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P A U L I NA
WO JC IEC HO WSK A
THE REAL GOODS SOLAR LIVING BOOKS This Organic Life: Confessions of a Suburban Homesteader by Joan Gussow The Beauty of Straw Bale Homes by Athena and Bill Steen Serious Straw Bale: A Home Construction Guide for All Climates by Paul Lacinski and Michel Bergeron The Natural House: A Complete Guide to Healthy, Energy-Efficient, Environmental Homes by Daniel D. Chiras The New Independent Home: People and Houses that Harvest the Sun, Wind, and Water by Michael Potts Wind Energy Basics an d Wind Power for Home Home & Business by Paul Gipe The Earth-Sheltered House: An Architect's Sketchbook by Malcolm Wells Mortgage-Free! Radical Strategies for Home Ownership by Rob Roy A Place in the Sun: The Evolution of the Real Goods Solar Living Center by John Schaeffer and the Collaborative Design/Construction Team The Passive Solar House: Using Solar Design to Heat and Cool Your Home by James Kachadorian Independent Builder: Designing & Building a House Your Own Way by Sam Clark The Rammed Earth House by David Easton The Straw Bale House by Athena Swentzell Steen, Bill Steen, and David Bainbridge with David Eisenberg Real Goods Solar Living Sourcebook: The Complete Guide to Renewable Energy Technologies and Sustainable Living,
10th Edition, edited by Doug Pratt and John Schaeffer R E A L G O O D S T R A D I N G C O M P A N Y Y in Ukiah, California, was founded in 1978 1 978 to make available new tools to help people live selfsufficiently and sustainably. Through seasonal catalogs, a periodical ( The Real Goods News), a bi-annual Solar Living Sourcebook, as well as retail outlets and a Web site (www.realgoods.com), Real Goods provides a broad range of tools for independent living. "Knowledge is our most important product" is the Real Goods motto. To further its mission, Real Goods has joined with Chelsea Green Publishing Company to co-create and co-publish the Real Goods Solar Living Book series. The titles in this series are written by p ion eer ing indi vidu als who have fir stha nd expe rien ce in usin g in novat ive tec hnol ogy t o live lightl y on the plan et. Chels ea Gree n book s are bot h p rac tica l a nd ins pir atio nal, and they enlar ge our view of wha t i s p ossi ble as we ente r t he new mil len niu m. Stephen Morris
John Schaeffer
President, Chelsea Green
President, Real Goods
BUILDING WITH EARTH A Guide to Flexible-Form Earthbag Construction
Copyright 2001 Paulina Wojciechowska.
Unless otherwise noted, illustrations and photographs copyright 2001 Paulina Woj cie cho ws ka.
Title page photograph is used courtesy of Hartworks, Inc.
I de dicate this book to all my teachers in the world of Extract on page xi is from Eco Design Journal, vol. 3, no. 3, 1995.
natural building, and I thank each one of you for all the tremendous knowledge and help: Trevor Garnham of Kingston
All rig hts res erv ed. No par t of this bo ok may be tra nsm itt ed in any for m by any means without permission in writing from the publisher.
University, w ho taught me through out most of my architectural education and whose idea it was to write this book; Nader Khalili
Printed in the United States. First printing, June 2001
04 03 02 01
and Illona Outram of Cal-Earth, the pioneers of earthbag Superadobe construction; Athena and Bill Steeen of the
12 34 5
Canelo Project; Tom Watson, the silent inventor of, Printed on acid-free, recycled paper.
among many things, Pumice-crete; and all the others whom I met on the way who taught me
Due to the variability of local conditions, materials, skills, site, and so forth, Chelsea Green Publishing Company and the author assume no responsibility for personal
and took great care of me.
injury, property damage, or loss from actions inspired by information in this book. Alw ays con sul t the man ufa ctu rer , app lic abl e bui ldi ng cod es, an d t he Nat ion al Ele ctr ic Code. When in doubt, ask for advice. Recommendations in this book are no substitute for the directives of professional contractors , equipmen t manufacturers , or federal, state, and local regulatory officials.
Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book and Chelsea Green was aware of a trademark claim, the designations have been printed in initial capital letters.
Library of Congress Cataloging-in-Publication Data Wo jci ec how sk a, Pa uli na, 1967 Building with earth: a guide to flexible-form earthbag construction/ Paulina Wojciechowska. p.
cm. — (A Real Goods solar living book)
Includes bibliographical references and index. ISBN 1-890132-81-0 (alk. paper) 1. Earth construction. I. Title. II. Series.
TH1421 W597 2001 693'.91—dc2i
2001028676
CHELSEA
GREEN
PUBLISHING
COMPANY
Post Office Box 428 White River Junction, VT 05001 (800) 639-4099
www.chelseagreen.com
CON TEN TS
Acknowledgmen ts ix Introduction
3. G E T T I N G S T A R T E D :
xiii
1. EARTH ARCH ITECT URE
S I T I NG ,
3
Clay-Based Building Materials 5
AND
Design Considerations 29 Locating the Building on the Land 29
Adobe 6
Landscaping 30
Cob 8
Topography 30
Rammed Earth 9
Orientation 31
Wattle and Daub 10
Utilities 32
Straw-Clay 10
Building Shape 32
Papercrete 11
Planning Ahead 33
Earthbags 12
Site Preparation: Setting Out 33
When Are Earthbags Appropriate? 16
Foundations 34
Extending or Recycling the Building 17 Earthbags Forever 19
Earth-Filled Tires 39 Rubble or Mortared Stone 39 Gabions 40 Dry-stone 40
2. USING BASIC STRUCTURES FROM NATURE TO BUILD WITH EARTH 21
Arches 22
4 . B U I L D I N G W I T H
DESIGN,
FOUNDATION S
29
EART HBA GS
43
Materials 44
6 . W E A T H E R P R O O F I N G
FINISHES
AND
75
Tools 46
Earthen Plasters 76
Preparing the Fill 49
Application 77
Filling Bags or Tubes 50
Stabilization and Alternatives 78 Vegetable Stabilizers 81 Animal Products as Stabilizers 82 Mineral Stabilizers: Lime 82 Lime Plasters 83 Making Lime Putty (Slaking) 84 Making Lime Plaster or Render 86 Application 87
Filling a Bag with More than Three People 51 Filling Bags or Tubes with Only One to Three People 52 Using Small Bags 52 Tamping 52 Keying 54 Structural Reinforcement and Buttressing 54 Openings 57 Arched Openings 58 Square Openings 60 Bond Beams 60
Pozzolanic Additives to Lime Plaster 87 Stabilization for Waterproofing 88 Stabilization with Cement 89 Application of Stabilized Renders 91 Interior Finishes 92 Sealants 92
Pumice-crete 40 5. R O O F S
65
Brick or Adobe Roofs 66 Vaulted Roofs 67
Making the Arch 24
Conventional Roofs 68
Vaults 24
Water-Catchment Roofs 68
Apses 26
Thatched Roofs 68
Domes 26
Living Roofs 70
Corbeling 26
Low-cost Flat Roofs 71 Roof Insulation 72
Paints 94 Clay Slip or Alis 95 To Cook Wheat Flour Paste 96 To Make Alis Clay Paint 96 Application 97 Lime Paint or Whitewash 97 Additives to Lime Wash 97 Recipes for Water-Resistant Whitewash 97 Some Old Limewash Recipes 98
viii
ACKNOWLED GMENTS
Casein 98 Recipe for Interior-Exterior Casein 99 Application 100 Oil-Based Paints 100 Maintenance 100
8.
THE
EART HBA G
A D V E N T U R E
123
Shirley Tassencourt's Domes, Arizona 123 Allegra Ahlquist's Hou se, Arizona 127 House Built by Dominic Howes,
7.
OT HE R
INTERIOR
FLOORS , BUILD ING
AN D
WAL LS,
FURNISHINGS :
WI TH
CLAY
1 03
Finding and Analyzing Building
Wisconsin 128 Sue Vaughan's House, Color ado 130 Carol Escott and Steve Kemble's House, the Bahamas 131
Soils 103 Jar Test 104
Kelly and Rosana Hart's House,
Testing by Hand 105
Kaki Hunter's and Doni Kiffmeyer's
The Right Mix 105 Thin Partitions and Ceiling Panels 109 Insulation 110
Colorado 135 Honey House, Utah 140 The Lodge "Njaya," Malawi 142 The New House of the Yaquis, Mexico 143 Afterword 148
Interior Detailing 114
Bibliography 149
Earthen Floors 115
Resources 153
Construction 118 Sealants, Maintenance, and Repair 119 Electricity and Plumbing 120
and Athena Steen, and Tom Watson for their generosity in everything they gave throughout the many months of my travels, which enabled me to write this book. I would like to express my gratitude to all those who helped me put this boo k t oget her in man y dif feren t way s, som e of wh om I me nti on below : From Kingston University, I would like to thank the Green Audit Research Project for partly funding and enabling me to commence the writing of this book. Thanks to Peter Jacob, Bryan Gauld, and Sue Ann Lee. Also to Trevor Garnham for guiding me through the process. From the Green Audit room at Kingston University: Cigdem Civi, Helen Iball, and David Lawrence. Friends in England whose help was invaluable: Flora Gathorne Hardy for her help, photographs, and immense support and belief in this book; also to Salim Khan, Bruce Ure, and Shahnawaz Khan for their technical support; and to Tim Crosskey, Henry Amos, Wasim Madbolly, and Max Jensen for the photographs; and to Adrian Bunting for the Malawi project. Friends who contributed their stories and photographs in the United
Straw-Light Clay 111 Hybrid Earthbag and Straw Bale 113
I would like to give special thanks to Nader Khalili and Iliona Outram, Bill
Index 158
States: in Arizona, Bill and Athena Steen, also Allegra Ahlquist, Shirley Tassencourt, and Dominic Howes, who shared information as well as huge amounts of love and support throughout the whole process, together with Carol Escott and Steve Kemble, and a very big thank you for being there in those very difficult times. In California: Michael Huskey. In Colorado: Kelly and Rosana Hart. In Utah: Kaki Hunter and Doni Kiffmeyer. In New Mexico: Joseph Kennedy. Also I would like to thank Ian Robertson in California for his support, Gene Leon for early editing, Frank Haendle in Germany for communica-
X
tions, Lydia Gould for all the survival help in Mexico, and Athena and Bill Steen for making that trip possible. It is impossible to name all the people to whom I am very grateful, who were so wonderful throughout my travels, but I would like to quickly mention some not yet named, who looked after me and helped me to make my journeys: Simon Clark, John Jopling, Vanita and Alistair Sterling, Heidi Koenig, Catherine Wanek and Pete Fust, Satomi and Tom Landers, Kat Morrow, Karen Chan, Carole Crews, Cedar Rose, Lynne Elizabeth, Cassandra Adams, Leonard Littlefinger, Lance Charles, Ralf and Rina Swentzell, Arin Reeves, George Mohyla, Doc Clyne, Giovani Panza, Craig Cranic, Michael Smith, Elizabeth Lassuy, Reto Messmer, Kevin Beale, Stokely Webster, Monika Falk, and Christina and Markus Lehman. Without my family, who provided me with constant help and support, the "journey" and the writing would have been more difficult. I would like to thank my parents, Mar cjanna Sojka and Krzysztof Wojciechowski, and my stepfather, Witold Sojka. My special thanks are extended to my partner, Christof Schwarz, who has endured many absences and who has provided constant support, encourage ment, and help with writing this book, for which I am immensely grateful. Finally, my thanks to the publishing team at Chelsea Green, especially Jim Schley, Hannah Silverstein, Ann Aspell, and Rachael Cohen, who have carefully edited the text, illustrations, and photographs. ... being surrounded by beauty allows one to put aside at least some of the burden of his or her defences against the world and to feel inwardly free. What relief! What therapy!
Unlike composition, harmony and so on, beauty rules. It is something the artist must struggle to achieve. And anyone who undertakes this struggle, with all the single-minded dedication it demands, is an artist. This love force shines from the finished prod uct. It has nothing to do with fashion or style, and little to do with latent ability. It comes from the gift of love, and an environment so filled has a powerful healing effect,for love is the greatest healer, needing only understanding to complete it. —Christopher Day, from "Human Structure and Geometry"
INTRODU CTION
had a wish—to be able to go to any
I
take a path other than the so-called mod
place on this Earth and bu ild a shelte r
ern way.
with the materials available to me
Most primitive buildings were con
from the surrounding environment. I had
structed by an anonymous builder in re
already learned about building with wood,
sponse to such conditions as climate, ori
stone, clay, straw, lime, and many combi
entation, and the availability of building
nations and permutations of all these. The
materials. Building materials dictated the
material that would fill in the gap, that
form of each structure. The builders were
would give me the complete confidence
sensitive to their materials; they worked
that I would be able to build a house al
with them, not against them as so much of
most anywhere, was sand.
today's architecture seems to do.
I spent most of the impressionable
A few years ago, I was working in an ar
years of my life in Afghanistan and India,
chitectural office. I was always at the draw
where I was surrounded by indigenous ar
ing board doing technical drawings, not
chitecture. It was during that time, I sus
really understanding the materials I was
pect, that I develope d a p assio n for hon
working with or why they were used. How
esty, modesty, and h armony in design. All
were critical decisions made? Did the best
the way through my architectural studies,
choices depend on cost, aesthetics, or sur
I was drawn to what I call "primitive" ar
roundings, or was the process driven by
chitecture. By "primitive" I don't mean
peopl e wh o we re ju st stuck in their ways,
backwar d, but quit e the oppos ite. To be
dictating by convention and code how
primus means to be the first, to be at the begin ning: primary. It is good for the min d
buil dings shou ld be designed? In time , I
to go back to the beginning, because the
learn by using my hands. It was necessary
California.
realized that to find another way I had to
begin ning o f any estab lished h uma n activ
for me to experience actual construction, a
ity is often its mom ent of greatest wonder.
time of very basic building. Always start
The original forms can teach us the fun
with the basics—the first principle of
damental principles of each invention,
natural building.
showing us the possibility that we might
Facing page: Earthen structures at Cal-Earth,
An opportunity came up to participate xiii
xiv
INTRODUCTION
in a workshop for people who wanted to
which is exactly what I needed after all
learn to build. It was to be three intense
those years at the drawing board. It was
weeks of building a house for the Othona
great! These experiences reinforced my
Interior of the author's Earthmother Dwelling retreat.
Here is an extract from my diary, describing my thoughts when I first arrived at Cal-Earth:
Community Retreat in Dorset, England.
need to go away to places where people
It's early morning as I step outside the house. Mist covers the
The course was run by Simon Clark of
were building using basic principles and
bott om o f the m ount ains , sil houettes of shabby Jos hua trees , a
Constructive Individuals, an organization
materials, places that would give me more
tree that stands so still all the time. The sand is lit up, the
in London that offers training to people
opportunity to discover indigenous build
mountain towers above the mist. The cold is sharp, the sun is
who wish to build their own homes or ex
ing materials and techniques, freed from
bright . In the f oregro und I see domes and des ert ar chitectu re,
tend or alter an existing dwelling, or who
the rigid commercialism of London archi
like sand dunes. The landscape looks and feels right. Instead of
simply want to have the building process
tecture.
destroying the view of the mountain beyond and Joshua trees around and the vast openness, the structures enhance the view.
demystified. How wonderful this oppor
In the autumn of 1 9 9 6 , I finally em
tunity sounded, to build a whole house in
bark ed on my long-a waited journ ey. My
just three weeks! I ju mpe d at t he ch ance.
first three-month stop was at the Califor
am happy they exist and have become an integral part of this
nia Institute of Earth Art and Architecture
landscape. I walk toward them, at first looking around the
niques and also raised man y ecological is
(Cal-Earth). Set up by Iranian-born archi
outside. I realize that they are sunken into the ground. They
sues. This particular hom e was designed to
tect and autho r Nader Khalili and his Brit
feel very solid and permanent. Yes, they have this permanence
have minimal impact on the environment
ish associate Iliona Outram, this school
and belonging about them, a permanence that a timber house
by usi ng r ecycled- newspa per i nsul ation , a
takes people on apprenticeship retreats for
does not have. Once I walk inside, they feel cool. They have
composting toilet system, solar electric
a week or more. During this time, Cal-
soaked up the night's cold air. I am drawn toward the one that
modules, a graywater system, and a leach-
Earth and its associates contributed to
looks like an animal. It has a fireplace and a small niche to hide
field to nour ish fruit trees. There it all was,
teaching me of the "magic" simplicity of
in. Ideas flow into my mind of a house I would like to build
and it had a nam e: Ecological, Sustainable,
earth architecture. Working with the earth
right now for myself, with a network of rooms all interconnect
and Environmental. These were the words
empowered me to carry on, as it has em
ing, partly undergrou nd. The outside is very intriguing as well.
used for the simpler ways of building I had
powere d many o ther i ndivi duals . I lea rned
I imagine patterns forming from the way the plaster has been
dreamed of. I knew that after this work
the basics of earthbag construction (called
applied and outlined. After a while, I proceed to the other
shop I would know what to ask for. A whole
Superadobe at Cal-Earth) and spent time
attractive-looking earth shelter. This one is totally covered in
new world was opened to me.
researching this method, trying to push its
earth, or so it appears. It has tiny circular windows going all
limitations and explore its possibilities.
around at the lower level, great for children if they want to look
The course covered construction tech
After the Dorset cours e, I became mu ch
XV
I do not feel disturbed by their presence. Quite the opposite; I
more confident in handling tools, and
To simplify is the aim. What a joy to
out. The light at sunrise is amazing; it floods in though one
many of the mysteries behind building a
learn and to fulfill my dreams! I spent a
larger window. Because of the partially white wall, the room looks bright. The primitive paintings on the wall stand out.
house were gone. I had finally experienced
wonderful three months, studying as well
what it felt like to build. I got to "feel" the
as building my own retreat. For the first
The light covers the horizon; the sun is a little higher, but the air is still sharp. I sit in the sun's rays to warm myself.
materials, feel what concrete is like, feel
time in my life I could design and build a
what working with wood is like, and learn
house with no restrictions from anyone. I
how all the pieces go together. I also expe
was free and I felt free and therefore I ex
light beautifully percolates throug h the bricks. The top of the
rienced the harsh realities of building,
press ed freedom .
dome is open. This one feels the coldest so far, probably
After some time I get up and walk into a brick dome. The
The author's earthbag retreat before plastering.
