalt DVA, Munich 2004 [Zur Nieden/Ziegert 2002] Zur Nieden, Günter; Ziegert, Christof: Neue Lehmhäuser international; Projektbeispiele, Konstruktion, Details. Bauwerk Verlag, Berlin 2002

300 Light Earth Building

Publications of projects

1 Conversion and extension of a half-timbered house (D) 1980 House L, Groß Gerau. In: [FAL 2015], pp. 12–13 Förderpreis des BDA Bund Deutscher Architekten (Ed.): Um uns herum – Architekten gestalten ihre Umwelt. Exhibition catalogue. Verlag der Georg Büchner Buchhandlung, Darmstadt 1985, pp. 44–45 Volhard, Franz: Leichtlehmbauweise. Um- und Anbau eines Wohnhauses. In: Deutsche ­Bau­zeitung Vol. 2 1982, pp. 40–42 2 New private house with workshop (D) 1984 House S, Darmstadt. In: [FAL 2015], pp. 14–15 Schauer, Ute: Ein einfaches Haus. In: Der Architekt 1/89; Architektur mit kleinem a – Vom gewöhnlichen Bauen. Bund Deutscher Architekten BDA (Ed.); Forum Verlag, Stuttgart 1989, pp. 29–31 Volhard, Franz; Schauer, Ute: Wohnhaus mit Nebengebäude in Leichtlehmbauweise in ­Darmstadt. In: [Arch+ 1985], pp. 40–42 3 Earth building settlement: Domaine de la Terre, L’Isle d’Abeau (F) Lozach’Meur, Adeline; Tirard, Jean-Chrisophe; Dethier, Jean: L’isle d’Abeau – ville nouvelle. Maisons de terre, présentation des projets, 1984 Serwe, Hans-Jürgen: Die experimentelle Lehmbausiedlung L’Isle d’Abeau. In: [Arch+ 1985], pp. 28–31 5 Barn conversion (D) Renovation of a Barn, Offenbach. In: [FAL 2015], pp. 36–37 Umbau einer Scheune in Offenbach. In: detail 6/1997, Institut für Internationale Architektur­dokumentation, Munich 1997, pp. 892–895 6 House extension (D) Architektenkammer Hessen (Ed.): Wohn-Häuser. Auszeichnung vorbildlicher Bauten Hessen. Junius Verlag, Hamburg 1994, pp. 35–42 House B, Darmstadt. In: [FAL 2015], pp. 42–43 Lehm im Quadrat. Wohnhausanbau. In: [Zur Nieden/Ziegert 2002], pp. 104–109 Praktisch und ökologisch. Wohnhaus in Darmstadt. In: [architektur 6/1997], pp. 71–73 Wohnhausanbau in Darmstadt. In: Das Bauzentrum 4/93; Auszeichnung vorbildlicher Bauten Hessen 1993. Verlag das Beispiel, Darmstadt 1993, pp. 112–113 7 Cowshed and barn conversions (F) Delabie, Christian: Briques de terre crue et Terre Paille en Basse-Normandie. Association Régionale Biomasse Normandie, Caen 1987 Delabie, Christian: Construire des bâtiments d’élevage en terre-paille. Energie Verte 4/87, Association Régionale Biomasse Normandie 1987 8 Summerhouse (S) Ferienhaus; Sverre Fehn. In: md moebel interior design. Sonderveröffentlichung Wohnen; Konradin-Verlag Robert Kohlhammer, Leinfelden-Echterdingen 1995, pp. 116–120 Lundsten, Bengt; Achcar, Leticia; Westermarck, Mikael: Selvitys savirakentamisesta. Raporti. Teknillinen korkekoulu, Helsinki 1992. ISBN 951-22-1315-x Summer Cottage, Mauritzberg, Schweden. In: [Gaia Architects 2003], pp. 180–181 Summer house, Sverre Fehn. In: Award Winning Architecture; International Yearbook, Munich, New York 1997 pp. 34–37 The Eco House. In: [Rael 2009], pp. 122–125 9 Atelier (D) Abgehoben. Atelierhaus. In: [Zur Nieden/Ziegert 2002], pp. 64–71 Atelier einer Bildhauerin. In: [Zogler 2004], pp. 16–21 Studiohouse, Darmstadt. In: [FAL 2015], pp. 44–45 Atelierhaus. In: Holzbauatlas. Institut für Internationale Architektur-Dokumentation (Ed.); edition detail, Munich 2003, pp. 321 Bildhaueratelier Darmstadt. In: Große Häuser, kleine Häuser. Ausgezeichnete Architektur in Hessen 1998; Bund Deutscher Architekten BDA im Lande Hessen e.V. (Ed.), pp. 26–27 Bildhauer-Atelier in Darmstadt. In: detail 2/1997. Institut für Internationale Architekturdokumentation, München 1997, pp. 178–182 Freiraum für die Kunst. Bildhaueratelier in Darmstadt. In: [architektur 6/1997], pp. 67–70 Krön, Elisabeth: Atelierhaus in Darmstadt. In: baumeister und Baumeister Werkplan 1/98, Callwey Verlag, Munich 1998, pp. 22–25 Pfeifer, Matthias; Zeitter, Helmut; Volhard, Franz: Die Ideenkiste. In: mikado 4/96; Magazin für Holzbau und Ausbau. Weka Verlage mikado, Augsburg 1996, pp. 33–36