The author's retreat during plastering.
xvi
xvii
INTRODUCTION
because none of the openings are
traditionally, for example in Islamic archi
poin ts for obser ving who was appr oach
like sculpting. When sculptors carve rock,
glazed, and I feel the air moving
tecture. Rather, this passion has to do with
ing. The seating areas were to be niches so
they listen to the rock telling them what it
through. I walk to the center. The
the prevalence of arched forms in nature. I
three or four people could sit facing each
needs to become. Designing and building
acoustics are amazing. The sounds that
did not necessarily want to imitate nature.
other. And a child who lay sleeping in a
a dwelling is likewise about under standing
I make with my feet bounce around
I wanted to experience the freedom that
niche would be able to see the fire burni ng
the material, the needs and passions of the
and seem very loud. What a great place
nature appears to possess. I had experi
opposite, for comfort. I wanted the ceiling
inhabitants, and the climate and other
to play music this would be. After a
enced so many constraints in the world I
to be high, since we often judge a space by
characteristics of the site. The challenge is
short pause, I proceed to the Three
came from that I wanted to escape rules
its volume. Although the main room was
to be in harmony with your environment,
Vault House. Whoa! Rectangular
and regularity. I wanted to become free.
rooms, white walls—it feels like a
So my ideas just came as I went along.
only 10 feet (3 meters) in diameter, ten
and most of all to feel passion during the
people could sit comfort ably inside with
process .
out feeling claustrophobic.
chapel. A lot of different-sized open
Later, looking back, I could translate these
ings and niches in the walls. A cooling
ideas into theories about design and con
An earthbag dome sunken into the
tower under constructi on. A very large
struction, but that is not how it started.
ground creates and encloses a space. Bas
From the moment I started to build, I
space in comparison to the others. T he
The accompanying drawings and photos
ing your design upon that central enclo
recognized that it was essential to main
light reflects off the walls in a soothing
give a sense of how I went about designing
sure, you can add or take away as you
tain trust in the material. Without this to
way. It feels airy and open. There are
and building the retreat.
please and as the s tru ctur e allows. Build ing
tal trust, you fall back upon narrow ideas.
To begin with, I spent many days look
with earthbags is not like digging a cave,
To push any process forward, you need
ing around the site thinking about where
scraping away at the earth to hollow out
trust. Unless you build with feeling, you
to place my tiny retreat. I found a lovely
the shape of the building, an d it's not like a
will not feel true contentment with the fin
My desire to build using the earth, uti
spot, away from other structures. A lonely
wooden or concrete house where every
ished product. When you merge the natu
lizing the earthbag technique, was very
Joshua tree stood in a clearing of sorts. I
thing has to be precisely placed to accom
ral and the human-made environment
strong. There were many reasons for this,
wanted to be close to the tree, having it in
modate manufactured materials. Building
into one, when you listen to the sun and
including a longing to research an un
front of my courtyard, with the entrance
with earth, you can add as well as remove
the wind and the natural forces all around,
known material, to understand and cel
facing east, because the strong winds came
material to create the shapes you desire.
ebrate its possibilities. I also wanted to find
from the west. I wanted the retreat to pro
out what it takes for a woman with few
vide a place to sit facing the courtyard and
freedom. I wanted to celebrate this. As I
manual skills and little strength to build
the Joshua tree.
worked with this totally fluid material,
more buildings here than I expected— but wh at did I expect?
The earthbag allowed me a great deal of
single-handedly a shelter for herself and
When planning the retreat, I tried to
earth or sand in bags, I wanted the materi
her children. I wanted to indulge in the
figure out what I would like inside it, never
als to lead me. I did not want to make it
freedom of using earthen materials, hav
restricting my imagination. I knew that
imitate another kind of building. I wanted
ing learned about the structural form of
peopl e who stayed he re woul d need a place
to set the dome free, to listen to it. I was
the arch, which allows the use of only
for their luggage, a place to sleep, and per
build ing with love, creatin g some thin g
earthbags for the whole structure, with no
haps a place for a child to sleep. So I de
that felt right. I believe that all buildings
reliance upon wood.
signed for a couple and their child. A fire
should be designed and built with sensi
place w ould be used to ke ep w arm and to
tivity. To me, love has become the most
form has little to do with the ways sym
cook on. Then I thought of the views, the
important factor in designing. In fact, I
metrical domes or vaults have been used
light, sunrise and sunset, and the lookout
now see that designing and building are
My passion for the arch as a structural
To me this is what contributed to my retreat's soul.
East
xviii
The author (in
BUILD ING
foreground) with lliona Outram (behind) and other Cal-Earth visitors inside the Earthmother Dwelling.
the building can be an organic extension
basic i ntr odu ctio n to some o ther forms of
of the land and the outcome of a marriage
"alternative architecture." You have to un
between w ind, sun, a nd th e soul of the on e
derstand that this is a drop in the ocean. I
who dwells there.
can only introduce the concepts, sharing
At the moment, my ideal house is one
some of the lessons I have learned and
that lives in such harmony with its envi
sights that I have seen. Numerous books
ronment. It is a house that is difficult to
have been written on many of the natural
notice, like an animal that blends into its
construction techniques, some of which
surroundings. So many houses appear like
can be ordered from the organizations
warts in our landscape. When you drive
and bookstores listed in the resource sec
through the countryside, how much nicer
tion. However, to my knowledge, no one
it would be if you couldn't see the houses,
has written a book-length work about the
if they blended in harmoniously, like the
earthbag
houses that climb the hillsides in Afghani
short articles for various magazines. This
construction
technique,
only
stan, made of the same earth as those hill
was my primary reason for putting pen to
sides. Only at night, when the lights come
pape r—t o pr ovide some of the t heoret ical
on, do you see the extent of the develop
knowledge that I gathered in the places to
ments.
which my research took me. That theoreti
In building my "Earthmother Dwelling
cal foundation is necessary to begin con
Retreat" at Cal-Earth, these are some of the
struction, but the reader must remember
sensitivities that I brought to the process.
that no amount of theory can teach as
In this book, I will give a thorough in
much as your own hands. Happy experi
troduction to earthbag construction and a
menting!
WI TH
EA RT H
1
EARTH
ARCHI TECTU RE
S
ince the earliest times, people have lived in the e arth, taking up residence in existing structures or forming and sculpting earth around them according to their needs. In terms of
growth and development, indigenous communities usually lived
within the limits of their ecosystems. Nature, technology, and cul ture maintained a balance. Until the industrial revolution, most of the world's people housed themselves in earthen architecture (Khalili 1986,58). Even today, it is estimated that a third of the human population lives in houses constructed of unbaked earth. But, during the industrial age, the use of engines and fossil fuels expanded the limits of local ecosystems. Resources from distant regions were brought toget her in the process of mass production. Industry on an unimaginable scale transformed the landscape, while the goods manufactured on assembly lines transfor med our values. Yet for a long time the environmental consequences of mod ern design seemed remote. At the beginning of the twentieth century, architects were inspired by machinery, not by nature. Modernist s saw buildings as isolated ob jects, n ot as p art o f larger systems o r com muni ties . The d esigns o f the industrialized world have developed to depend on materials
Above: An afternoon snooze in the city of Petra, Jordan .
and technologies beyond the limits of what local ecosystems pro vide. It may seem as if technology has given people the freedom to override the laws of nature. But if we use that freedom, we must take responsibility for making these choices. Today, our global technologies are depleting the Earth's resources, darkening the water and skies with waste, and endangering the diversity of life. Can we find a way of life that will re-create a balance between na
Facing page: The ancient city of Petra, Jordan, carved
ture, humanity, and technology?
out of sandstone.
3
EARTH ARCHITECTURE
4
5
Today, timber, steel, and cement are not
ing houses, the use of local materials is
niques with elements of modern technol
manner: She inspires and advises her pot
readily available in many parts of the
beco ming increas ingly imp ort ant , amon g
ogy, permit people to build dwellings that
ters what to do while working with clay.
world. They must be transported from
many other environmental aspects. Using
are appropriate for the sites and climates
There is a Tewa prayer, of which the
thousands of miles away. For the people
local materials not only saves energy and
where they are built. It is beyond the scope
Santa Clara Pueblo poet and potter Nora
who live in those regions, it would make
resources, it gives builders and dwellers a
of this book to provide detailed descrip
Naran jo-M orse says (Swan & Swan 1 9 9 6 ) ,
more sense to build their own houses out
sense that they are grounded, a sense of
tions of each natural building technique,
"This prayer continually renews our rela
of what is "beneath their feet" and to use
belon ging, which is missi ng when "for
and the books listed in the bibliography
tionship to the earth, her gifts, and [the
the materials withi n their reach. Yet in the
eign" materials are used. In the southwest
provid e m ore compre hensi ve infor mation
less industrialized countries, where mod
ern United States, for example, the Pueblo
on adobe, cob, rammed earth, straw bale,
ern building materials are used by the privi
peopl e have tradi tiona lly used adobe , a
and other methods. Here I will give brief
leged few, poor people often look down
sun-dri ed clay brick, because sun and clay
introductions to several traditional tech
upon the ancient construction methods
are easily acquired and worked with. In the
niques that are especially useful in combi
and scorn the earth as a building material.
northeastern United States, houses were
nation with earthbag construction.
In response to this, some designers and
traditionally made of wood, not because
build ers, inclu ding the late Egyptia n ar
clay wasn't there, but because wood was
chitect Hassan Fathy, have attempted to
plentiful and easily avail able. In Englan d,
BUILDI NG
peo ple] ." Clay Mother, I have come to the cen ter of y our adobe, feed and clothe me and in the end you will absorb me
CLAY-BASED MATE RIAL S
into your center.
However far you travel,
revive ancient techniques, building earth
parti cular ly in Devon, cob was the p opul ar
A critical ingredient in durable, resilient
houses for the poor as well as for the rich.
buil ding mater ial, as the soil was perfect
earth for building is clay. In response to
Earth has been used to build on moun
for forming the loaf-shaped lumps that
cultural, climatic, and geographical differ
Clay is the result of the chemical weath
tains, cliffs, marshlands, and the harshest
constitute the basic building block in this
ences throughout the world, many varia
ering of rock and silicates such as feldspar,
do not go crying.
of deserts. With a suitable mix of ingredi
method. Sadly, people have almost stopped
tions of clay-based earth architecture have
quartz, and mica. The diameter of clay
ents and appropriate design, earth can be
buil ding earth house s in Engla nd, now
been develope d. These techn iques can be
grains is smaller than two one-thou
used to build almost anywhere in the
that bricks and concrete are cheap and
traced back thousands of years; for ex
sandths of a millimeter. There are several
world. Why not continue to use earth and
available.
ample, traces of mud walls from more
types of clay, but the most commonly
other natural materials where it is appro priat e to do so?
In the United States today, builders are
than two thou sand years ago were found at
found are kaolin and montmorillonite.
gradually returning to older and more
the Tel Dor excavations in Israel (Stern
With an electron microscope, one can see
One of the reasons for the revival of
natural construction techniques. People
1994) 133). Parts of the Great Wall of China
that these materials are wafer-thin, foli
earth architecture and for the sudden rise
are learning from ancient European earth-
are built out of earth and are still standing
ated, and scaly crystals.
of interest in alternative ways of building is
buil ding t radi tion s s uch as cob a nd watt le
today. In many cultures , clay has long been
Earth alone (without the use of forms)
the change in people's level of conscious
and daub, as well as from the traditions of
considered a magical material. It is written
can be used for construction only if it con
ness. A growing movement to promote
the Pueblo Indians adapted from the
in holy books and poems that humans
tains some kind of stabilizing element,
"natural," "environmental," "sustainable"
straw-clay adobe building technique that
themselves were created from clay.
which in industrialized architecture is of
understanding is now trying to make
was brought by the Spanish a few centuries
In the Pueblo cultures of the American
ten cement. In traditional natural build
peopl e aware of the devast ation that we
ago. New methods, such as straw bale and
Southwest, one of the deities is the Pueblo
ing, we use clay as the binding material,
have caused on our planet. Among those
earthbag construction, which combine the
Clay Lady, who is said to live in each piece
due to the cohesive properties of the clay
designers and builders involved in build
benefits of a variet y of trad iti onal tech-
of clay pottery made in the traditional
molecules. These molecules are attracted
6
EARTH ARCHITECTURE
7
to each other, therefore producing a stron g
popu lar as a base for inter ior and exterior
it is very inexpensive to build with ad obe if
bon d. If clay parti cles are well dist ribut ed
plasters and cons truc tion materi als. This
you do the work yourself.
throughout the soil, they form a coating
is largely due to cost and energy savings,
The Taos Indians of New Mexico have a
around the particles of silt, sand, straw,
and to the way that houses buil t with clay-
long tradition of earth building using
and gravel or other filler used, effectively
based materi als are mor e aesthetica lly
adobe. Adobe houses are part of the cul
pleasin g and h ealthi er to live in, especially
ture of the Pueblo people. They go to
bind ing them together . On drying, the swollen clay shrinks un
for chemically sensitive individuals.
gether like Eskimos and igloos. Du ring the
evenly and causes shrinkage cracks. The
See chapter 7 for more detailed infor
perse cution s by the Spanis h and by the
more water that is absorbed by the clay, the
mation abo ut working with clay as a build
Americans the adobe walls protected the
larger the cracks will be after drying. Each
ing material.
Pueblo people and allowed them to keep
type of clay has a different chemical com posi tions , b ut above all t hey va ry i n t heir
many of their spiritual beliefs, attitudes, A D O B E
and practices to themselves.
water-absorbing qualities. Kaolin absorbs
Adobe blocks are sun-dried mud bricks
The beauty of earth architecture is that
water the least, while montmorill onite can
that can be stuck together with mud mor
it participates in the natural environment.
absorb seven times as mu ch water, and can
tar to create thick walls. They have been
It is part of a continuou s cycle, unlike con
swell to sixteen times its volume. Working
used for thousands of years in North Af
temporary
the clay with your hands enables the clay
rica, South America, Asia, and the Middle
where structures are built to stand inde
particl es to pack tog ether in den ser, p aral
East, and were brought i nto the southwest
pend ent of and unaffected by their sur
lel layers, creating st ronger bindi ng force.
ern United States by the Spanish. The
roundings. Build, live and die, build, live.. .
As a result, the tensile and compressive
Spanish learned about adobe construction
Adobe houses, like other earth houses,
strength is greater, up to 2 0 percent more
from the Egyptians, who still use this an
have to be cared for continuously and
or adobe houses to live on we have to take care of them, like
than in mechanically compressed blocks.
cient building technique. Using the arch,
when their useful life is over, they are given
you would take care of a child. You coat the child, we plaster
Many different types of traditional earth
dome, and vault, it became possible to cre
the respect of being allowed to melt back
construction require some clay as the
ate houses using only earth (Fathy 1 9 8 6 ) .
into the earth. For example, a house is
binde r for coh esion, inclu ding a dobe, cob,
Many magnificent large adobe structures
boar ded up after the death of its owner.
it lives with you. Wh en you keep the house warm it will keep you
rammed earth, wattle and daub, and
are still in use in Africa, Asia, and the
New people m ovin g in will mo ld new ado
warm. If you die the house will also die with you. When you build a
blends of clay with straw or other fibers.
Middle East.
bes from the mater ial rema ining , and the
Because of serious, building-related envi ronmental
problems
in
industrialized
While in most of the world's countries adobe is used for the poor, in the south
industrialized
architecture,
cycle will cont inue. Adobe structures flow out of the earth,
Adobe houses in Taos Pueblo, New Mexico.
the adobe houses, so they can stand up. Whe n you live in a house the house is almost like a part of you because you live in it and
house, you build the house with what you're actually standing on. Once upon a time there might have been a house there also, but the recycling of the adobe material is almost like building what had been there once upon a time.
countries, in recent years we have seen a
western United States it is increasingly
and it is often difficult to see where the
dramatic revival of traditional building
fashionable with the very rich to live in a
ground stops and the buildings begin. By
—Jo e Martinez, Taos Pueblo,
techniques based on clay. Clay is non
healthy, natural house. Because adobe is
using adobe to build the walls of a house
quoted in At Home with Mother Earth
toxic, recyclable, and easily available in
very labor intensive, it is very expensive to
and cob to sculpt the interior, beautiful,
many parts of the world. Combined with
pay some one else to buil d and finish an
curved forms can be fairly quickly con
sand, gravel, and natural fibers such as
adobe house. But, because the materials—
structed that provide very inviting living
straw and wood, clay is again becoming
the earth at your feet—are practically free,
space while also providing the mass
(Feat of Clay, 1995)
8
EARTH ARCHITECTURE
needed for a building to perform well thermally. Ovens and seat
earth structure can be made if a minimum
ing as well as walls can be created using adobe finished with an
of 5 percent clay is present to bind the soil
earthen plaster. (See chapter 7 for more discussion of how to use
and if wood or other material is available
adobe in conjunction with other earthen techniques.)
to make temporary forms.
The traditional method of adobe preparation is a highly labori
Adobe house of Hassan Fathy, Egypt.
Rammed
earth
is
another
ancient
ous process. The strength and durability of the finished dwelling
earth-building technique currently being
depends up on the quality of the bricks. Adobe bricks are produced
revived in many parts of the world. The
by putt ing the a ppro pria te soil, clay, and stra w mixtu re int o a mold
Great Wall of China is partially built out of
where the mix is worked lightly by hand then quickly removed. The
rammed earth, and this technique has
mold must be clean and wet to ease removal of the formed brick.
been us ed in Yemen to b uild stru ctur es as
Adobes can also be made without forms, but a large quantity of
high as seven stories. In eighteenth-
mortar must be used to smooth out the unevenness of the joints.
century France, a pioneering architect named Francois Coin teraux tried to revive
Adobe is someti mes criticized for being a very soft material, bu t adobe construc tion is a system. That is, no single brick is subjected
graded subsoil mixed with plenty of straw
rammed earth construction with little
to intensive pressure, because the overall wall, which is stronger
requires no other additives to make good
success due to fear of competition among
than its individual par ts, carries the weight of the roof. To add to its
cob for building.
other builders. Currently in France, the
strength, a dobe can be reinforced with a diversity of fibers.
A boy making adobes in Peru.
9
The durability of a cob house depends
use of earth as a building material is being
on how much energy is pu t into it as well as
revived by the organization CRATerre. In
CO B
what is in the mix. If a cob walls fails it is
Cob is like an adobe mix with as much straw as the mud mixture
usually not the fault of the material but of
can accept before it fails to bind. That is, subsoil containing clay is
the builder. Like adobe houses, if the cob
mixed with straw and water and brought to a suitable consistency
house is loved and cared for it will last for
by kne ading or t readi ng. The l umps of eart h (or "cobs ") are th en
a long time.
placed i n ho rizo ntal layers to form a mass wall. Th e bul k of a cob structure does not always consist solely of cob mixture. Cob that
RAMM ED
contains gravel or rubble can be sculpted into walls, making the
This is another age-old technique that uti
whole structure more resistant to moisture, allowing more air to
lizes only the eart h to create thick, durable
circulate inside, and keeping it drier.
walls, which can be load -bearing, low-cost,
EARTH
Cob was traditionally a popular building material in the west
heat-storing, and recyclable. Rammed earth
ern parts of Britain, mostly Devon and the southwestern regions,
structures can be built in a variety of cli
because the soils of tha t r egion are amon g th e bes t i n Br itain for
mates and will last for hundreds of years.
earth construction. Most soils there contain a good proportion of
The construction procedure is simple. A
clays that are fairly coarse and therefore do not expand and con
mixture of earth is rammed between
tract extensively and which provide adequate cohesion. Secondly,
wooden forms. The forms are removed,
these soils are usually found to contain a well-distributed range of
creating thick walls that need no external
aggregates, from coarse gravel to fine sands and silts. A good, well-
finishes. The most basic type of rammed
Rammed earth house in Arizona.
Cob fireplace sculpted by Kiko Denzer at the Black Range Lodge, Kingston, New Mexico.
EARTH ARCHITECTURE
Australia, it is a popular alternative build
11
earthbag wall. Other combinations of fi
Advantages of Adding Fiber
ing technique, and its modern application
ber, clay, a nd s and ar e pr obably being de
in the United States has been pioneered by
Some of the many advantages of adding
veloped, as the possibilities are endless. See
David Easton, who updated Cointeraux's
fibers such as straw to an earthen mix are:
chapter 7 for more detailed discussion of
techniques with improved engineering, sophisticated forms, and innovative design to make rammed earth cost-competitive with conventional construction. Modern
A wattle panel under construction.
equipment speeds the process. The soil is
controlling the shrinkage cracks
•
increasing tensile strength
Earthen materials and natural fibers
•
improvin g insulation value
work together extremely well, preserving and protecting one another, and combin
There are also many advantages of coating natural fibers with earth:
mixed on-site and then poured into the
straw-clay mixtures.
•
ing the earth's thermal mass with the fiber's insulative value. Bill and Athena
wooden forms set up on top of an appro
clay and straw. When dry, the surface can
•
increasing compre ssive strength
Steen, who have been using straw-clay
priate foun dati on (usually stone or con
be pl astered with a mi xtur e of l ime, sand,
•
providing fire resistance
techniques in Mexico, have said "they can
crete). An earth mixture with a moisture
and animal hair and painted with white
•
improvi ng wate r resistance
content of 10 percent is then rammed in 6-
wash. Chapter 6 describes lime plasters
•
improving insect resistance
to 8-inch layers using pneumatic or hand
and finishes for use on any earthen wall.
the local climate. Like the rest of life, build
STRAW-CL AY
founded on a good relationship. For us,
tampers. The forms are removed, reveal ing a 2 -foot-thick wall that is then com
be bui lt fr om pr edom inan tly local mater i als in whatever combination best matches ing can be much more fulfilling when
plete. A c oncrete b ond beam is po ured for
Straw-clay is the general ter m used for any
... combining earth with natural fibers has
Straw-clay block
the top of the wall on which the roof will
build ing ma teria l that i s mad e out of str aw
led to an unfolding of options and possi
construction of the
sit. Even at its simplest, rammed earth re
and clay (with some sand to reduce crack
bilities that would not be o pen t o us if we
quires more complex technology than
ing and increase mass) but does not fit into
were to remain s imply straw bale builders."
adobe or cob but can be used to raise mas
the traditional adobe or cob category. Al
The main disadvantage of adding fiber
office headquarters for the Save the Children Foundation in Cuidad Obregon,Mexico. Straw-clay can be used
sive walls in a shorter period of time
though the mixture can be very similar to
to an earthen mix is the reduction in the
(Easton 1996).
adobe or cob, the main difference is the
material's thermal properties. The more
construct whole walls,
greater quantities of fiber. If the binding
straw, the less thermal mass the structure
wall or ceiling infill
clay is diluted with mor e water to a creamy
will have. This is only a disadvantage if the
In Britain, wattle and daub was widely
liquid consistency prior to mixing with fi
surface is needed for passive solar heat gain
used in the construction of internal walls
bers , it becomes "light clay." The most
or cooling, in which case less straw and
inserting bamboo or
and ceilings and also for external walls of
popu lar uses of s traw-clay mixes includ e
more sand can be added to the mixture.
branches as
houses. Wattle-and-daub panels in tim
straw-clay blocks (straw coated with light
ber-f ramed houses were in com mon use
clay rammed into formwork), thin interior
W A T T L E
AND
DAUB
between framing or floors, large ceiling panels made by
reinforcement, or even rolls and arches.
PAPERC RETE
or exterior walls reinforced with bamboo
"Papercrete," or "fibrous cement," is an ex
The wattle (branches) act as suppo rt for
or branches, ceiling infill between beams
peri ment al techn ique recently reinve nted
mud plaster (daub). Oak or other timber
or floors, or straw-clay panels for ther mal
stakes are installed vertically into a frame
or acoustic insulation. Higher density of
woven out of willows or other flexible
straw allows for better insulation for roofs,
wood and covered with a heavy mixture of
floors, or the insulating layer on an
until the eighteenth century.
to make large blocks to
independently and pioneered by Mike McCain in Alamosa, Colorado, and Eric Patterson of Silver City, New Mexico. Papercrete is a type of industrial-strength
EARTH
ARCHITECTURE
12
papier-mache used to make large blocks to
10 percent cement. This mixture is then
This method of construction is rising in
construct houses as well as a plaster for
poured into forms to make blocks and can
popularity among natural and alternative
earth. Earthbags can be used in areas with
builders, especially in the United States.
limited technology and low income, but where people are willing to work on con
covering them. It has been successfully
also be used as a plaster or mortar.
intensive than adobe, cob, or rammed
used in earthbag projects as a thick plaster.
In Adobe Journal (nos. 12 & 13) Mike
This technique is essentially a flexible-
If applied in several 2-inch ( 50 millimeter)
McCain described a procedure for making
form variation of rammed earth. The bags
structing buildings for themselves. The
layers, papercrete will contribute to t he in
large quantities of papercrete. Fill a tank
are permanent forms that allow you to
bags are cheap and easily transported, so
sulation value of an earthbag house. Ac
with water and add magazines and news
ram or tamp the earth to create thick
this technique can be used for disaster-
cording to Gordon Solberg in an Earth
paper. Start mixing, and when the mixture
earthen walls, symmetrical arches, vaults,
relief housi ng.
Quarterly special issue on paper houses
turns int o a slurry, add 8 to 9½ one-gallon
or domes, and freeform landscape fea
(see the bibliography), papercrete's R-value
buckets 2/3 full (or 6 shovels-full, approxi
tures; and to sculpt forms the way a potter
is 2. 8 per inch. When dry, papercrete is
mately) of sandy soil that has been sieved
molds coils of clay, blending your struc
lightweight, holds its shape well, and is
using
ture into the landscape.
remarkably strong. Papercrete is also du
rocks. Then add one 94-pound bag of ce
The earthbag technique requires few
rable when wet, although not waterproof,
ment to the mix. The amount of water
skills and tools other than a shovel, and
and in very damp climates will need to be
needed can be estimated by watching as
can be used on almost any land, in any lo
sealed with a waterpro of layer. For in
the cement is absorbed by the paper fibers.
cation. When built properly, earthbag
stance, a coat of tar has been used success
Be sure that the water is evenly distributed
walls are extremely strong. They are most
fully as waterproofing on top of a paper
though out the mix, as any excess water will
advantageous in remote areas with no
crete structure in Colorado.
separate. By weight, 20 percent of the mix
wood for a frame and no clay for a cob or
To make papercrete take a large mixing container and soak old newspapers and magazines until they are soft. Mix in ce ment or lime and sand for greater strength. The recipe for the papercrete plaster mix
chickenwire
to
eliminate
larger
ture should be one-half sand, one-quarter
adobe building, since the use of bags as a
paper, and one-quarter cement, and the
container allows the builder to utilize a
remaining 80 percent of the mixture
wide range of soils, from unstabilized
should be water. Mike has devised a faster and easier way
earth or sand directly from the site to soils
of mixing by mounting a barrel with an
a result, costly materials such as cement
chapter 8) is as follows:
overturned lawnmower blade in the bot
and steel can largely be avoided. Earthbags
paper to 1 part cement + water Second coat (more waterproof): 1 part
cement to 1 part lime to 8 parts sand
Plan
with a high clay content, or even gravel. As
Kelly and Rosan a used on their ho use (see
First coat (more insulative): 1 part
Sketch view.
tom above the axle of a cart. He uses a drive
can even be used in areas prone to flooding
shaft to turn the lawnmower blade when
and periodic wet conditions.
the wheels of the cart turn. The mixer can
If an arch is used as the primary struc
be towed behind a car or truck, or even a
tural element—for example, a dome for
horse.
the central structure with self-supporting
EARTHB AGS
sary in the construction, thereby avoiding
Interconnected spaces can be arranged in response to the site and solar exposure.
arches for openings—no wood is neces
+ water To make papercrete blocks for con
Earthbags are textile bags or tubes filled
the deforestation so widespread in the
struction, Gordon Solberg recommends
with earth (sometimes sand or gravel),
United States and around the globe.
mixing together a "soup" of 60 percent pa
rammed to a very solid mass, then used to
per, 30 percent screened earth or sand, and
construct foundations, walls, and domes.
Earthbag buildings are low in materials cost, but intensive in labor, albeit less labor-
Roof plan.
EARTH
14
ARCHITECTURE
15
An earthbag "dome" is round ed overall,
required. Such structures grow organi
raid shelters; and by landscapers, to create
ersidad Francisco Marroquin in Guate
but not necessarily symmetrica l. The height
cally, each addition buttressing the next
free-form retaining or enclosure walls.
mala, which attempted to develop an
of the dome proportion ally exceeds its di
one. Chapter 2 explains the principles of
According to J. F. Kennedy (1999, 82),
earthquake-proof system. Long cotton
ameter. The difference between earthbag
arches, domes, and vaults that you will
German architect Frei Otto experimented
tubes, dipped in lime wash to prevent the
domes and the high-tech geodesic domes
need to know to build these structures
in the 1960s with using earthbags for
bags from dete rior atio n, were filled wi th
invented by Buckminster Fuller is that
with earthbags.
buil ding . In 1978 a team from the For-
volcanic earth (pumice) and stacked be
earthbag domes can never have large
Through recent history, sandbags and
schungslabor fur Experimentelles Bauen
tween bamboo poles, serving as a proto
spans. An earthbag house can be anything
earthbags have been used for varied pur
(FEB), the Research Laboratory for Ex
type for a single-story house. The poles
from a single dome to a whole village of
poses, most ly in emergency relief work, for
peri ment al Buildi ng at the Universit y of
were tied with wire every fifth course and
domes interconnected by vaults. Arched
example to provide erosion or flood con
Kassel in Germany, led by professor, archi
fastened to the foundation below and a
openings can form entrances into other
trol, when filled with earth or pumpe d full
tect, and author Gemot Mink e (Lehm bau -
bon d beam above, creatin g movabl e but
spaces, niches, and apses. If a large earth-
of concrete or soil cement, then used for
Handbuch, 1997), set up an experimental
earthquake-resistant walls. Further re
bag h ouse is desired, many dome d st ruc
fast construction of embankments. Earth-
earthbag project. This expe riment was fol
search was carried out by Minke at the
tures can be built, each one joined to the
bags have also been used by archaeolog ists,
lowed by a joint research project spon
university through extensive experiments
next using a small vault. New openings can
to aid in structural support of collapsing
sored by the FEB, the Center for Appropri
with earth-filled sacks and tubes to create
be easily cut o ut an d extra ro oms a dded as
walls; by armies, to create bunkers and air-
ate Technology (CEMAT), and the Univ-
various structures, including domes.
B
etween 1993 and 1995, three of the experiment al earthb ag structures at Cal-Earth passed structural tests approved by the International Conference of Building Officials (ICBO), leading to a building permit for the Hesperia Museum and Nature Center in California in
March 1996, the first to be granted u nder the California Building Code for earthbag const ruction.
A school initially designed by Nader Khalili and lliona Outram in Nevada is currently under
wrap aro und the buildi ng rather than lifting it (Muller 1993). By contrast, vaults have a very poor earthq uake resistance. This is due to the torque oscillations in structures, caused by the strong increase in seismic accelerations transferred from the terrain to the founda tions when at different levels the centers of gravity do not coincide with the center s of torsion ( Hoube n and Guillaud, 313). For seismic areas, Nader Khalili has developed a foundation system where the base of
construction with code approval (Outram 1996). The tests carried out for the ICBO included a live-load test and dynam ic and static-loading tests. For some of the tests, cables were wrapped around three buildings of different designs, and hydraulic jacks were used to pull 3,000 pounds of cumulative pressure every 15 minutes. Nader
the dome is isolated from the slab it sits on by a layer of sand, therefore enabling the structure to move freely during an earth quake, (see chapter 3 for more on foundations).
Khalili explains, "On our superadobe prototype we went from 3,000 to 26,000 pounds of continu ous stress and held it there for hours. This was beyon d any required cod e for any building with in fifty miles. The inspectors foun d no cracks or movemen t, so now this method is app roved for all types of buildings, from residential to comme rcial."
(designer/builder
Jun e 1996.)
In high wind and earthquake areas, symmetrical buildings tend to be less heavily damaged.
Above: In 1993 the sandbag and barbed wire system was analyzed at Cal-Polytech, San Luis Obispo, where testing included observ ations on a scale model on a seismic table (Outram 1996,58).The earthbag structures tested were constructed out of unstabilized earth, with barbed wire between each course, an adobe plaster finish inside and outside, and metal strapping loosely netted about the structure to contain bursting forces. The
The form of a dome is more likely to absorb an earthquake's jolts and spread the shock equally
intersections were riveted or bolted together, and four zones of diagonal "X" strapping were added for
through the structure, and the weight and curve of a dome deflects winds, allowing them to
resistance to shear forces (Kennedy 1994, 19).
EARTH
16
ARCHITECTURE
17
The recent trend in using earthbag tech
Kaki Hunter and Doni Kiffmeyer of OK
rial (meaning it contains little binding
nology in building homes is largely due to
OK OK Productions; a three-vault house
strength such as clay) the stronger th e bag
Cut the bags with scissors or a scalpel, and
the pioneering work carried out by the
built by Cal-E arth apprent ices in Sar-
material mus t be. If the soil has a high clay
scoop out the hard, rammed earth. The
work can be hacked off, exposing the bags.
Californian Institute of Earth
miento, Mexico; a development built by
content, bags might not be necessary to
bags can then be resealed using nails like
Art and Architecture (Cal-
Mara Cranic in Baja California; a two-
contain the earthen mixture (see the dis
tailor pins or sewn together with wire, and
Earth) in the Mojave Desert,
story house, the ground floor constructed
cussion of soil testing in chapter 7 ) . In that
the plaster reapplied. This is a time-con
which was set up by Nader
of earthbags and the first floor of timber,
case, other construction techniques such
suming process, and care must be taken
Khalili, Iranian-born architect
built in the Bahamas by C arol Escott and
as adobe or cob might be more appropri
that the opening cut out is in the shape of
and author, who calls his build
Steve Kemble of Sustainable Systems Sup
ate. When earthbags are used, especially in
a steep arch for structural stability (see the
ing technique "Superadobe."
port ; a h ybrid earth bag a nd pumice -fille d-
flood areas, care must be taken that the
discussion of openings in chapter 4 ) . If a
Since 1 9 9 0 , the team at Cal-
bag h ouse built by Kelly an d Ros ana H art
lower courses of the wall do not contain
square opening is cut out, the ope ning will
Earth, in collaboration with
of HartWorks; and Joseph Kennedy's ex
clay, which wicks moisture. If the higher
not support rows of bags above. Square
the city of Hesperia and many
peri ment al wor k in S outh Africa with bags
courses contain clay, they need to be
openings must therefore be the height of
researchers and associates, has
containing high proportions of clay, ce
tamped or r ammed well to reduce the like
the whole wall. Better yet, plan ahead and
been
ment bond beams, and bag additions to
lihood that insufficiently compacted clay
build in arched openin gs that can be ac
existing structures.
will absorb moisture.
investi gating
earthb ag
construction and developing
cessed later by removing the finish plaster. The cheapest and most flexible option is to
its applications, from straight
Earthbags are also becoming popular
walls to domed structures. To
among natural builders as foundations,
EXT ENDI NG
satisfy a desire (or even an ob
filled with gravel, sand, and/or earth, be
BUILD ING
not be afraid to start small and expand
session) to avoid wood, they
neath straw bale and cob buildings. Earth-
It is helpful to plan for future extensions of
later.
have managed to create stable dome-
bag stru ctur es can range from emergen cy
an earthbag building during the initial de
An earthbag structure can also be com
shaped structures using the corbeling
refugee housing for the poor to elaborate,
sign stage in order to prevent awkward re
pletely recycled. I f the bags were filled with
interior plaster. Though
method (see chapter 2 ) . This means that
modern residences complete with plumb
design problems later and to avoid the
pur e earth from the land the buil ding is
the polypropylene
with no materials other than bags, barbed
ing and electricity.
need to rethink all the openings and utili
standing on, once the structure is no
ties. For example, anticipating a future
longer maintained the walls will begin to
opening by building an arch in that loca
turn back into earth after a few decades,
An experimental dome at Cal-Earth, has stood for five years without
bags have degraded from ultraviolet light,
wire, and local earth, you can build your
the compacted earth,
self a shelter anywhere in the world.
which has a low clay content, is falling apart as could be expected.