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10 Earth house in Maria Rain (A) Architektenhaus in Lehmbauweise. In: [Zogler 2004], pp. 64–67 Architektur antwortet – im Werk von Eva Rubin. FH Kärnten, Studiengang Architektur (Ed.); Nigst, Peter et al.; archimap publishers, Berlin 2010 11 Historical renovation and extension of a listed building (D) Haus Eilberg und Haus Schneiker. In: Architektenkammer Hessen (Ed.): Bauen im Bestand. Vorbildliche Bauten in Hessen. Junius Verlag, Hamburg 2000, pp. 30–41 Sanierung zweier barocker Fachwerkhäuser. In: [Zogler 2004], pp. 22–27 Two Half-Timbered Houses, Mörfelden. In: [FAL 2015], pp. 32–35 12 Historical renovation of a listed building (D) See previous project 13 Single-family home in Raisio (FIN) Private House, Raisio, Finland. In: [Gaia Architects 2003], pp. 188–189 Salonen, Minna: Light Straw Clay Block structures in construction. Experimental house in the housing fair in Raisio. Turku Polytechnic, Environment and Civil Engineering, Turku 2001 Wohnhaus in Turku. In: [Minke 2009], pp. 168–169 14 Littlecroft, demonstration building for a research project (UK) Littlecroft, Private House extension. In: [Gaia Architects 2003], pp. 155–170 and pp. 172–173 15 Sandberghof community-oriented housing Becker, Anette; Kienbaum, Laura; et al. (Ed.): Umbau Sandberghof, Darmstadt. In: Bauen und Wohnen in Gemeinschaft – Building and Living in Communities; DAM Deutsches Architekturmuseum Frankfurt; Birkhäuser, Basel 2015, pp. 140–145 Kottjé, Johannes: Durchdacht bis ins kleinste Detail. Barocke Hofanlage in Darmstadt. In: Attraktiv Wohnen in denkmalgeschützten Häusern. Deutsche Verlags-Anstalt, Munich 2015, pp. 36–49 Pilz, Achim: Sanierung Sandberghof, Darmstadt – Schauer + Volhard. In: [Lehm im Innenraum 2010], pp. 202–208 Sandberghof – Gemeinsam Wohnen im Alter. In: Architektenkammer Hessen (Ed.): Einsparhaus. ­Energie­effiziente Architektur. Vorbildliche Bauten in Hessen. Jovis Verlag, Berlin 2009, pp. 156–159 Sandberghof, Darmstadt – Living Together in Maturity. In: [FAL 2015], pp. 30–31 Sandberghof. In: BDA Bund Deutscher Architekten (Ed.): Große Häuser, kleine Häuser. Ausstellungskatalog. Ausgezeichnete Häuser in Hessen. Frankfurt 2008, pp. 22–23 Volhard, Franz: Sandberghof – Umbau eines Fachwerkhauses. In: Wohnung + Gesundheit Vol. 133; Institut für Baubiologie + Oekologie Neubeuern IBN (Ed.); Neubeuern 2009, pp. 10–12 Volhard, Franz: Sandberghof – conversion and renovation using earthen building materials. In: [Lehm 2008], pp. 170–179 Volhard, Franz: Wohnprojekt Gemeinsames Wohnen im Alter – Umbau eines denkmalge­schützten Fach­werk­ hauses von 1758. In: Holzbau – die neue Quadriga Vol. 5/2009. Verlag Kastner, Wolnzach 2009, pp. 41–45 17 Church in Järna (S) Community Church, Järna, Schweden. In: [Gaia Architects 2003], pp. 178–179 18 Guesthouse in New Mexico (USA) Handcrafted Efficiency. In: [Econest 2005], pp. 104–109 19 Prajna Yoga Studio in New Mexico (USA) Prajna Studio, Santa Fe, New Mexico. In: [Econest Home 2015], pp. 249–255 21 Single-family home in Carla Bayle (F) CEREMA du Sud-Ouest, Suivi in situ du comportement hygrothermique d’une maison en ­terre-paille, rapport final, mars 2013. Marcom, Alain: Construire en terre paille. Éditions Terre vivante, Mens 2011 22 Twenty houses made of straw light earth (F) Le Hameau des Buis, utopie réalisée, La Maison écologique, n° 59/2010, pp. 40-42 23 Conversion of a rural house in Normandy (F) Réhabilitation en Calvados. In: Presse locale (Ouest France), site internet ARPE BN 24 House rebuilding in Haiti Reconstruire Haïti. Après le séisme de janvier 2010. CRAterre-Ensag, Grenoble 2014 25 Schap 2011 – Primary school in South Africa (ZA) Schap! school and production. In: [Schap 2011] 27 Private house in Darmstadt (D) Brüggemann, Michael: Natürliche Schönheit, Einfamilienhaus J in Darmstadt. In: DBZ Deutsche Bauzeitschrift 6/2014, pp. 58–65 Einfamilienhaus, ökologische Bauweise. In: Objektdaten Neubau N13, BKI Baukosteninfor­ma­tionszentrum Deutscher Architektenkammern, Stuttgart 2015, pp. 516–520 Exemplarisch ökologisch. In: Architektenkammer Hessen (Ed.): Vorbildliche Bauten in Hessen, 2015 House J, Darmstadt. In: [FAL 2015], pp. 46–47