W H E N
ARE
EARTHBAGS
OR
REC YCL ING
THE
plan future extensi ons at the outse t. Do
A P P R O P R I A T E ?
tion and filling it in with nonstructural
especially if biodegradable burlap bags
shops at Cal-Earth have started to spread
The bags are used only as a temporary
earthbags or another material such as
were used. If polypropylene bags are us ed,
their knowledge. The first fully function
formwork for ramming the earth, before
straw bales or straw-clay mixture can save
they will only biodegrade if exposed to the
ing and lived-in earthbag dome was built
the plaster is applied. It is actually the plas
much time when you decide to cut
sun's ultraviolet light once the protective
in Arizona for Shirley Tassencourt by
ter that should be considered a permanent
through the original wall to make an addi
earthen plaster deteriorates, which it will
Dominic Howes, who went on to build
enclosure or casing. The materials used to
tion. But if the earth in the bags is
do over time without regular recoatings. If
other round, domed, and straight-walled
fill the bags can range from very loose
compactable and not just pure sand,
an earthbag structure is dismantled prior
or square earthbag houses and water-stor
gravel, pumice, or sand to a more com-
which will simply spill out when t he wall is
to the polypropylene's disintegration, the
age tanks. Many others have followed, in
pactab le soil, whic h mig ht cont ain vary ing
breach ed, it i s also possible to mak e ope n
bags as well as t he e arth inside can be re
cluding a domed structur e built in Utah by
amount s of clay. The weaker the fill mate-
ings later if really necessary. The plaster-
used for a new building.
Many people who have attended work
EARTH
ARCHITECTURE
19
18
the shelter is needed only for a year or two, EARTHB AGS
TLHOLEGO LEARNING CENTRE, SOUTH AFRICA
T
his prototype was designed by Jos eph F. K enne dy and con stru cte d using burlap sacks and soil-cement
plaster, a concrete bond beam, and a brick dome roof. The walls were built using burlap sacks filled with the earth from the site, which had a high clay content . These wer e well
FOREVER
in which case the bags can be left exposed
Many regions in the world, including the
and allowed to deteriorate in the sun.
desert regions of Nort h Africa, the Middle
Another great advantage is that sand
East, and the southwestern United States,
bags have l ong bee n used to cont rol floods
do not have abundant supplies of wood,
and erosion in many areas. This demon
stone, or clay. In Egypt, for example, the
strates the strength and durability of these
traditional
was
walls, suggesting that this material would
adobe made out of clay taken from the
be perfect for flood areas and disaster re
flood plains of the Nile. Now clay is in
lief. The aerodynamic shape of domed
great demand, and therefore more expen
houses that integrate into the landscape,
construction
material
tamped to achieve c ompaction. The bond
sive to acquire. To be able to bui ld with or
shaped like mounds or hills, might better
beam was poured on top of the wall to
dinary sand or unstabilized earth could
withstand strong winds and hurricanes,
benefit many peop le.
whic h the brick dome woul d be fixed. The
Of course, unlike adobe or cob con
first row of bricks to the brick dome was
provi ding ano ther advant age of the se in expensive shelters.
hollow, allowing the insertion of reinforcing
struction, where the earth used contains
Ultimately, my love for the earthbag
rods and anchor bolts to anchor the dome
clay as a binding element, the sandbag or
technique also comes from the simplicity
to the bond be am. The structure has buttresses for added stability and was
Detail of the earthbag house prototype showing the brick domed roof and buttresses.
plastered with soil cement. Sawn bags were also used for shade on the trellis.
earthbag technique requires a source of
of the construction process. There is no
bags, bu t in mo st place s, clot h is an acces
saw or nails in sight, just bags and earth.
sible commodity. These bags can be made
There is no need to lift heavy loads, be
out of absolutely any cloth, even old
cause the earth is carried to fill the bags in
clothes cut up and modified to hold earth.
place. Any child or ad ult coul d build th em
The bags are only there to hold the earth in
selves a house!
place befo re plas ter can be ap plied , unle ss
External planters, also constructed using earthbags.
2
USIN G TO
BASI C ST RUC TU RE S FROM
BUIL D WIT H
NATU RE
EAR TH
T
o be able to build out of earth
When you consider the size of an
alone, we must understand certain
individual termite, photographed
basic s truc tura l princ iples . To m e,
standing alongside his nest, he ranks
the most important structural element,
with the New Yorker and shows a
the key to all earth construction, is the
better sense of o rganizati on t hen a
arch. This was on e of my earliest and most
resident of Los Angeles. Some of the
exciting discoveries concerning earth ar
mound nests of Macrotermes
bags form the upper
chitecture, as the arch is a form that occurs
bellicosus in Africa, measure twelve
part of the dome.
all around us in nat ure, which allows us to
feet high and a hundred feet across,
build stro ng, resilien t stru ctur es with out
[and] contain several millions of
high-embodied-energy materials such as
termite s.... The interiors of the
timber, concrete, or steel. An arch can be
nests are like a three-dimensional
used to form the curved or pointed upper
maze, intricate arrangements of
end of an opening (as in a window or d oor)
spiraling galleries, corridors, and
or a support (as in a truss or bridge); this
arched vaults, ventilated and air
shape is strong and stable because gravity
conditioned. ... The fundamental
pulls equally on each part , and each par t
structural unit, on which the whole
supports the weight of the parts above.
design is based is the arch.
Most naturally occurring caves incor
Facing page: The first earthbag dome attempted at Cal-Earth. Strapped straw-filled
Termites building an arch. Even though they work on the opposite
pora te the arch in their str uctu re. Also,
As Nader Khalili has noted in Ceramic
animals that make dwellings in the earth
Houses, forms in nature, whether con
use this form to prevent their homes from
structed or created by natural forces, ex
collapsing. One such example is a colony
emplify efficiency.
of termites building their earth house us ing the arch as their main structural ele
Nature generates struct ures based on
ment to support a network of ducts and
the principle of minimum material,
cavities, as described by Lewis Thomas in
maximum efficiency. From mol
The Lives of a Cell:
ecules, to soap bubbles .. . all follow
ends, the arch meets in the center. (After Woodwa rd 1995.)
USING BASIC STRUCTURES FROM NATURE TO BUILD WITH EARTH
22
23
this general rule ... a spider's web is a natural structure that
vides ideal compression, evenly distribut
works by ultimate tension, and an eggshell is a structure that
ing the downward, compressive forces
arm of the arch where it begins to curve
works by ultimate compression. Both use the minimum and
along the whole of the arch.
toward the center to meet its symmetrical
the appropriate material with maximum efficiency.
horizontal pressure is the point along the
counterpart, the other arm of the arch. The imaginary line running between these
Over the course of architectural history, the construction of
two points where the curves commence is
roofs and openings o ut of earth alone became a necessity in many
called the spring line. Buttresses should re
regions where structural timber was not easily available. In Egypt
inforce the base of the arch up to this
and the Middle East, among many other places, builders came up with the idea (no doubt emulating na ture) of arched openings and
A chain under tension. Chain turned upside down forms a lancet arch under compression.
spring line or higher. You can calculate the size of the buttress
vaulted roofs to cover the spaces they wanted to inhabit. One can
In a masonry arch using this form, the
needed by drawing a model to scale on
still visit large spanned domes (a set of arches with a common cen
individual bricks are tilted upward at t heir
pape r (see the illus trati on below) . Divide a
tral peak or pivot) and vaults (a series of adjacent arches) in the
outer edges, toward the center of the arch.
curved arch (which could also represent a
Middle East built with adobe that have lasted for centuries. How
Once a keystone is placed in position at the
vault as well as a dome) into three equal
ever, instead of buildi ng large spaces and then subdivid ing them, it
peak of the arch, ver tical force, or gravity,
tangential parts . Project out from Y, using
is often more appropriate in earth construction to build several
pushe s d own, causing the stones to press
poi nt X as the center line of a circle and Y
smaller spaces connected to each other, in order to provide for
against each other and transferring the
as the end of the radius. Measure from
structural stability in each element, a nd to acco mmodate different
load to the ground.
poi nt Z to determine the necessary thick
functions, like rooms in a conventional Western building. This introduction to nature-based architectural forms will
To prevent this downward force from
ness of the buttress.
causing the sides of the arch to kick out
emphasize the primacy of the arch, that singular structural ele
horizontally, thereby collapsing the arch,
ment that enables builders to construct arched openings, vaults,
butt ressin g must be added at either side
and domes. Once you understand the structural principles of the
around the base. The point of greatest
arch, you can create a network of variously sized and shaped Sean relaxing in the opening of Allegra's earthbag garden wall after a hard day of plastering.
arches constellated together to form a variety of useful and beau tiful spatial structures. When the arched form is repeated in linear
How to determine the
fashion, it becomes a vault. When an arch is rotated on its central
minimum size of a buttress.
axis or centerpoint, it becomes a dome. When an arch is laid upon the ground, then partially raised, diagonal to the ground, it be comes an apse.
Because successive arches function as Vertical forces acting on an arch.
often repeated to form vaults, serving as a
A R C H E S
Large-span concrete arch, Arcosanti, Arizona.
butt ressin g, in older b uildi ngs the arch i s
A chain hanging between two posts creates an arch form that is
Horizontal forces
structural and decorative element, as can
perfectly in ten sion , because of equal di stri buti on of gravity along
acting on an arch
be seen in old churche s and cathed rals.
the curves. An arch of this shape is called a lancet or catenary arch.
Other commonl y used buttresses are solid
When you turn this shape upside do wn, you get a design that pro-
buttresses, parapet-tie wall buttresses, and
Another arch acting as a form of buttress.
USING BASIC STRUCTURES FROM NATURE TO BUILD WITH EARTH
24
tie bars. These buttressing systems must be evenly distributed along the vault and se
ing adjacent domed or vaulted structures. In Iran, where earthen architecture is an
curely anchored in the ground.
ancient and ongoing tradition, the most
MAK IN G
is approximately 12 feet ( 3 . 6 meters). Ac
permanent
When learning ab out the forces of the arch
cording to research conducted by the Uni
form used in
and the materials that you are working
versity of Baja California, Mexico, the ratio
with, there is no substitute for actually
of span to length in a vault should be no
commonly found span (or width) of vault
solid buttress
parapet tie wall
tie bars
25
THE AR CH
Detail of the
Obregon, Mexico.
learning through your hands. You can make a small dry-pack arch as an experi
above). This form was constru cted out of a
mental exercise. This technique is called
bamb ooli ke ree d called car rizo, wh ich was
"dry pack" because no mortar is necessary
ben t over a very simple tem por ary form
to hold the arch together. A temporary
and buttressed at the ends with a concrete
supporting form can be made out of ply
beam . T hree layers of carr izo were pl aced
wood , a bucket, or anything else that has a
A repeated arch forms a vault.
circular shape. Balance this form on wedges to ease its removal once the arch is
more than 1.5 meters times the width. If a
constructed.
vault is greater in length, there is a danger
Another example that I have come
As you position stones or bricks on top
that in an earthquake the vault will reso
across of a permanent form for vault con
of the form, place shims (small stones or
nate beyond its capacity to absorb the
struction was in the Hermosillo project
fired brick) between the outside edges to
shock, and will shatter (Khalili 1986, 57).
(described in detail on page 1 4 3 ) . Rein
ensure that t he inside edge of each brick is
Because the walls of a vault are struct ural,
forcement rods were embedded in the
perp endi cula r to the ar ch fo rm. P our sand
openings such as windows and doors
ground at 18 -inch ( 4 5 0 millimeter) inter
between the b ricks to fill any caviti es.
should be kept to a minimum.
vals, then bent into position, and horizon
Once the keystone is in position at the apex or meeting point on top, and the arch is buttressed, the temporary form can be removed.
Construction of a dry-pack arch at Cal-Earth during construction of the Hesperia Nature Museum.
over each other and were finished with an insulative straw-clay mix, capped with a
There are three main methods for con structing a vault.
waterproof coating of lime.
tal members were added. An expomat mesh—a stretchy metal mesh material
The first is to build over a form, which
that can be used on corners, damp-proof
can be removed and reused. This is eco
membranes, or any areas where plaster
nomical for small spans, but the cost of
must be applied to a nonstick surface—
V A U L T S
timber to construct the form for a larger
was then fixed to the underside to hold the
If you elongate an arch or repeat it in a lin
span may be considerable, unless you have
4 inches ( 1 0 0 millimeters) of soil-lime or
ear sequence, the new form created is a
a plentiful local source.
soil-cement that was applied on top. This
vault. The same buttressing rules apply to vaults as to arches (see page 2 3 ) . A vault is
The second method is to use a perma
formed a very sturdy structure. The pho
nent form, built to become an integral part
tographs on page 1 46 show the strength of
simply a deep or extended arch. Vaults can
of the structure. A good example of this is
the arch. The reinforcement bars alone,
be us ed to form the passageways conne ct-
in the Obregon project in Mexico (see
when bent in an arched shape, could
USING BASIC STRUCTURES FROM NATURE TO BUILD WITH EARTH
26
support the weight of a person. Of course,
As with arches, the buttressing for a
the materials were no t entirely ecological.
dome only needs to provide support up to
The third method of making a vault is
the spring line. The buttress can either be
to use no fabricated form, merely earth.
constructed along the outside, or the do me
The Nubian vault may be built without
can be sunken into the ground so that the
any structural members or formwork, just
ground itself will act as the buttress.
An angled masonry arch or dome.
27
A corbeled arch or dome.
using earth-clay-straw blocks or masonry (Houben & Guilland 1994). sive horizontal courses. This is the principal used in sandbag con
The end wall is built up first. This wall is either straight or arched. The first brick is
struction; because the bags have no mortar to bind them and the
laid at an angle, an d others follow suit. The
sand is a fluid form, they cannot be placed at an angle. An earthba g dome could be con structed with the earthbags at an angle if there
vault can be started at either or both ends simultaneously to meet in the middl e. For an in-depth account of this method, see Nader Khalili's Ceramic Houses.
A tension ring.
A compression ring.
Note: A tension ring can be created out of concrete with continuous reinforcement (rebar) at the base of the dome. A compression ring at the top is
A P S E S
necessary only if there is an opening.
were a form underneath, bu t for a dome this could be very expen
A spiral corbeled brick dome under construction at
sive to construct, given the amou nt of material required; therefore,
Cal-Earth under Nader Khalili's supervision.
angling is only practical when constructing arches. Earthbag domes must be corbeled. To build an earthen dome on top of a square-shaped structure,
An apse is a leaning arch. Figuratively, if
squinches need to be constructed first. A squinch forms the transi
you lay an arch on the ground and raise it
tion from square i nto circle. Any shape with even sides could have
at an angle, it becomes an apse. Old c athe
a dome constructe d above. A square is turne d into a circle by cre
drals utilized the apse form for rounded
ating four squinches in the four corners. In this way, a dome can
extensions to the central structure, used as
serve as a substitute for a conventional truss or rafter structure.
more intimate chapels or sanctuaries.
The ground acting as a buttress and a buttressed dome.
Once you understand the "arch principle," there is no limit to the shapes that you can create, and there is no need to be bound by the conventions of rectangular architecture or even by symmetry.
DOM ES
A dome is an arch that has been rotat ed on its central axis to create a group of arches
CORB ELING
with a common peak or center point.
An alternative to the dry-pack arch dis
As already noted, because of the hori
cussed on page 24 is the corbeled arch. Cor
zontal forces tending to push the base of
beling involves cons truct ing the arch in
the dome outward, a buttress or continu
such a way that the units (bricks, stones,
ous tension ring is necessary at the base of
earthbags) lay flat, but each is stepped in
Radius < 500 Thickness
a dome. If an opening is made at the top,
ward so that the weight is evenly distrib
Radius of dome divi ded by the thickness of the shell should not
the horizontal forces will be pressing in
uted along the arc of the arch, as shown
exceed 500.
ward, therefore requiring a compression
opposite.
ring, to prevent the structure from com pressing , or cav ing in.
Like the corbeled arch, corbeled domes are erected by building inward on succes-
* From Philip Vittone."Dome and Vault Engineering," Adobe Journal 12 & 13 (1997): 56.