302 Light Earth Building

Haus J. In: Große Häuser, kleine Häuser. Ausgezeichnete Architektur in Hessen 2008–2013; Bund Deutscher Architekten BDA im Lande Hessen e.V. (Ed.), pp. 56–57 Pilz, Achim: Handwerkliche Fassade mit Lehm. In: ausbau + fassade 4/2014 pp. 24–25 and 9/2014, pp. 50–51, Bundesverband Ausbau und Fassade Pilz, Achim: Neubau mit Innendämmung – Stroh und Lehm als Partner. In: Wohnung + Gesundheit Nr. 150, Institut f. Baubiologie Neubeuern 2014, pp. 40–42 Pilz, Achim: Wärmespeichernde Lehmschale. In: applica, die Zeitschrift für das Maler- und Gipsergewerbe 10/2013, pp. 16–18 See [Volhard 2012] Ulmer, Andrea: Gutes Klima. In: Genußraum – das Magazin für Wohnen und Geniessen 1/2014, Munich 2014, pp. 52–55 Vetter, Andreas: Haus J – Reiz des Nachhaltigen. In: Traumhaft schöne Einfamilienhäuser um 250.000 Euro. Callwey Verlag, Munich 2014, pp. 32–35

Appendix  303 

Index

Abrasion 179, 181 Additional insulation 39, 75, 81, 107, 119f, 202, 209 Additives 65 Adhesion of plaster 22, 180, 181f Adhesive strength 182 Adobe 12 Aggregates 42, 53, 66, 188 Agitators 60, 190 Air temperature 38, 206, 208 Airborne moisture 210, 213f Airborne sound insulation 227, 231 Airtightness 156, 160ff, 184, 202, 219f, 232 Amplitude damping effect 209 Anchoring methods 186 Application classes 133, 150, 216 Artificial drying 37, 187, 221 Atterberg test 51

Compressed blocks 12, 139 Compressive strength 32, 133 Compressive strength of mortar 180 Condensation 218f Conserving effect 162 Consistency 12, 44, 171 Consistency limits 51 Consistency of the clay slip 62ff, 71, 77 Construction moisture 220 Construction period 32, 187 Construction permits 195 Construction supervision 197 Construction time 37 Constructional wood preservation 163 Corner profiles 168 Costs 32, 40, 134, 187f Cracks 42, 66, 163, 165, 169, 180

Bale straw 53, 66, 99, 112, 175 Ball dropping test 45 Ball forming test 45 Bamboo 99, 274 Battens 33, 94, 102, 111ff, 117, 120, see also Laths, Stakes Binding agent clay 171 Binding force see Cohesion Blocks see Light earth blocks Brick and block formats 133f Bricks 148ff, 154, 187, 189, 195, 216, see also Light earth blocks Building boards 136, 158, 189 Building codes see Regulations Building contractors 26, 29, 188, 190f, 197 Building material class 221 Building restoration 124, 190 Bulk density 33, 37, 75f, 98, 180, 197, 199, 203, 206, 232

Damp proof membranes 159 Damp proofing 184, 215 Daub see Wattle and daub Decomposition 198, 221 Dew point 131, 218f DIN 4108 196, 200, 210 Dipping method 71 Doors 182 Driving rain protection 160, 163, 187, 215 Dry construction 133, 142, 154, 187, 216 Dry lining boards 133, 136, 154, 258 Dry mixtures 80 Drying 165, 187, 198, 209, 215, 220 Drying blocks 141 Drying conditions 54, 179 Drying earth 58 Drying problems 129 Drying properties 39, 209, 214, 219 Drying protocol 187 Drying time 32, 37, 64, 81, 94, 141, 187, 220 Dung 66, 177 Durability 209, 211

Capillary conduction 39, 124, 131, 156, 214f, 219 Casein 173 Ceilings 107, 158, 187, 230 Cladding 82, 135, 158ff, 164, 198, 208 Clay 11, 43, 45, 50 Clay slip 43, 51, 57f, 62ff, 69ff, 75, 79, 198, 220 Clay-based paints 179 Clay-rich earth see Rich earth Climate zone 11, 13, 36, 208, 278, 288 Clumps 51, 57f Coating with clay slip 128f, 163 Coatings 11, 169, 173 Cob 12, 33 Cohesion 41, 43f, 51f, 198 Cohesion test 45 Cohesion test of the fine soil fraction 51 Coloured plasters 179 Comb 124, 176 Compacted earth floors 113, 234 Compaction 96, 199

304 Light Earth Building

Earth 41, 57, 78 Earth building products 26, 29, 133, 188ff, 193, 197 Earth content 66, 75f, 98, 203 Earth masonry 12, 18, 33 Earth mortars 169, 180ff, 189, 195 Earth pigments 163, 169, 173 Earth plasters 66, 148, 163, 169, 171f, 174, 178f, 180f, 189, 195, 213 Earth reels 103, 111f, 120, 244, 258, 261, 268 Earth screed 184 Earth testing methods see Soil identification Earthquake stability 14 Electrostatic charging 214 Elevator 78 Equilibrium moisture 39, 43, 162, 210, 214 Erosion, through water 53 Errors see Mistakes

Excavation material 52 Expanded glass, clay 56 Exposed timber 82, 98f, 145, 160ff, 227 External renders 159f, 163, 176 External thermal insulation 160 External walls 39, 81f, 86, 127f, 133, 201, 206, 209, 230 Extruded earth bricks 150, 216

Insulation 33, 36, 38f, 75, 93f, 128ff, 199ff, 206ff Intermediate floor 116, 154, 231 Internal insulation 131, 218 Internal plaster 164, 174 Internal wall linings 75, 93, 122, 127ff, 135, 145, 148, 154f, 234, 244, 261 Internal walls 75, 81, 86, 106, 133, 135, 150, 154f, 158, 206, 229