3
DESIGN,
W
S I T IN G , A N D
hatever materials are used,
FO UN DA TI ON S
range of your own skills. You will also gain
there is no single "right" way
a sense of self-reliance by learning your
to design a house, as land
way through the process.
scapes differ, climates differ, cultures dif fer, and the needs of residents differ. Before
Locating the Building on the Land
finalizing any decisions, research all the
Whatever type of structure you want to
options t hat are available to you. One way
build , how ever larg e or small, it is impo r
of doing this is to take the conceptual de
tant to place it in the context of its sur
sign to a very detailed stage to actually
roundings so that it belongs to the land, as
gauge what materials will be needed and
an integral part of the landscape. Spend as
how the various elements will go together.
much time as possible on your intended
Design is a process of asking yourself ques
site, preferably during all four seasons,
tions, which requires knowing what ques
observing where the sun rises and sets, the
tions to ask.
direction of the wind, the views. Consid er the neighbors, and the simplest routes for
DESIGN
CON SIDERATIONS
Before looking carefully at site prep aration
access, snow removal, power, water, and sewage.
and foundations specific to earthbag con
As much as possible, work around ex
struction, let us consider the basic design
isting elements of the landscape such as
considerations that pertain to any kind of
trees and boulders. Try to minimize the Facing page: Apse and
construction, emphasizing the value of
damage that you will inflict on the land
doing as mu ch of the design as possible by
with even the smallest of houses. Plan to
pumice-bag house in
yourself. By carrying out the design your
replace any vegetation that you cannot
Colorado.
self or in close collaboration with some
avoid destroying. Try to retain the "spiri t"
one who is more experienced, you can
of the place, which is the result of this
maintain control of the materials, keeping
locale's unique qualities and features. You
construction costs to a minimum and the
might want to leave the most distinctive
complexity of the construction within the
areas of your land completely untouched,
dome of the Hart's
DESIGN, SITING, AND FOUNDATIONS
30
31
so they retain their natur al beauty and you
kitchen. If you are building with earth, you
what happens on neighboring sites during
can enjoy them outside t he sphere of your
can sculpt retaining walls, benches, a bread
heavy rains. Talk to your neighbors about
in winter to let the sun's rays reach your
house. Good design will help you mini
oven, or a grotto for gathering out of the
weather patterns and their experiences on
home. Deciduous trees planted on the
the land.
patio s in the s umme r tha t will be exposed
mize your impact on the land, to satisfy
same earthen materials used to construct
bot h t he hu man occup ants and the wild
the house. Creating bridges between out
Building on a hilltop increases the po
the summer but drop their leaves in the
east, south, and west will provide shade in
life, ideally enhancing rather than d isrupt
side and inside is a crucial part of building
tential for erosion. Consider wind expo
winter, allowing more sunlight to reach
ing the natural energy flows in the sur
the house.
sure and the aesthetic consequence for
the house.
your neighbors' view if you build on a
Carefully consider the materials of the
Topography
high, exposed site. Show the same respect
build ing's interi or. Ea rth or stone walls on
Landscaping
Go to your local building department to
to your neighbors that you would like
which the sun's rays fall can absorb and
The landscaping aroun d your house is just
obtain historical flood reports and other
them to show for you. Remember, from
store heat in order to give it back at night.
as important as the design of your house.
information regarding your land. Choose
nature's point of view, most of the time the
Such walls have thermal mass, which evens
Locate the house in such a way that sun
a higher location that is protected from
best hou se is no house.
light to your flower or vegetable garden is
runoff during heavy rains, or build ap
Sandbags are very often used in flooded
roundings , creating balance and harmony.
out temperature fluctuations, retaining the night's cool to keep rooms cooler dur
not blocked by any part of the building. To
prop riat e drain age, co ntou r swells, retain
areas, and the same technology is viable in
ing the following day, and retaining day
be sure tha t the garden is accessible and
ing walls, or gabions to rechannel runoff
a house, where instead of merely using the
time heat to keep a home warmer even on
inviting, create an easy path to it from your
around the site to planted areas. Observe
bags as a ba rrier t o water, the y can be used
cool nights. Eart hen walls can be beneficial
for constructing a flood-resistant founda
in either hot or cold climates.
tion or first story (see diagrams on facing page.)
If your land has a history of flooding and you plan to build using earthba gs, you could build your house in such a way
An earthbag dome for flood areas. Bags below flood level are filled
Orientation
Consider the location of all windows in
with gravel to prevent capillary
that the main living area is on a higher level, with the
relation to the su n—where it rises and sets,
rise of moisture. Note also
lower level providing a foundation of bags filled with
the waterproof layer
the winter and summer angles, and the
permeable gravel or perhaps an earthbag basement with g ood dra inage for runoff. To preven t wicking
separating the lower from the upper courses.
Orientation of the
shade cast at different times of year by sur
house toward the
rounding hills, trees, or other existing or
south provides passive solar heating in the
pote ntia l b uild ings. If you live i n an area
of moisture from lower to upper sections of
winter. Overhangs limit
that is sunny but has cold winters, adopt a
the walls when water is standing in the
solar gain in summer.
passive solar design to take advan tage of
lower part of the house, the walls should incorporate a moisture barrier to
summer
damp-proof course
the winter sun. Especially in cold climates, avoid building on dark, damp northern
separate the solid-packed flood level
earthbags above from
slopes. (See the bibliography for recom
If you live in a cooler area, you will want
those containing gravel to
mended books explaining the principles of
to shield your house from cold winds. This
facilitate drainage.
passive solar sitin g, design, a nd materi als.)
can be done by positioning the building
Use seasonal screens to create covered
below a hil ltop or be hin d de nse tre es a nd
DESIGN, SITING, AND FOUNDATIONS
32
33
by landsca ping s o tha t foliage or other b ar
to live "off the grid," providing your own
Think of all the activities that might be
riers provide protection. Locating a mini
electricity, heating and cooling, and hot
perf ormed inside and outs ide the hous e
mum of windows on the windward side
water with solar or win d energy. With ac
during all twenty-four hours of the day,
Precision in the laying out of a building's
SITE
PREPAR ATION:
SETTI NG
OUT
can also help considerably during those
cess to a year-round stream, you may even
from when you get up in the morni ng until
base is mos t imp ort ant for locati ng the
windy winter days.
be able to harves t hydroel ectric ity with a
the next morning. Try to think of all the
foundation in the best possible place. If
microturbine sized for household needs.
seasonal changes in light, temperature,
the earthbag foundation stem wall will be
If you are building in a hot and humid climate, it is important to position the
Even in locations where the winters are
smells, insects, the rain and snow, and the
short and another building technique will
house in the pat h of the prevailing breezes.
cold and long and hours of daylight are
views. The more time you spend on the site
be used on top of this—f or example , a
If heavy trees block the wind's path, it is
short, heat that comes free from the sun
before b uildi ng, t he easi er it will be to an
straw bale wall, a timber frame, or a roof
good to raise the house and expose it to
can result in significant cost and energy sav
ticipate its changes. Effective design pro
type such as a vaulted, flat, or pitched roof
the breeze, with openings that go right
ings. As emphasized above, a well-designed
cess involves imagining the countless func
that relies on a level surface—it's essential
through the house (see Steve and Carol's
passive solar hous e can be heate d almos t
tional and aesthetic possibilities as well as
that the foundation provide a level plane.
house, profiled on page 1 3 1 ) . In the hot and
entirely by solar gain with a small wood-
the limitations of the materials you will be
If you are building a monolithic earthbag
dry climates of the Middle East, cooling
bur nin g or fossil-fuel hea ter as a back up.
working with.
structure, the foundation will be an inte
Building Shape
Planning Ahead
the shape and size of the foundation will follow through the whole structure.
gral part of the walls and roof; therefore
traditionally has been achieved by con structing cooling towers that direct mov ing air right into the living spaces. Also
Think of your hous e not just as a shell of a
Position your house to accommodate fu
plan for overhan gs to preven t too much
box or a dom e, with all of its useful fea
ture additions, including outbuildings,
sunlight entering the house.
tures on the inside. Remember that highly
without drastic modifications of the land
functional external features such as walls,
scape. Also consider the ways that future
porch es, and benche s provi de sun and
changes made by neighbors may affect you
shade zones in summer and winter. I f your
over time. If there aren't any neighbors,
finish will be prone to erosion from
plan for the worst (a future neig hbor
weather, elements such as landscaping,
might build a high building right against
overhangs, and seasonal rain- and wind
your boundary), and you are less likely to
screens are essential, as well as splash-back
be disa ppoin ted.
prot ecti on at th e base of walls. Should the house be one large structure
As much as possible, it is helpful to identify and plan your prospective exten
or a cluster of smaller ones either built si
sions of the house during the design stage
Utilities
multaneously or added on as the need
to prevent awkward redesigning and re
At the earliest stages of planning, identify
arises? A house does not have to be one
construction in the future. Anticipate the
the location of any existing utilities, and
structure. You could start off with the
need for additional services and openings.
consider what services you may need in
minimum living space and utilities and
If you've planned ahead well, as a family
the future, including a spring or well, cis
gradually add rooms, guest houses, and
grows and more rooms are required, these
terns for harvesting rainwater, and gray-
workshops. As the family grows or your
can be added with minimum cost, so do
water and septic systems for processing
needs change, more rooms or structures
not be afraid to start small and expand
wastes. In many countries, it is n ow viable
can be incorporated.
later, if necessary.
DESIGN, SITING, AND FOUNDATIONS
34
The site should be cleared and leveled
35
inscribing the dome, and throughout the
prio r to settin g out lines for t he found a
dome's construction. The compass can be
tion and walls. If a conventional rectangu
very simple, merely a string or a chain, or
lar building is to be constructed, set out
more complex to serve as a guide through
string lines in the traditional manner (see
out the process, allowing the builders to
the diagram on page 3 3 ) ; at the corner
maintain symmetry as the height of the
poin ts where stri ngs cross, ha mmer a stake
structure rises. A more detailed explana
into the ground. If the strings are placed
tion of how to use a compass to maintain
level with each other at a specific height,
the shape in dome construction will be
they can be used as a benchmark to mea
found in chapter 4, "Building with Earth-
sure the height of the stem wall or the
bags." If organic mate rial is remove d, all of
depth of the foundation trench.
the subsoil taken from the foundatio n area
buil ding a sta ble base; to h old th e build ing
situations, the lower courses of earthbags
can be saved to fill bags.
in one integral unit, especially in earth
should be fille d with gravel, up to at least 12
If you are building on a sloping site, the strings should be at the same height as the top of the stem wall.
FOUNDA TIONS
Two scenarios, with good and bad foundation details. On the left, lower bags are filled with gravel, which drains readily and prevents moisture from deteriorating the high-clay-content wall above. On the right, clay in the lower courses is worn away by rainsplash,forming cavities.
quake areas; and to keep the building dry,
inches (3 0 cm) above ground level, with
prov idin g a b arri er bet ween the wall s an d
the upper course very level to receive fur
any ground moisture.
ther courses filled with earth or any other
A circular building or a dome requires a
The functions of the foundation in any
compass to begin constructi on. String lines
buil ding are to minim ize any movem ent
The connection of the wall to the
are not appropriate for this shape. The
of the ground over time; to spread the load
ground is one of the most important de
When constructing an earthbag build
compass will be useful in "setting out" or
of walls and roof evenly in order to give the
tails on an earthen house. When con
ing in a dry area, not prone to excessive
material.
structed poorly, the wall may not last as
moisture or flooding, it is best to build it
long and will jeopardize the rest of the
sunken into the ground. This has several
buil ding . If the foun dati on is not buil t
advantages:
earthen walls and therefore the entire structure.
• the earth that is dug out can be used for filling the bags; • the ground acts as a buttress;
When digging the foundation trench, it
• the building will sit much lower on its
is necessary to go down to undisturbed
site, so it will be less obtrusive visually,
ground, below t he frost heave level to bed
and less exposed to severe winds and
rock or compressed subsoil, to minimize
weather.
any movement caused by the ground. Setting out a round base house using a string as a compass. A compass designed by Nader Khalili to construct caternary-shaped earthbag domes for the Hesperia Nature Museum.
Once this solid ground is reached, you can buil d the foun dati on using gravel in a
Option 2 In a dry location,
carefully, moisture will migrate up the wall through capillary action and weaken the
earth on the side)
When building above grou nd level, you will need to provide separate buttressing.
trench or in the bags, to raise the building's
In damp areas, if the fill material for the
base above gro und level, and to preven t
wall constructio n is high in clay content, it
capillary moisture movement. In most
needs a foundati on base with either gravel
buttressing is provided by digging a hole so the building is sunken into the ground. Excavated earth can be used for fill.
DESIGN,
SITING, AND FOUNDATIONS
Earthbag foundation for well-drained areas with base isolation for domes and a solid "pad" or "raft" with tension ring reinforcement. Pad can be pumice-crete, lime, or reinforced concrete. Gravelbag foundation for dry areas.
Earthbag and gravel trench foundation with dampproof membrane for slightly damp areas.
Gravelbag foundation and buttress for domes in fairly dry areas with sandy soils and good drainage. (Otherwise use perforated drain in gravel trench.)
Gravelbag foundation for slightly damp areas, without the use of
Wider foundation for straight-walled house with
damp-proof
timber posts tied together with polypropylene or
membrane.
Grave] trench and gravelbag foundation.
wire.
1. Exterior finish: earthen plaster, in damp climates
4. Bags filled with earth from the site, well tamped. If
7. Large stones used for a plaster stop.
capped with lime.
the soil contains much clay, it needs to be more solidly
8. Well-consolidated, washed gravel in trench, to
migration upward. Can be larger stones topped with
prevent capillary rise of moisture.
small gravel. The best gravel is rounded to increase
2. Interior earthen plaster.
compacted to minimize its"thirst"for moisture. Compaction of the clay reduces its ability to draw in
3. Four-poinl barbed wire or branches of a thorny
moisture and consequently expand.
according to requirements (this layer can contain
plant. This creates friction and therefore acts as a Velcro-type of mortar between the bags. Note: For added stabilization of straight-wall construction in earthquake areas, the courses of bags can be pinned to each other or can be buttressed or sandwiched
9. Well-compacted earthen layer. Depth varies
5. Bags filled with gravel (well tamped) to raise the structure off the ground, to minimize moisture
radiant floor heating, but needs to be the necessary thickness for effective thermal mass).
migration upward into the wall through capillary action.
10.lnsulation:straw-claymixture,pumice, orperliteclay mixture; depth varies according to climate.
between wooden or bamboo posts tied to both the
6. Waterproofing: can consist of a layer of clay or any
foundation below and the bond beam above.
other waterproofing membrane, or just wellcompacted earth in very dry areas.
11. Well-consolidated gravel, to minimize moisture
drainage spaces around the stones. 12. Pumice- or cement-stabilized lower course of bags, with a continuous ring of reinforcement in earthquake areas. 13. Drain to collect any water that may be trapped (to be approximately 1½ inches (4 centimeters) off the base of the trench to reduce blockage. 14. Waterproof membrane.
DESIGN, SITING, AND FOUNDATIONS
38
39
into an earthbag stem wall for added anchorage, and rubber tub
or "sandy" fill. Otherwise, if the bags con
stabilized by cement, or actually with con
taining clay are exposed to water from
crete, although concrete is expensive, envi
ing or metal rods can be left extending from an earthbag founda
flooding or even "splash back," the clay can
ronmentally destructive, and its use un
tion to allow for compress ion of the adjacent bale wall.
expand and break apart the wall or dissolve
dermines ma ny of the advantages of using
Retaining walls can also be built with bags, but it is imp ortant to
and seep out, leaving cavities and resulting
the comparably inexpensive earthbags as
provi de good draina ge behi nd the wall and ensur e that bags are
in instability. Alternatively, line the foun
an alternative.
prope rly secu red agai nst sl ippage. For added stabili ty compa ct the bags at a slight angle toward the eart h b ank. In addi tion , many
dation trench with a plastic sheet to serve
To construct a foundation with insu-
as a damp-proof membrane that will pre
lative properties, you can tamp the lower
other low-cost foundation systems can be combined with earth-
vent moisture in the ground from migrat
bags full of scoria or pumi ce and wrap
bag or othe r wall systems. Following are a few sug gestion s. Also,
ing upwards into the wall above. Or wrap
them with a damp-proof membrane, since
The Last Straw magazine published a special issue on alternative
each bag in the lower courses individually
small-sized particles tend to absorb mois
foundations (no. 16, 1996; see the resources list).
in a plastic bag before tamping it into place
ture. Alternatively, the pumice can be
(see the description of the Kaki Hunter
mixed with cement to form pumice-crete.
Earth-Filled Tires
Tires rammed with
and Doni Kiffmeyer project in chapter 8).
For earthquake areas, Nader Khalili's
This rammed earth technique is similar to earthbags but uses re
earth.
If the area is not so damp, gravel in the
solution was to isolate the base of the
cycled tires as the permanent forms. Soil-filled tires are stacked
trench and gravel in the lower courses of
structure by laying down a layer of sand
like giant bricks to form foundations as well as exterior and inte
bags will facilitate draina ge, mini mizi ng
between the found atio n slab or the bed
rior walls. To construct a tire foundation, dig a trench down to
rock at the base of the building, allowing it
frost depth, and place tires, ramming th en with slightly moistened
If your house is in an area prone to
to "float" during earthquakes, "like an up
earth, or dig a trench below frost level, fill it with well-consoli
flooding, the lower courses might require
side down teacup." This would reduce the
dated, washed gravel, then level the surface. Place recycled tires on
stabilization with an additive such as ce
risk of breakage in the walls, as no rigid
the gravel and ram them full of moistened earth. Concrete may be
ment or li me. Better yet, design the house
press ure p oint s are ex erted u pward by th e
the movement of moisture upward.
to alleviate the problem of moisture alto gether. For example, you can allow the
ground. The diagrams on pages 3 6 - 3 7 show sev
water simply to pass through the lower
eral examples of foundation details. The
level. Remember that if the lower courses
variations are innumerable, as the best so
concrete infill in voids metal grips for wall strapping stabilized earth in top row of tires
used to fill the voids between tires. Sometimes a concrete sill is pour ed i nto forms on t op, w ith m etal ancho r bol ts embe dded for fastening down the base of the wall above. This met hod of attach ment is not considered adequate in earthquake regions.
rammed earth in tires
Tirefoundation with metal
are filled with coarse sand and/or gravel,
lution will differ slightly for each type of
Rubble or M ortared Stone
which drains very readily, the house is not
earth, climate, construction material, size
This type of foundation can be made from large pieces of stone or
likely to have its foundation washed out
of structure, and budget.
handles.
concrete rubble recycled from old pavement. A trench is dug, then
from underneath (see sidebar on pages
Earthbag or gravelbag foundations can
large rubble pieces are carefully laid on undisturbed ground, with
36-37). Be aware that many "bag" materi
also be used for other natural wall systems,
bent metal rods pro tru din g to pr ovide atta chme nt poi nts be tween
als are subject to decay, and should not be
including straw bales, rammed earth, cord-
the wall and foundation. A rubble trench can provide good drain
relied upon to contain nonstabilized fill in
wood masonry, and adobe. Especially in
age if necessary.
perm anen tly or frequentl y wet cond itio ns.
earthquake regions and when combining
Mortared stone/rubble
To secure the lower course of earthbags
earthbags with straw bale or cob construc
footing with metal
tion, rebar or other pegs can be pounded
grips for wall strapping,
from decay, you may fill the bags with soil
if required.