Façade cladding 160 Fibre-clay 33, 44, 69, 99, 100, 116, 124, 135, 168 Fibre-clay plaster 165, 174, 177, 208 Fibre-reinforced lime plaster 177 Fibre-reinforcement see Stabilisation with fibres Fibres 53 Fine fibres 33, 66, 172 Fine soil fraction 51 Fire protection 202, 221 Fire resistance class 225f Fire safety class 221 Fire-resistance 39, 75, 116 Firewalls 229 Fixings 186 Flammability 225 Float 96, 99, 131, 175 Floor covering 231 Floor infill 116f Floor slabs 151 Floors 107, 151, 183, 226, 230 Formwork 53, 81f, 87, 90, 96, 188 Formwork, lost 81, 93, 120, 154 Formwork, permanent 54, 116, 120 Formwork, sliding 81, 113, 120, 127, 129 Frame construction 13 Free-fall mixers 178 Frost 37, 53, 57, 169, 187, 199, 215

Japanese trowels 171, 177 Joins 145, 148, 154, 160 Joints 160, 165, 229

Gaps 83, 96, 124, 165, see also Joins / Joints Geotechnical classification 50 Gypsum plasters 179 Gypsum-fibreboard 184 Hair-reinforced lime render 19, 145, 150, 163, 165f, 168, 174 Half-timber constructions 13, 16, 19, 26, 82, 93, 99, 124, 145, 160, 190, 226 Hand-operated press 139 Hay 53, 71, 112, 117, 172 Heat absorption 208 Heat transfer coefficient– U see U-value Heating panels 136, 156 Heavy mixtures 75, 77, 98, 106f Hemp 53 Hessian 162, 166 Historic monuments 196 Humidity exposure tests 214 Hygroscopic moisture 213 Hygroscopicity 180, 210, 214 Impact sound insulation 230f Installations, electrical 38, 148, 186f, 219 Installations, sanitary 184, 186

Labour 188 Ladder studs 83, 249, 274 Laser diffraction 50 Lath floor 117 Laths 104, 117ff, 131 Lathwork 106, 120, 131 Latticework 94, 99 Lean earth 18, 41ff, 51, 63, 76, 174, 180, 198 Lean mortars 179 Lehmbau Regeln 29, 133, 179, 193, see also Norms Length of straw 53, 66, 203 Light earth 36, 127, 194 Light earth blocks 75, 129, 133ff, 139, 189, 202 Light earth masonry 81, 133, 142 Light earth mortar 145, 174, 179 Light earth panels 63, 135 Light earth plasters 175 Lightweight mixtures 75ff, 95, see also Very lightweight mixtures Lime addition 65 Lime mortar 165, 173, 178f Lime plaster bond 19, 124, 176 Lime plasters 163, 179 Lime renders 168, 176 Lime wash 173, 177f Linseed oil 163, 173, 234 Liquifying agents 64, 76, 184, 220 Loadbearing framework 82 Loess soil 18, 43, 174, 179 Machine-processing straw-based light earth see Tumbler mixer Malleable 33, 37, 41, 71, 98, 106f Manual application 54, 98, 106, 119, 122, 131, 290 Manual manufacture of blocks and panels 136 Manure 177 Masonry infill panels 145 Masonry mortar 142, 179, 189, 194 Mastic seam sealant 165 Methylene Blue Test 51 Mineral aggregates 53, 56, 73, 203 Mineral light earth 37, 81 Minimum thermal resistance 201, 218 Mistakes 40, 198 Mixers 60, 69, 73, 78, 190, see also Tumbler mixer Mixing 69 Mixing floor 78 Mixing proportion 38, 75, 171, 199 Mixing water 42, 76ff

Appendix  305 

Moisture content 210f Moisture exposition 215 Moisture proofing 159 Moisture regulation 180, 214, 218 Moisture transport 131, 214 Mould formation 65, 179, 187, 218, 220 Moulds 12, 136, 141, 150f, 197 Norms 22ff, 29, 31, 192ff, 221 Norms, preliminary 22, 192 Notches 102, 109, 117, 145 Offcut material see Rest material Organisation 78, 188, 197 Paints 163, 178 Panel elements 135 Panel infill 124, 127, 145 Panel products 22, 135, 189 Panels in half timber construction 33, 98f, 124, 127, 136, 145 Particle size distribution 44, 50f Partitioning walls see Internal walls Party walls 229 Perforated bricks 216 Perlite 56 Pisé construction 17, see also Rammed earth Plank studs 83, 86 Planning permission 195 Plaster base see Plaster substrate Plaster lath ceiling 117 Plaster laths 106, 131 Plaster mortar 133, 171, 174, 178f, 182, 189, 192, 194 Plaster substrate 93, 129, 163, 165, 175 Plastered timber elements 165, 175 Plastering machines 60, 69, 79, 131, 172, 178, 236 Plasters 163, see also Earth plasters Plasticity index 51 Plugs 186 Pores 210, 213f Practical moisture content 211, 220 Prefabricated products see Earth building products Prefabrication 45, 86, 188, 192 Preparatory work 190 Preparing the earth 57 Preparing the straw 66 Presses 12, 139 Processing of earth 42 Proof of fitness for purpose 193 Proportion of earth see Earth content Proportion of straw see Straw content Pulverised clay 52, 65 Pumice 56 Pumps 60, 69, 78, 191 Rainwater 215 Rammed earth 12, 17, 33, 37, 174, 188, 190, 196 Rationalisation 20, 188ff Ready-made material 32, 80, 190 Ready-made products see Earth building products Ready-mix mortars 178, 189 Recycling 133

306 Light Earth Building

Recycling straw clay panels 127 Reed boards 81, 94, 116 Reed plaster lath 54, 93, 119, 165 Regulations 29, 192, 195, see also Norms Reinforcement mesh 150, 154, 156, 172, 175, 184 Relative humidity 213f Repairing loose stakes 124 Repairing straw-clay panels 124 Rest material 38, 133, 188 Retention see Thermal retention Rich earth 41ff, 51, 57, 63, 76 Rods 99, 120 Roof inclines 151 Roof insulation 75, 119 Room climate 164, 179, 208f, 214 Rotting 187 Round timber 82, 117, 188 R-values see Thermal resistance R Saddle-like application method 34, 102, 106, 122, 290 Salts 127 Sand 44, 171f, 174 Sawdust 53, 136, 203 Scratch pattern 124 Scrim tape 154, 166 Sealant 184 Sedimentation 50 Self-building 20, 26, 32, 40, 139, 188, 191, 197 Self-produced bricks and panels 136 Settlement 53f, 86, 96, 165 Shrinkage 42, 64, 66, 180 Shrinkage of soils, measuring 51 Shuttering see Formwork Silo 276 Silt 41 Slabs 151, 154 Slide rails 82, 87, 127, 166 Slurry see Clay slip Slurryability test 51, 57 Soaking 57, 127, 191 Soda 64 Soil 41, 43, 52 Soil formation 43 Soil identification 44f, 50, 198 Soil texture 41ff, 51 Solar radiation 206 Solid earth construction 11f, 16f, 33, 209 Soot soiling 127 Sorption 39, 162, 164, 210ff, 219, 232 Sound insulation 39, 75, 107, 119, 148, 155, 202, 227 Specific heat capacity c 203, 206 Specification 197 Spray application 131 Spray coat 169 Spray method 69, 78 Stabilisation with fibres 12, 42, 56, 174, 216 Stabilised earth materials 11 Stacked walls 148, 252, 258, 290 Stakes 99, 102, 107, 111, 117, 188 Sterile products 179 Stiffening horizontal battens 82, 86