40
DESIGN, SITING, AND FOUNDATIONS
41
the mixture until it sets. No additional Gabions
A gabion is a latticework container woven out of willow or galva
When used for wall construction, the pum ice can b e mi xed w ith l ime or clay i n
struction, and insulative and thermal
stead of cement, but this will require a
wall. Like a rubble trench foundation, a gabion will drain away
pro per ties , crea ting very comf orta ble liv
separate foundation to raise the wall above
moistu re very effectively, so it can be used below ground as a fo un
ing conditions, pumice-crete makes a
ground level or a damp-proof membrane
dation or partly above ground as a stem wall, isolating an earthbag
good foundation, and some people are
to prevent moisture wicking up into the
Dry-stone
This type of foundation involves great artistry and requires a gen erous supply of relatively flat stones. Many traditional buildings in stony locales have foundations of this type. Carefully selected stones are stacked on top of each other in overlapping courses, resting on undisturbed or well-tamped earth that is below the frost line or any ground movement. Pumice-cre te
This building technique invented by Tom Watson has spread rap idly in areas where pumice is a readily available resource. A very por ou s volca nic s tone , pum ice can be use d as th e aggr egate w ith a mix of a little Portland cement and water to bind it together. A typical ratio is approximately 1 part cement to between 9 and 12 par ts pu mic e, bu t test sa mples always ne ed to b e mad e. For g reate r strength, for example above doors and windows, use 1 part cement to 4 parts pumice. Pumice-crete actually uses very little cement compared with conventional concrete, as the more finely ground pum ice com bine s easily with ceme nt and add s to its bin din g strength. Pumice-crete can be mixed and poured into te mporary or perma nent forms . Due to its porosity, it acts as a good insulative material, needing no further insulation, and also provides thermal mass. Rigid temporary forms could be built in the same way as the formwork used for concrete and removed several days after pour Pumice-crete stem wall.
Due to its low cost, high speed of con
be ren der ed (plas tered ) or unr end ere d.
nized steel and filled with loose stones, often used as a retaining
wall from the moist ground.
Dry-stone wall.
compaction is needed.
ing when the mixture has dried. Permanent forms could be galva nized wire, or any type of bags, paper or plastic, that will contain
constructing entire buildings of this mate
per mea ble wall, whic h could be dam age d
rial. The walls of a pumice-crete house can
by wa ter disso lving the lime or clay.
B U I L D I NG
WITH
EAR TH BA GS
T
he use of the soil-filled sacks called "earthbags" has in re cent years been revived as a building technique, largely due to the pioneering work of Nader Khalili at the Califor
nia Institute of Earth Art and Architecture (Cal-Earth). Its popu
larity is rising for several reasons. It is low cost in terms of tools and materials, utilizing available soil in almost any region, and requiring only a few skills that are easy to learn. The polypropylene or burlap (hessian) bags used to contain the soil can be obtai ned free or relatively cheaply. Earthbag walls go up faster than cob or adobe and are very flexible, unlike rammed earth, allowing the construction of any shape from very straight and square structures to free forms and domes. Earthbag structures can be adapted to any conditions, from regions that flood to the most desertlike lands. When constructed properly, they are strong and d urable, expected to last for hundreds of years. And, because the bags are light and easily transported, they are extremely useful for emergency shelter, in areas that are prone to flooding, or in remote locations where little or no wood, stone, or
A brick dry-stacked corbeled dome.
clay is available. In chapter 2 , we looked at the way that builders using masonry materials can build an arch by angling the bricks or blocks up at the outer edge, since they can be held in place by mortar, which dries solid. An earthbag dome cannot be constructed in the same way as a masonry dome. Due to the fluid properties of earth, each row of earthbags needs to be laid flat, then corbeled, or stepped inward with each successive course, in the same way that a dry block dom e is corbel ed. This corbel ing m akes an earth bag dome much steeper than a masonry dome. The corbeled earthen dome
Facing page: The art of earthbag engineering. Steve Kemble in the Baha mas in 1998.
BUILDING WITH EARTHBAGS
44
takes the form of a lancet arch, as described in chapter 2. If the rows
The width of t he earth-filled bag or tube
complete within three month s, all exposed
of bags have been stepped in too fast, the dome will be shallower in
after tamping will be approximately 13 per
polyp ropyl ene bags shou ld be covered in
cent smaller than the width of an unfilled
some type of finish to protect them from
In this chapter, we will look carefully at the steps involved in
bag or t ube, and t he d epth when filled a nd
ultraviolet rays.
constructing an earthbag structure. Before describing techniques
tamped will be about 30 percent of the
for filling and tampin g the bags that serve as the "building blocks"
original bag width.
its rise and there could be a danger of collapse.
Corbeled earthbag dome buttressed by the ground.
compass point
How to construct an arch of an earthbag dome on paper.
In England, an 18 -inch-wide tube of polyp ropyl ene costs anywher e from 17 to
As a general rule, the lower the binding proper
in this construction system, I will enumerate the recommended
Burlap is a natural woven fabric that is
40 pence per meter, plus delivery fee. In the
ties of the fill, the
materials and tools, then review key structural principles includ
biode grada ble, and therefor e mor e ap
United States, most manufacturers will
stronger the bag
ing the use of tension rings and compression rings, as well as the
pealing to those consciou sly t ryin g to use
deliver a minimum of 1,000 yards at a cost
materia! should
importance of corbeling in a domed structure and buttressing in a
environmentally benign materials. How
of approximately 22 cents per yard, plus
be.
straight-walled structure.
ever, you can only use bur lap if the earth is
delivery fee. See the resources list for infor
not pure sand (which will slip throug h the
mation on ordering polypropylene tubes
MATER IALS
weave of the fabric) but contains com
on a roll.
The materials needed for earthbag construction are relatively in
pressibl e par ticles of soil. Burlap bags are
There are cheaper alternatives, if you
expensive, very portable, and available nearly everywhere. If you
heavier and bulkier than bags made of
are prepared to be resourceful and persis
live in a place where these materials are difficult to find, see the
plasti c, and mo re expens ive to s hip. I n En
tent in tracking down supplies. It is pos
resource list for suppliers who will allow you to order them for
gland, an 18 -inch-wide tube of hessian
sible to use recycled bags, which might be
shipment to your location or use the Yellow Pages to find local
maybe pur chased for anywhere from 30 to
obtained from stores or factories that use
suppliers.
50 pence per meter, plus the delivery fee.
them for bagged produce. "Misprints" are
The material is delivered in rolls of a few
also available for a reduced price from
Bags or tubes: The purpose of t he bag is to retain the earth duri ng
hundred meters, and may be any desired
some companies that manufacture the
the construction process. It is a type of permanent form to allow
width. In the Unit ed States, 18 -inch burlap
bags, a s th ey som etime s make mistakes in
the earth to be placed in a course and tamped solid. When the
costs approximately 50 to 80 cents per
the printing process that render the bags
buil ding is subs equent ly pl astere d over these bags will no longer
yard, plus the delivery charge. For an odor
unsuitable to their clients. Or you can
be v isible, and will be largely red und ant in term s of the ir stru c
less, nontoxic material, make sure that you
make the bags yourself by obtaining inex
tural function, since the plaster "skin" will contain the earthen
get hydrocarbon-free burlap bags (Hunter
pensive cloth or scraps, preferabl y mate
walls. Again, as a general rule, the weaker the mix, t he stronger the
& Kiffmeyer 2000).
rial that does not tear too easily. Fold the
bag s hould be. Bags can come ready-made or can be bought on a roll and cut to the desired length on-site (longer bags are called tubes).
Sculpture made of burlap bags filled with sand.
45
Polypropylene is made of woven threads
cloth in half and sew along one side to
of plastic (Richardson and Lokensgard
form a bag or tube of the desired length. If
1989). Polypropylene is a simple plastic
the bags are filled with a material of high
Chemicalcomposition of polypropylene.
Two types of bags are available on the market: bu rlap (hessian)
and is not as environmentally toxic as the
bind ing p rope rty s uch as clay or stabil ized
and polypropylene, in a range of widths. Both types can be avail
infamous polyvinyl chloride (PVC). It is
soil, the bags can be removed once set.
able in tube form on a roll (usually 1,000 or 2,000 yards per roll),
not biodegradable, although polypropy
or already cut up and s ewn into bags. Presewn bags are generally
lene bags deteriorate if exposed to ultra
more expensive, unless you can find a source for recycled grain,
violet rays, so care should be taken when
used as it comes directly from the site, al
Polypropylene tube on
seed, or coffee bags or "seconds" with some kind of insignificant
storing the material to protect it from di
though if it contains too much organic mat
a roll.
flaw that a manufacturer may be willing to sell cheap.
rect sunlight. If a building project is not
ter or too many large stones that prevent
Fill: The earth used to fill the bags can be
4
6
Four-point barbed wire on a roll.
BUILDING WITH EARTHBAGS
47
good compaction, these need to be sifted
Stabilizers: These are additives mixed with
Tamper: This essential tool is used to tamp
out. The soils can range from high clay
the soil for increased strength, or to fortify
or ram the bags flat once they have been
earthen wall or to beat the bags into any
content to very sandy consistency and may
a finish coating. Typical stabilizers are lime
laid in place. Garden supply stores and
shape desired.
can also be used to flatten the sides of an
include other materials, such as gravel or
or cement. If constructed properly, an
buil ding centers sell manu factu red tam
pumi ce. With clay-rich soils, you could
earthbag structure should require no sta
pers . You can make a metal ta mper o ut of a
consider building instead with adobe or
biliza tion. Cemen t can be u sed for bo nd-
piece of 1-3/16-inch (30 milli meter ) diam
filling of small bags. (To ease the filling of
cob techniques. (See chapter 7 for more
beams and compr essi on rings , for ex
eter metal pipe about 40 inches (1.5
longer bags or tubes, prop a cut-off piece of pipe in the opening.)
A stand: A fold-out stand will aid in the
about clay-based building methods.) If
tremely strong structures that must carry
meters) long welded to a 6-by-6-inch (150-
you're determined to use earthbags, mix
great loads, or for structures that are unde r
by-150-m illimete r) square of metal plate
more sand and gravel into the mix to break
water. Be especially careful when using ce
about ¼ inch (6 millimeters) thick. To
Water source, or buckets for hauling wa
up the clay, or tamp it well and ensure a
ment, which while ubiquitous in our soci
make an even lower-cost tamper, take a
ter: If the soil is too dry, water may be
high stem wall to minimize its ability to
ety, is associated with negative environ
plasti c yogurt cu p, fill it with concr ete mix,
needed to help make an earthen mixture
absorb moisture.
mental impacts. Cement-based finishes
and place a stick studded with nails in the
more compactable. One of the reasons that earthbag construction is very well-
should be avoided with an earthen build
center of the wet concrete, possibly with
Water: This is added to the earth to facili
ing, because cement makes the walls more
rolled-up wire mesh for reinforcement.
tate the tampin g, in order to achieve better
impermeable, and earthen walls must
Let the concrete cure for at least two weeks
compaction. The moisture content of the
breat he over t ime. (The only exceptio n is
before use.
earth should be such that when a handful
on domed s tructures i n very wet climates.)
is picked up and squeezed it holds its
Instead, the finishes can be earthen plas
shape, but you do not see or feel any liquid.
ters with a lime sealant or render. Other
To prevent an excess of moist ure, the ear th
options for finishes on earthbags are dis
mixture can be soaked overnight.
cussed in chapter 6.
Barbed wire: This is used between courses
TOOLS
instead of mortar to grip the bags. Four-
The tools you will need to build with
poin t wire provi des a go od grip ; as a na tu
earthbags are simple and easy to find or
ral alternative, you can use branches of a
make yourself.
thorny plant or jagged rocks or stakes pou nde d into the bags. Barbed wire c an be
Coffee can or shovel: Either may be used
obtained on a coil or salvaged from an old
for filling the bags or tubes. Cans are easy
fence. If the bags you are using are 12
to toss to people who are higher up on the
inches (300 millimeters) wide, only one
wall, but each person will find his or her
row of wire is needed. If the bags are 16
own favorite tool and technique.
inches (400 millimeters) or wider, two rows may be required.
Shovel for digging: A shovel with a cutting edge will make it easier to excavate soil from the site, to trench, or to collect fill.
A heavy block or chunky piece of wood
suited to dry locales is that you can also fill bags w ith dry sand, gravel, or sifted soil. Water level: for leveling the ground. Making a tamper. Left : The tools for
BUILDING WITH EARTHBAGS
wheel has been removed. The caster will
really necessary. However, bags are faster
Plumb line: A plumb bob and line allows
allow for rotation as well as up and down
to construct than cob.
you to check a straight wall for vertical lev-
movement. The caster sho uld be affixed to
If pure sand is used, you must take sev
elness.
a 4 x 4 (100 x 100 millimeter) post planted
eral precautions. The sand must be made
upright in the ground at the center of the
slightly damp to facilitate the compaction.
Wheelbarrow: This is used for transport
dome. At the upper end of the pipe, use
The bags need to be wider to allow for
ing material, for mixing cement or lime
pipe clamps to attac h a guide made of an
into the earth to stabilize it, or for mixing
L-shaped piece of metal.
adobe or cob plaster.
structed using the corbeling method, care PREP ARI NG
Section of earthbag dome showing the compass in use.
THE
FILL
telescoping pole and caster.
needs to be taken that each row does not
Hoe: This may be more practical than a
As I have explained, the bags are used as a
step in too fast. This type of dome can ac
shovel for mixing ingredients.
temporary formwork for the tamped or
tually be much taller than masonry domes,
rammed earth during construction of a
with steeper sides and larger buttresses,
Blade or scissors: For cutting the bags or
buil ding and b efore the plaster is applied .
such as on Shirley Tassencourt's dome (see
tubes.
The plaster finish can be seen as a long-
diagram, page 124). For increased stability,
term sheathing, which if maintained at
it is also possible to tie down one course of
Wire cutters, level, ladder, tape measure,
tentively can be considered "permanent."
bags to the t wo below, creati ng a net w ith
gloves, and tr owel: All of these will prove
The material that goes into the bags can
wire mesh or strapping, or to construct the
useful on any building project.
therefore be of any consistency ranging
dome over a permanent form such as
from very loose—for example gravel,
A construction compass, made with
more stability, more buttressing needs to be provi ded, and if do mes are b eing con
demonstrated in the Malawi project (see
Compass: Required only as a placement
pumi ce, or s and— to a mo re compa ctabl e
guide for the bags in the building of sym
soil that contains varying amounts of clay.
Whenever earthbags are used, but espe
metrical domes, a compass can be as simple
The best fill for an earthbag wall is one
cially in flood areas, care needs to be taken that the lower courses of the wall do not
page 142).
as a chain or a string, or more complex.
with the same consistency as the tradi
When the courses of the dome reach the
tional mix for rammed earth: approxi
contain clay, and are properly detailed to
stage at which they must start to curve in
mately 25 percent clay to 75 percent sand,
shed water (see drawings on page 35). If
wards (the spring line) the compass needs
which will dry into a cementlike hard
bags conta inin g clay are exposed to water,
to be extended after each row. This can be
block. However, eart h seems to be suffi
the clay can either expand and break apart
worked out by making a drawing of the
ciently compactable with as little as 5 per
the wall or dissolve and seep out, leaving
dome, as in the drawing at left and page 44.
cent clay.
cavities that create instability. The higher
An extendable compass may be made
With soil that has a high proportion of
courses need to be tampe d or ramm ed well
with a length of hollow pipe (electrical
clay, it is probably better to consider an al
to reduce the ability of any clay in the bags
conduit will work, or one of those tele
ternative type of constructi on, such as cob,
to absorb moisture.
scoping poles used for cleaning swimming
adobe or one that makes use of other fiber/
Generally, the earth excavated on site
pools ) at tache d at one end to a cas ter (s uch
clay composites; because the clay has bind
can be used for fill. Be sure to remove top-
as those on a grocery cart) from which the
ing properties, a bag to contain it is not
soil and set it aside for a future garden, in -
BUILDING WITH EARTHBAGS
51
50
stead using the subsoil for construction.
only attending to these very general guide
Remove all large stones and organic mat
lines: not too much clay, not too many
ter from the earth mix, as these materials
large or sharp rocks, not too dry or too wet.
too could create cavities later on. If a large
For information about doing soil tests
number of stones are found in the soil,
when building structures that require
sift them out using appropriately sized
more refined sensitivity to soil contents,
screens, and use them as gravel in the
see chapter 7. For information abou t stabi-
lower courses of bags or for foundations,
lization, see chapter 6.
as this nonabsorbent material will drain well and prevent capillary rise of mois
FILLI NG
BAGS
OR TUB ES
ture. If crushed pumice or scoria (a po
Before beginning to fill the bags, make sure
rous volcanic stone) is used for earthbag
the earth is moist enough to allow com
walls, it will serve as both thermal mass
pacti on. Bags may be filled in sever al ways:
and insulation (as in the Hart's house,
with a shovel, tin can, bucket, or whatever
profiled in chapte r 8), but smaller -sized
damp-proof membrane is used, or unless
filled in place. Cans of soil can be thrown
process of filling the bag s. For l andsc aping
up to the person doing the actual filling
or large industrial projects, where time
(see photo on page 5 3 ) . Bags filled by dif
and labor are costly, professional builders
ferent people will vary in thickness, du e to
might use a continuous berm machine,
differences in strength and technique. It is
which extrudes a fabric-encapsulated con
therefore important that one person or
tinuous berm of sand, rock, or native soil
team builds a whole row to minimize the
at a rate of 10 to 50 feet per minute. Filling the bag from
changes in thickness during one course. The rows may vary from each other, bu t as
Filling a Bag with More than Three People
long as each row is of a consistent thick
Two teams can fill a long bag or tube from
ness, this is not a problem. Once a row is
the two ends using the following procedure:
both ends.
water to ease compaction in the tamping proces s. M ore compa cted fill is u ltimat ely more stable. Remember, the soil should be
feet).