Stone masonry with earth mortar 11 Straw 36, 53, 78, 174 Straw bale building 202 Straw content 76, 98, 174, 198, 203 Straw light earth 81, 96, 100, 106, 112, 175, 190, 202, 221 Straw light earth plaster 202 Straw, chopped 12, 33, 53, 66, 172, 174, 198, 203 Straw, chopping, shredding 66 Straw-clay 33, 44, 66, 69, 98f, 111, 116f, 124 Straw-clay plaster 174 Summer heat protection 119, 206 Supporting framework 82 Surface temperature 38, 129, 158, 199, 208f, 218 Surface weight 38, 227 Swelling behaviour 216 Tampers 96 Tempering 77, 98, 112, 221 Test consistency 45, 51 Test cubes 77, 197, 199 Thermal bridging 201 Thermal comfort 208 Thermal conductivity λλ 199 Thermal damping 199, 203, 208 Thermal dissipation 174, 208 Thermal effusivity e 208 Thermal insulation see Insulation Thermal insulation system 160, 206 Thermal lag 209 Thermal mass 119, 148, 206, 208 Thermal properties 199 Thermal resistance R 196, 201f, 209, 218 Thermal retention 39, 75, 107, 129, 199, 203, 206, 209 Thixotropy 64 Tiling 184 Timber frame construction 13, 33, 82, 187 Timber joist floors 226, 230 Topcoat plaster 169, 172, 176, 179 Topsoil see Soil Training course 20, 29 Transporting light earth 78 Triangular battens 142, 145 Trickle protection 109, 116, 154 Trowel 99, 171 Tumbler mixer 73, 190, 276, 278, 288 Twin posts 82f, 162, 242

Undercoat plaster 145, 165f, 172ff, 179f Urine 66, 177 U-value 39, 119, 196, 202 Vapour barrier 38, 131, 219 Vapour convection 219 Vapour diffusion 39, 210, 218 Vapour diffusion resistance factor μ 210 Ventilation 213, 218 Verification of applicability 195 Very lightweight mixtures 37, 75, 93, 119, 146, 198 Viscosity test 62 Volumetric heat capacity S 203, 206 Wall base 159 Wall chases see Installations Wall coverings 184 Wall elements 86 Wall linings see Internal wall linings Wall thickness 81, 221 Wall-mounted cupboards 186 Wallpapers 178 Water absorption 215 Water glass 64 Water vapour see Vapour Wattle 14, 99 Wattle and daub 14f, 33, 98, 127, 128 Weak wood 188 Weather protection 13, 160, 187 Weeds 53 Wet rooms 184 Wetting 124, 215 Willow cleaver 99, 166 Willow rods 99, 166 Window and door linings 95, 142 Windows 83, 182 Windproofing 148, 160, 232 Wood preservation 162f Woodchip 53, 66, 73, 203 Woodchip light earth 37, 54, 80f, 188, 272, 294

Appendix  307 

Picture credits 2, 3 © CRAterre-ENSAG 9 Johann Kräftner 10 © CRAterre-ENSAG 17, 18 Nachlass Bartning, in: J.Bredow, H.Lerch: Otto Bartning, Verlag Das Beispiel, Darmstadt 1983, S. 73 19 Egon Eiermann 1904–1970, Bauten und Projekte. Wulf Schiemer, (Hrsg.), Deutsche Verlagsanstalt, Stuttgart 1984, S. 74 20, 23–25 Claytec®, D-Viersen 26, 17 © CRAterre-ENSAG 28 Laurent Ménégoz 34, 35 [Fauth 1948] S. 69f. 38 Vasko Drogiski 42 [Piltingsrud 2008] S. 3 43 [Hamer 1975] Abb.2 72, 73, 82 Claytec®, D-Viersen 78 Jonas Lee 79, 83 Hugo Houben 88 Eva Rubin 91 Carl-Christian Rheinländer 96 Uelzener Maschinenfabrik, Sulzbach 97, 98 Anne-Louise Huber 100, 101 Jonas Lee 102 Hugo Houben 103, 113, 131–133 Claytec®, D-Viersen 128 Peter Esch 135 Anne-Louise Huber 136 Ecoterre scop, F-Sauve 138 Hugo Houben 142, 148 [Grebe 1943] S. 386 und 387 143 Claytec®, D-Viersen 150 [Reuter 1922] S. 28 154, 155, 191 Franck Lahure 167, 188, 189, 200 Claytec®, D-Viersen 202 Conluto®, D-Blomberg 206, 207 Franck Lahure 209 Andreas Dilthey 210 Teuvo Ranki 214 Claytec®, D-Viersen 215, 237 Conluto®, D-Blomberg 216, 253 WEM®, D-Koblenz 219–224 Carl-Christian Rheinländer 239, 240 Paproth/Claytec®, Viersen 244 Andreas Dilthey 251, 274, 288, 293-295 Claytec®, D-Viersen 276 Claytec®/Koculak 291 [Volhard 2010a] S.78 316, 317, 319 [Volhard 2010b] S. 28–30 321 [Lehmbau Regeln 2009] S.35 327–329 [Lehmbau Regeln 2009] S. 97–99 341 Gerd Anders 357 Olivier Scherrer 359 © CRAterre-ENSAG 384–387 Christian Delabie, ARBN, F-Caen