2. Fold the edges of each opening back
always stagger the joints, just as in ma
as far as possible toward the middle,
sired length. How long do bags need to be?
If the earth used for filling is totally dry when dug out, it needs to be sprayed with
1. Cut the tube to length (u p to 30
bags in successive course s, reme mber to
Each tube or bag can be cut to the de
discussion of pumice-crete, see chapter 3.)
as shown to the right.
3. When the folding reaches the mid poin t, star t filling the tube from each
If you are building a dome, it is good to
open end. As one person shovels in
have one continuous length all the way
the earth, the other can hold the end
around, unless this wou ld mean a length of
of the tube open and unfold the ends
more than 30 feet, because beyond that,
as it is being filled.
the tube becomes difficult to fill.
moist enough that when a handful is
For the foundation and the first few
picked up and squeezed it hol ds i ts s hape,
rows of wall, it is good to use bags or tubes
but you do not see or feel any liquid , and when a lump of the soil is dropped it falls apart. The soil can also be soaked over
The speed of this m ethod of filling bags on the project in Mexico (see chapter 8)
that are as long as possible to minimize
averaged out to be 25 feet per hour, per
breaks , for str uctu ral stability, but even
team.
small bags that are well tamped can be
night.
used for the foundations. When measur
The appeal of the earthbag method is
ing the required length, add an extra foot
that builders can use such a wide variety of soil and other types of fill for constru ction,
concrete can also be used to speed up the
sonry construction.
the pumice is mixed with cement. (For
tion act as a mortar.
A mechanical pump used for pumping
opening. Bags higher on the wall can be
as keying for the next row. As you stack
which are prone to being damp unless a
bags during construc
the bag.
stays in place and earth is bro ught up to its
strands of four-point barbed wire on top
should be taken not to use too much fine pumi ce or scoria in the lower courses ,
wire placed between
later fold over the surplus fabric to close
never necessary to lift the bag itself: the bag
complete, tamp it well, then place two
particl es can wick mois ture , so care
Two strands of barbed
the person doing the work can lift. It is
of fabric at each end of the bag. You will A team of three filling a long tube in Mexico.
Filling the long bag from one end.
52
BUILDING WITH EARTHBAGS
53
barb ed wire when worki ng on top of a Filling Bags or Tubes with Only One
course that has been keyed with wire.
to Three People
tray to position the first bag
or tube should be filled from only one
If small bags are used, the wall will tend to
correctly.
open end. Once the desired length of bag is
have a great many bag corners sticking out,
cut, shovel or scoop as much material as
which makes plastering difficult, as much
long tube using a plastic
you can lift into the bag, then shake it
more plaster is needed to cover these. To
pipe as the chute.
down to the opposite end. While one per
preve nt this , tuck in the bo tto m corner s as
son shakes the earth toward the end, a sec
the bags are being filled. Utah earthbag
ond person can step on that end to prevent
buil ders Kaki Hu nte r an d Do ni Kiffmeyer
the material from flying out.
"Diddling."
Far left, top: Using the metal
Using Small Bags
When working with fewer people, the bag
Far left, bottom: Filling the
Left: Filling a bag using a stand.
named this process "diddling." When filled,
Or, when working with smaller, more
the open end of th e bags can then be gently
port able ba gs with on e end sealed, you ca n
lowered into place and those corners
shake the material down into the open
diddled as well, tacked under th e weighted
end, and lift the whole bag into position.
end of the full bag.
Once the bag is in place, fold under the
One person can fill small bags by using
open end of the bag to close it. When a row
a stand to keep the end open. Remember,
is complete, this bag should be tamped
the small bags must be laid in a running
solid and flat before the next course is
bon d, with all jo ints staggered. The time
placed on top a nd is ready for barb ed wire.
required to fill small bags for the Honey
Another way to fill bags with a smaller
House project (see chapter 8) averaged
crew is to slide a cut piece of wide pipe in
four bags (approximately 6½ feet or 2
to the open end of a bag, like an ankle in a
meters) per hour, per person.
sock. The pipe forms a chute for the earth to go through. Each time a manageable
TAMP ING
amount is shoveled in, take out the pipe
As noted above, to minimize unevenness,
and shake down the bag. Be sure to avoid
each bag in a row should be filled to its
letting the bag bunch up while it is being
maximum capacity by the same team. To
filled; each load of earth must go all the
create as level a wall as possible, do not
way to the end, with no gaps. A brick can
tamp un til the whole row is filled. Once the
be pla ced un der t he bag t o prev ent creases
whole row is laid, it can be tamped until no
in the bag, or one of the crew can use a foot
movement of th e earth is felt. The sound of
to supp ort the lower side of the bag as it is
the tamping, changes as the earth in the bag
filled. Use a piece of sheet metal or a board
is compacted, becomin g less of a "thump "
to protect feet and clothing from the
and more of a solid "smack."
Below: Steve Kemble tamping an earthbag wall with a concrete tamper in the Bahamas. Inset: Untamped and tamped sides of a wall.
BUILDING WITH EARTHBAGS
54
55
Tamping soils with high clay content lessens the earth mixture's tendency to draw in moisture, but does not eliminate this ten dency entirely. Be sure to avoid having too high a proportion of clay in the earthbags, especially in the foundatio n or lower courses, which are more likely to be exposed to water. You may also wish to tamp the sides of the wall, checking th e • Dam pen the earth prior to filling the bags to improve compaction • In successive courses, stagger all joints between bags, for stability
vertical straightness with a spirit level or plum b line. An advantage of tamping the sides is that then the wall surface will require less
consistency • To minimize une venness , do not tamp until a whole row is complete • In dome construction, tamp each row flat, for stability • Place barbe d wire or other key in material between courses • Buttress all dome s and straight walls
Bench acting as a buttress.
dome, which absorbs the downward hori
the plaster has less surface area to key into.
Ground acting as a buttress.
stabilized rammed earth, metal, or some
zontal forces that otherwise would cause
other resilient material. Since this rein
KEYI NG
the base of the d ome walls to splay out and
forced ring may be the mo st expensive el
• Have the same person or crew fil l the bags for a comple te row or course, for
Reinforced tension ring.
plaster. Th e disad vantag e of a very level or even wall surface is tha t
After tamping, each course needs to be keyed with four-point
collapse. This ring has the same function
ement in an earthbag dome, it may be ad
barb ed wire or br anch es of a tho rny pla nt, whi ch will prov ide fric
as buttressing and is needed in all struc
vantageous to consider buttressing the
tion to prevent any shifting of the bags over time. If no barbed wire
tures in seismic zones and in domes that
structure in areas that do not have seismic
is available, the bags can either be well buttressed, tied to the bags
do not have some form of buttressing
activity (see the diagram series above).
below (see Kelly Hart's pr oject i n chap ter 8), sandw iched b etween
around the base. In most domes, unsta-
A compression ring is the tensio n ring's
wooden poles, or pinned with reinforcement rods. For very wide
bilized materi al may be used in the bags
counterpart at the top of the dome, neces
and short stem walls or landscaping walls, barbed-wire keying is
with which the walls are constructed, but
sary if there is an opening there. It pre
not necessary. Also, on smaller structures, using rough rocks or
in seismic regions the ring aro und the base
vents the dome from caving in because of
chunks of gravel between courses will provide adequ ate keying.
must be stabilized with continous reinforce
If the bags used are wider than 14 inches (350 millimeters), or a
ment surrounded by concrete or cement-
dome is being constructed, two rows of keying maybe necessary. This keying is especially importan t in corbeled domed structu res, provi ding tensile streng th while enabli ng each row to step in slightly. skylight STRU CTURA L
REINF ORCEM ENT
AND
BUTTR ESSIN G
In domes, there are two areas of maximum pressure that require careful attent ion, especially in areas of high winds or seismic activ Buttressing wire. Each row of bags is tied to the two rows below.
concrete bond beam with continuous reinforcement
ity. The base of a dome can be buttressed on the outside with the
Earthbag dome with a compression ring and skylight.
ground, with constructed benches, or reinforced with a "tension ring." The other point of pressure is the top of the do me. If there is any opening at the t op, it mus t be reinforced with a "compression ring." A tension ring is a continuous and rigid ring at the base of the
bags filled with earth
ties on to 3 or 4 rows below
BUILDING WITH EARTHBAGS
56
the upward, inward pressure of that open Buttressing during
ing. Like a tension ring, a compression
construction at
ring needs to be continu ous, made of con
Allegra's house,
crete, metal, wood, or other material con
Arizona.
taining sufficiently sized continuo us rein
Corner of a buttressed house.
forcement. For more complex structures, consult an engineer. While curved walls are structurally selfsupporting, straight walls need additional support. The diagrams on this page show
ways of reinforcing a straight wall with a corner or with connected buttresses. Re member, for stability when constructing If a wall is straight,
intersecting walls and buttresses, always
buttressing needs to
stagger all joints.
Staggered joints at the corner of
OPENI NGS
the Three-Vault
In an earthbag dome, the number of open
House, Mexico.
ings cannot be too many or else the struc tural stability of the dome will be compro mised. The distance between openings should be large enough to properly but Long bags"woven"
If the wall is curved it does
tress the arch that forms each opening. In
into place during
not need buttressing.
general, openings that are square are best
construction of the
suited for square houses; it is possible to
author's retreat.
create small square openings in domes if there is a lintel, but structurally this is not a good idea. During wall construction, where there will be openings, leave loops of wire ex A buttressed wall.
tending out from the strands of barbed wire laid between the bags, which will
BUILDING WITH EARTHBAGS
59
58
allow you to tie off these wires up and down around the opening for added strength. Some builders reinforce their openings with
Size and position of the form used to make an arched
wire mesh, which can also be attached using these wire ends.
opening in a corbeled dome.
There are two categories of openings: arched, which do not need
line of curvature
wood, metal, or concrete as a lintel above, or square, which need lintels, or which utilize a bond beam at the top of the wall as the lintel.
wedge
Arched Openings
If the opening is in the shape of an arch, no lintel is necessary. One way of leaving an opening in t he earthbag wall is to use a form. A
wedge
form can be a circular object such as a wheel, a bucket, or a barrel, or can be specially constructed out of timber in the exact space desired. The opening can also be filled with earthbags that are s ub sequently removed. Several types of arches can be created, some of which are s hown in the drawings and photos. To make the "curved bag" window stabilized bags
shown above, stabilized earth must be used. To make a form, cut an arch in the required shape out of ply
Stitching keystone bags after filling in
Construction of a form to create an arched window
place.
opening.
wood or other flat material and duplicate it, then attach these flat arches to each other with pieces of timber so that the ends are Several demonstrations of creating an opening without the use of a wooden lintel.
parallel . Next, cover th e whole ar ch with pl ywood or o ther flexible,
but this can be expensive because of t he
As you stack the first three rows of bags
sheetlike material.
quantities of materials required. It is less
around the form, add additional perma
Make the form at least 2 inches ( 50 millimeters) wider on each side than the inten ded size of the finished opening, to allow for the thickness of the plaster. When placing the form, make sure to position it on top of wedges, as this will ease the removal of the form after the arch is complete. These wedges could be chunks of timber or tapered log ends. Place a minimum of three well-tamped courses of bags above the opening before removing the form. When building a vault that connects to a structure through an arched opening, the main opening should be located at the end Shirley's dome, showing different formwork on top of the wall.
where the arched opening in the wall has no load-bearing function (see page 2 6 ) . Some builders have constru cted reforms for vaults,
expensive to make a permanent vault out
nent buttressing on either side of the pri
of bamboo or other bendable material,
mary bags to contain the horizontal forces
which the earthbags can be layered
that will act upon the finished arch.
around, or a Nubian vault out of adobe
The arch's "keystone" will consist of the
(see page 2 5 - 2 6 ) . If you do decide that a
last three bags laid in position. These are
temporary vault form is necessary, it is
placed wit h thei r tops still op en, t hen filled
most economical to make one that can be
up with additional earth from above, as
reused rather than demolished.
shown above right. The earth must be
When the earthbag wall reaches the
shoveled into the last three bags simulta
height of the opening's bott om sill, place a
neously, to create the keystone effect. To
form where the opening will be, posi
close these bags, either use nails (stuck like
tioned on t op of wedges to ease its removal
tailor pins through the fabric of the bags),
after completion of the arch.
or stitch the m closed with a piece of wire.
6o
BUILDING
WITH
EARTHBAGS
61
As emphasized above, before removing the form, you must complete the rest of the wall with at least three ta mped rows laid on metal tray
top of the arch.
lintel is pinned to earthbags
Square Openings
Although square openings for windows and doors are not struc turally sound in dome construction, you can incorporate square openings in a straight-walled earthbag building by providing rough framing ahead of time or by cutting them out from the fin ished wall, provided the necessary buttressing is in place prior to this excavating. As shown on page 61 , it is important to add sturdy diagonal
Door frame securely fixed to stern wall
braci ng to all win dow and d oor frames to keep t hem squ are du ring construction. This bracing can be removed once the walls reach
with diagonal bracing. Elevation of doorway.
Section through doorway.
full height. Door frames also need to be securely attached to the foundation for stability. The detailing around window and door openings—for in stance, the seal between a windowsill and the earthbag wall be low—is extremely important in order to prevent penetration of
Below and bottom right: Window details. Always slope the external window sill away from the building with an overhang of at least 2 inches (50 mm) and a drip edge.
moisture. Also note that if a timber frame is used to provide the structure for a building where eart hbags serve as infill, it is impor tant to separate wooden members from the earthwall with a care fully attached waterproofing membrane to prevent moisture pen etrating through at seams between the earthbags and wooden posts and be ams or framed o peni ngs. (See chapt er 6 for more in formation on waterproofing.) BON D
BEA MS
Known in conventional construc tion as a "plate," a bond beam is a rigid structural unit, usually made of wood, metal, or concrete, that sits on top of a wall and evenly distributes the weight of a subsequent floor or the roof. While not relevant to dome construc tion, bond beams are important in straight-walled construction to tie together and stabilize the earthen structu re at its point of great Top: Window in the end of a vault, Mexico.
est outward pressure, especially in areas of high winds or earth
Middle: Stabilized arch, California.
quakes. In additi on to serving as a level platform for a roof, a bon d
Bottom: Arched forms.
window timber windowsill with a drip edge
damp-proof course timber sill plate internal plaster metal lath cement-stabilized earthbag
_ a n c ho r bolt to fixsill plate to cement-stabilized earthbag
Window frame.
62
BUILDING
beam can also serve the fu nctio n of a lintel,
its function, the bond beam can be made
spanning the unsupported gap in a wall
of timber, steel-reinforced concrete, or
created by a window or door. In an earthbag building, depending on
WITH
EARTHBAGS
63
even cement-stabilized earth, well tamped in the bags.
Far left: A bond beam in the Bahamas. Left: A formwork for the bond beam, which will be used as a base for the timber wall plate of the next level.
Below: A conven tional greenhouse in Colorado constructed over a pumice-filled bag stem wall. Inset: Section through the stem wall of the greenhouse showing the wall plate detail.
damp-proof course row of well-tamped cement- stabilized soil papercrete (fibrous cement)internaland external plaster well-tamped gravel bags
ROO FS
T
he roof is one of the most impor
ture, making a house stand out , or can help
tant factors keeping a building dry
a house disappear gracefully into the land
and warm. A good roof protects
scape.
the inhabitants from rain, snow, wind, the
The ideal roof for earthbag walls is one
cold, and the heat. It will shed water away
constructed using the same materials as
from the house, directing it at the garden,
the walls. The main attraction to most
or will catch the rainfall to be stored for
peopl e who discover this build ing tech
later use. The roof can be a dom inant fea
nique is the possibility of using no wood,
adobe plaster with shallow-root plants and grass planted to prevent it from being worn away by rain (only recommended in rainy areas; otherwise the grass will dry out)
Facing page: Cooling tower of the threevault house at CalEarth.
stabilized a dobe waterproof layer two rows of stabilized patties
A grass covering. In rainy climates a waterpr oof
Covering for damp climates (see page 98). The outer
membrane is necessary.
stabilized layer could also be made of papercrete.