389, 393 Zeichnung nach Sonderveröffentlichung der Zeitschrift md, Konradin-Verlag Robert Kohlhammer, 1995. S. 116–120 390, 391 Lars Hallén, Nordiska museet 392, 394 Mikael Westermarck 395 [Lundsten 1992] S. 43 406–409 Eva Rubin 428, 430–432 Teuvo Ranki 434–439 Gaia Architects 450–454 Mikael Raymond 456–460, 462–469 Econest 472 St. Croix Ojibwe Tribal Housing 473, 477 Jonas Lee 474 Lou Host-Jablonski 479–481, 483 Alain Marcom 484 Pierre Henri Gomez 485 Juliette Bidart 486 Aymone Nicolas 488, 489 Sophie Popot 491, 492, 494, 496 Alexandre Douline 493, 495 Jean Paul Bellin 498-502 Schap_11 -Team 504, 505, 507-508 Vasko Drogiski 521–525 Florian Primbs, nzeb design ltd

When not otherwise stated, all other illustrations are by the author.

308 Light Earth Building

About the author

Franz Volhard (born in 1948 in Frankfurt/Main) is a partner of Schauer + Volhard architects (BDA) in Darmstadt. Since 1980, he has designed and built numerous light earth projects, many of which have won architecture ­prizes and awards. His extensive research has given rise to new techniques of using light earth for contemporary applications in sustainable building with wood and earth. He teaches and consults internationally and has lectured and published widely, including co-authoring the Lehmbau Regeln, the German earth building codes. He is member of CRAterre, the International Center for Earthen Architecture in France, and a founder member of the Dachverband Lehm, the German Association for Building with Earth.

Appendix  309 

Glossary

Additive A substance added in small quantities to improve the properties of a

material. Aggregate An organic or mineral material added during preparation of an earth

building material. Application class Classification of earth bricks according to their resistance to moisture

or frost. Board A flat, panel-shaped element with a thin cross section. Usually mounted

on a supporting structure. Clay The natural binding agent in soil and earth comprising particles that

are predominantly smaller than 2 microns. Earths with a cohesion (binding strength) greater than 3.6 N/cm² (see binding force test) are also termed clay. Cohesion Binding strength of an earth or soil. Compressed (earth) block An earth brick or block compressed in a mould. Consistency Denotes the plasticity of earth or the viscosity of a clay slip. Density of straw The mass of straw with respect to the volume of the resulting dry earth material in kg/m³. DIN Abbreviation of the German Institute for Standardisation Earth block Brick made of (heavy) earth, usually of a larger size. Earth brick Brick made of (heavy) earth, usually of a small size. Earth building material Building material made of earth, often with aggregates. Earth reel A wooden stake wrapped like a reel with straw-clay or light earth. Earth/soil A cohesive weathering product of stone comprised of clay, silt and sandy to stony particles. The term “soil” denotes the material as found in the ground. The term “earth” is used once the soil has been extracted or additionally processed for building purposes. Exposed timber frame Structural timber frame that is visible either on the inside or the outside of the wall construction. Fibre-clay An earth building material prepared with short organic fibres, typically with a bulk density > 1,200 kg/m³. Floor Construction element that separates the floors of a building. Half-timbered structure Traditional (vernacular) timber construction comprising a comparatively closely-spaced timber framework with infill panels, either left exposed or rendered. Heavy earth mixture Earth building materials with a bulk density > 1,200 kg/m³. Hemp light earth Light earth prepared with hemp hurds as the primary aggregate. Humus The organic component of soil (also topsoil). This is not suitable for building purposes. Infill, fill material A mass or material inserted into a cavity, e.g. between wall formwork, floor joists or rafters. Joist Horizontal beam in a floor construction. Lath Slender batten with dimensions typically