Natural roofing materials for earthbag domes.
bamboo or willow wrapped around shingles of grass, overlapping like tiles
66
ROOFS
67
metal, or concrete, as well as the aesthetic value of an earthbag structure. A dome , for instance, is quite an amazing space to be in (some would say "nourishing for the soul") with an option of add ing at least one other floor while retaining its height and beauty. Using a dome or vault is a roof-building technique that is finan cially and ecologically economical if no plentiful, renewable source of wood is available. Concrete and steel contain high em bodi ed energy, as well as being expensive, and earth is a far healthier option. Yet, creating an earthbag dome mig ht not be a solutio n to house design in all climates, nor for every type of budget, culture, or in dividual. The amazing aspect of the earthbag technology is tha t it is genuinely adaptable, allowing each individual to create a house tailored to his or her needs. In many cases it is beneficial to com Detail of a brick dome showing the bond beam.
bine th e eart hbag wall system wit h a flat, pitched , vaulte d, or ot her
V A U L T E D
RO OFS
Ratio of Vault Width to Length
To my knowledge, a vault wider than 5 feet (1.5 meters) has not yet
In vaults constructed out of earth (for
been successfully constr ucte d using earth bags. Most vau lted roo fs
example, adobe), a safe ratio of width to
are constructed from other materials and joined to the earthbag
length should be equal to no more than:
walls using a bond beam. If the soil contains some clay, one way of constructing a small
length = 1.5 meters x width
vault out of earthbags (approximately 3 feet [1 meter] in width,
with the width not exceeding 12 feet (4
which can serve as a connecting space between domes) is by stand
meters) overall.
ing the bags up and placing them in a leaning arch, as shown in the
For lancet vaults, the following ratio applies:
top diagram. Another better way of constructing narr ow vaults is to create a
rise of vault = width/2 + 19.5 inches (50 centimeters)
series of sturdy, self-supporting arches that , when joined together and finished with plaster, create a continuous vault.
roof system, depending on the re quirements. For example, in areas pron e to high levels of rainfall thro ugh out th e year, it is a good idea to combine the earthbag wall system with a more conventional roof type that provides an o verhang to protec t the walls from the constant rain.
Surface finishes for domed earthbag roofs,
BRIC K
OR
AD OB E
ROOFS
to make them water-resistant though not
An earthbag building can be covered with a shallow dome con
necessarily
structed out of masonry brick or adobe in areas where the climate
waterproof:
• lime render or whitewash • cement-stabiiized soil
According to an old recipe I found on the straw bale listserve (http://solstice.crest.org/efficiency/strawbale-list-archive/
• earthen plaster with lime render and
index.html), a cheaper and more beautiful way of waterproofing
In wet climates a waterproof layer is necessary underneath the plaster or painted on top.
creates a narrow vault.
is relatively dry.
• papercrete
whitewash
A series of arches A narrow vertical leaning vault, as constructed for a passageway in the retreat.
straw-clay mix for insulation
carrizo, bamboo, or hazel, or any bundled reeds that can be bent into an arch
water-resistant layer earthbags
exposed bricks than covering them with cement or boards is to: concrete bond beam
Stir 1 pound of finely powdered flowers of sulfur into 8
damp-proof course
straps
poun ds of linseed oil. Bring the mix ture to a heat of 2 7 8
Carrizo and earthen vault.
degrees Fahrenheit, and then allow it to cool. Add some drying oil and paint the bricks with the compound. damp-proof course
For more on waterproofing, see the discussion of finishes in chap
Detail of vault constructed in
ter 6.
Mexico out of carrizo.
timberbond beam anchor bolted to cementstabilized earthbag below
ROOFS
68
69
CONV ENTI ONAL
ROOFS
More conventional roof systems can also
Types of trusses.
W A T E R - C A T C H M E N T
ROOFS
Another supplementary purpose of a roof
be cons truc ted on top of the earth bag
can be to catch rainwater to be used for
walls. The roofs are for areas with high
washing, flushing toilets, watering the gar
rainfall. It is always impo rtant for the roof
den, and even drinking after filtration. For
to have large overhangs (at least 18 inches
directing run-off to a water-storage reser
[45 centimeters] ) on the sides, even the less
voir, a good roof material is zinc-coated
exposed ones. From the standpoint of en
metal, because ethylene propylene diene
vironmental impact, it is better to create
monomer (EPDM)—the synthetic rubber
roofs out of small sections of wood, if
commonly used for roofs, pond liners, and
wood is necessary at all, instead of timbers
water tanks—is apparently slightly toxic.
from old-growth or slow-growing trees.
The water can be collected into a cistern
Wood can be obtained from fast-growing
located either inside the house or out in the
trees in carefully managed forest planta
garden. If it is placed inside the house, care
tions, or builders can use wood-efficient
needs to be taken of its location to avoid its
trusses, laminated timbers, or other engi
functioning inadvertently as a very large
neered wood-fiber products. Trusses can
heat sink, constantly drawing heat from
be pu rchas ed pref abricate d or can be bu ilt
the house's living space. In a passive solar
on-site with local materials. A typical 2 x 4
build ing, the addit ional ther mal mass of
truss provides a great deal of space for in
the water in the tank can help store solar
sulation but does not provide extra living
gain. The water tank should be insulated,
space, unless the scissor truss is used (see
which can be done with straw bales.
top diagram). THAT CHED
ROOFS
A long tradition in England, Ireland, and Wales, thatched roofs are still in use today on
most
cob
buildings.
Throughout
northern Europe, thatch was made of a common reed grass (Phragmites) or tight bund les of straw, usually wheat or rye. Thatch conforms nicely to curved and ir regular roof shapes. The biggest advantage of thatch, in addit ion to its aesthetic value, is that the thatch itself is the waterproofing layer and therefore does not require the
ROOFS
70
addition of any artificial waterproofing
71
This type of roof needs enough rainfall to ensure the watering
materials; moreover, thatch provides suffi
LIV ING
cient insulation. A well-made thatch roof
A "living" roof is one that supports an
do not require wateri ng. Ideally, the roof's pitch shoul d not exceed
can last a long time: straw thatch up to
earthen mulch and plantings of grass,
35 degrees, or the mulch and plants may slide off, especially when
forty years, and reed up to sixty. The main
mosses, or even a berry patch. This kind of
wet or weighed down with snow (it is possible to construct a sys
disadvantage of thatch is that it is combus
roof can be aesthetically pleasing, and can
tem of shelves and n etting to prevent soil slippage).
tible, but the fire danger can be substan
make a house blend in to its surroundings.
tially reduced by incorporating measures
The earth on th e roof serves as extra pro
such as ceilings that reduce airflow to the
tection for a waterproof membrane be
roof, a sprinkler system, or treatment of
neath, and in addition to helping the house
Straw-clay rolled onto
the roof with flame retardant, as discussed
retain its coolness in the heat of the sum
from plywood sheathing or boards to a smooth insulative
long straw, reed, or jute
in Michael G. Smith's book The Cobber's
mer, the thickness of the roof covering is a
straw-clay finish on top of rough surface decking such as
Companion or Michel Bergeron and Paul
sound insulator. Such roofs have also been
carrizo (see figure c left) or previous straw-clay layers
Lacinski's book Serious Straw Bale (see the
known to protect houses from external
(figure a). If plywood or boards are used, and the roof has a
fires.
steeper pitch, it is advisable to create a textured surface to
spanning between rafters. When strawclay rolls are used, no board or mat is
bibl iogra phy).
ROO FS
of the vegetation, or the roof can be planted with local plants tha t
required to support the
The layers of a typical living roof are as follows, starting from the lowest layer which sits on the roof rafters: 1. A layer that creates a smooth surface. This can be anything
Roof trusses coming together in a vortex.
preven t s ubseq uent layers from sliding off (figure b).
straw-clay mix.
Nailin g on s ome 2 x 4 boards, or shaping the straw-clay to create horizontal undu lations , will help (figures b and c). 2. A waterproof membrane such as bent onite clay with a layer of geotextile membrane to prevent root penetration, or polyme r-base d mo dified bit umen , or some othe r kin d o f durable, reinforced, and impermeable sheeting. 3. A cushioning layer of corrugated cardb oard or carpet scraps placed on t op of the w aterp roof me mbra ne to preven t i t A. Detail of living roof
B. Detail showing the layers
showing straw-clay"rolls"
of a living roof with plywood
C. Detail showing layers of a living roof with straw-clay option
for insulation. 1. Rafter
2. Plaster finish. 3. Straw-clay. 4. Long grasses or reeds covered with straw-
clay and rolled up to create an insulating layer. 5. Two layers of waterproof membrane.
1. Insulation between rafters covered with a
to take root in. 4. A layer of soil or other organic matt er 2 to 8 inches ( 50 to
2. Carrizo decking.
20 0 millimeters) deep, seeded with plants. Rock gardens are
3. Straw-clay for insulation.
of course more appropriate in drier climates.
3. Timber batten (50 x 100 mm) to stop the soil
4. Two layers of waterproof membrane.
ceiling finish.
from sliding off an angled roof. 4. Corrugated
cardboard or carpet scraps.
5. Two layers of waterproof membrane. 6. Corrugated cardboard or carpet scraps for cush
cushioning to prevent puncture of the
ioning to prevent puncture of the waterproof
waterproof membrane and to give the
membrane and to give the roots a base to wrap around.
7. Soil.
7. Soil.
8. Plants.
8. Plants.
5. Corrugated cardboard or carpet scraps.
Sonora, Mexico.
from being punctured and to give the vegetation something
2. Plywood or other rigid board.
6. Corrugated cardboard or carpet scraps for
roots a base to wrap around.
1. Rafter.
Roof construction consisting of carrizo decking with straw-clay for insulation used on houses in Xochitl,
LOW -CO ST
FLAT
ROO FS
6. Soil. 7. Plants.
Roofing is one of the biggest challenges in low-cost constructi on, since it is usually the most expensive part of the structu re. When I worked in Mexico on a housing project organized by the Canelo Project, the roof systems developed were for straw bale houses that cost between 350 and 50 0 U.S. dollars. The roof types we used
Cardboard box roof construction used on the houses in Aves del Castillo, Sonora, Mexico.
ROOFS
73
72
powdered marble, white cement and acrylic waterproofing as the roof finish
straw-clay layers of carrizo forming the roof decking 75 -1 00 mm (3 '-4') Ø vegas
earthbag wall
there are also well suited for low-cost
insulation blown in between rafters, which
proof membran e is placed between the
earthbag construction.
could be recycled cellulose, hemp, wool, or
decking and the straw. Then straw bales
For the rafters we used 3- to 4-inch- (75
coconut fiber. As for insulating a flat roof,
are laid flat, leaving a gap of 3 to 4 feet (1
to 100 -millimeter) diameter poles, dis
if pumice is locally available it can be used
meter) at the edges where flakes of straw
carded from timber cutting operations
by placing 8 to 12 inches (200 to 300 milli
can be used to taper the roof to the height
because they were too small for convenient
meters) or more of small pumice (only
of its frame. When the bales have been laid,
milling. The roof surface or decking was
small particles of pumice wick moisture)
cut all the strings to loosen the straw. For
constructed of carrizo and covered with
with 6 inches of earth on top to allow for
the first winter and spring, leave this ex posed to allow the straw t o soak up the
two layers of straw-clay mix. The first layer
planting . An insulated roof has to be
Roof construction using cardboard boxes filled with straw on a concrete-
of the mix contained uncut straw to sculpt
framed in at the edges like a box to contain
moisture, then cover it with a very thin
reinforced grid supported by chicken wire.
the parapets and build necessary thickness
the large volume of materials.
layer of aged compost and sow flower
powdered marble, white cement and acrylic waterproofing as the roof finish
reinforced concrete beams forming a lattice around the boxes
cardboard box filled with straw
(6 to 7 inches) to provide reasonable insu
Another type of insulated living flat
seeds. The best plants for such roofs have a
lation value. The second layer contained
roof uses straw bales as insulation. The
shallow root network and retain moisture
finely chopped straw and clay to even out
slope should not exceed 30 degrees. As in
well, for instance strawberries. Imagine
the surface and prevent puddles. The roof
the other living roofs discussed, a water-
having a roof full of strawberries!
finish was a mix of powdered marble, white cement, and an acrylic waterproof ing compound as a final coating (see the discussion of waterproof finishes in chap ter 6).
chicken wire
Another low-cost alternative optio n for
A durable finish for flat straw-clay roof surfaces can be made with a capping of two coats of ½-inch (12 milli meter) li me render (1 part lime to 3 parts sand).
a dry climate (used by the Canelo Project Roof construction consisting of carrizo decking with straw-clay for insulation and
in Mexico) is a roof made out of cardboard boxes filled with straw or other insulating
sculpted parapets.
material, which are laid flat on some form powdered marble, white cement and acrylic waterproofing as the roof finish
carrizo precast concrete "vigueta"
Precast concrete vigueta roof system with carrizo and straw-clay insulation. Viguetas are short structural supports that span between main beams. Instead of concrete viguetas, short timber poles could be used.
1. Dissolve 2½ ou nces (70 grams) of alum (alumi num potassium sulphate) and 2½ ounces (70 grams) of salt in 2 cups (Viz liter) of water. Add this mixture to 5-1/3 quarts (5 liters) of water and
of inexpensive joist or rafter arr angement,
mix in 1/16 sack of lime. Use this to paint over the finished lime-plastered roof surface.
or chickenwire for support, as shown at
2. Apply five coats of dissolved alum an d soap, alternating these in t he following wa y:
left.
straw-clay
Here are two recipes for waterproof finishes to be painted on the surface:
Day 1: Dissolve 14 ounc es (400 grams) of soap in 4 cups (1 liter) of hot wate r and brush on roof surface.
R OO F I N S U L A T I O N
Many materials can be used to insulate a
Day 2: Dissolve 14 ounce s (400 grams) of alum in 4 cups (1 liter) of hot water and b rush on roof surface.
roof, the lower-cost options being strawclay (a thick clay slurry mixed with a lot of
Alternate these for five days, and reapply every year or two.
straw, as shown in figures a and c on page
Recipes make enough finish for approximately 30 square meters.
70 ) or straw bales, as described below. A slightly more expensive option would be
WEA THE RPR OOF ING
A N D
F I NI S HE S
A
within the first two months of exposure to
buil der s. As the cob buil der' s prov erb of
the material inside the bag. If the material
Devon, England, says: "Good shoes, good
inside the bag has 10 percen t or higher clay
s with any building, keeping the
water out of an earthen house is
ultraviolet light (direct sunlight), as UV
one of the greatest concerns of
light makes the bags deteriorate, exposing
hat, and a coat that breathes." This is what
content and the structure was properly
an earthen house needs to survive for
tamped or rammed throughout the con
many decades.
struction process, the walls should remain
Good shoes, to raise the building suffi
solid and stable even when the bags have
ciently off the ground—a sturdy, well-
deteriorated. However, if the fill is of a
drained foundation.
loose composition, such as silt, sand, grav
Good hat, a generous overhang to pro
el, or pumice, the bags must be covered.
tect the walls from erosion from the rain.
The type of covering used will depend
A coat that breathes, a plaster that allows
mainly on the climate and on the design of
the passage of moisture. This chapter applies to internal and ex
the house. For example, a dome in a rainy climate will require a plaster that is water
ternal earthen plasters (often called "ren
resistant, such as lime, papercrete, or ce
ders," when exterior) for earthbag domes
ment-stabilized soil. In extremely wet cli
and other types of earthbag houses, as well
mates a waterproofing layer on the top
as compatible finishes for benches, ovens,
par t of a do me o r vau lt is e ssentia l (see the
stoves, or any other earthen structures.
chart on page 7 7 ) . If the water-resistent
Facing page:The Hart's
In the earthbag construction system,
render becomes saturated with water and
dome covered with
the wall surface is never the bare earth, but
has no form of sealant or impermeable
papercrete render.
whatever material the bags are made out
membrane, the moisture will go down with
of. Rendering an earthbag house is neces
gravity through the earthbags. If the inte
sary for several reasons.
rior is covered with an earthen plaster, this
If the bags used for the construction are
will quickly absorb water and come apart.
poly prop ylen e, they need to be covere d
On the other hand, if the house is designed
WEATHERPROOFING
76
with a conventional roof and wide over
(water-thirsty) properties, and then re
hang, and is raised up from the ground by
leased to the outside. There may be no
the foundati on and stem wall. The walls do
other building material capable of regulat
not need a water-resistant render, being
ing moisture levels as effectively as clay,
prot ected from the drivi ng rain, and an
which continually absorbs and releases
earthern render can be used externally.
moisture in response to the humidity of
If the bags used are made out of burlap
the home. With thick and solid rammed
(hessian), they will also need to be covered,
earth, adobe, or cob, an external render
but they have a l onger exposu re life t han
FINISHES
77
may not be necessary. In Devon, traditional cob houses have
polyp ropy lene. Another reason for rendering the exte
AND
survived for centuries without any plaster
rior of a wall constructed out of earthbags
coating (they say it takes one hundred
is that the surface has many grooves and
years to wear away one inch of cob). Pro
seams that in some extreme weather con
vided that cob walls are protected from
Finishes for earthbag
Meanwhile, among the disadvantages
domes and walls.
ditions can be penetrated by rain, which
actual erosion caused by the abrasion of
must be prevented of course. The grooves
driving rain, there is no necessity for exter
of earthen plasters are that they have a low
The purpose of the first layer is to fill in
can be extremely useful when applying a
nal render, because moisture will evapo
structural resilience, therefore the design
large gaps and crevices and to build up the
render, however, providing a "key-in" area
rate very quickly from an exposed cob sur
of the house is critical. If they are made
main bulk, creating a fairly even surface
for both external and internal plasters. If
face. With earthbag construction, how
with earth that possesses a high clay con
for the smoother plaster to go on. This
for aesthetic reasons the ribbed pattern on
ever, rendering the external surface is a
tent, or with very fine sand or silt as the
first layer contains straw that is either un
the wall is desired, a render can be sprayed
necessity, as emphasized above.
filler and little or no straw, the plaster may
cut; direct from the bale, which provides
They can be applied in two or mo re stages.
be easily er oded. Als o, ear then plaster s are
an interwoven stability; or finely chopped,
For earthbag
ishes are these attributes:
affected by frost in cold climates; if mois
which is easier to mix in larger quantities
houses with
ture is allowed to penetrate the surface, it
and is also great for building up thickness.
conventional
• moisture-control
will expand and contract as it freezes and
Long straw in the mix creates a plaster-
that contains clay, the plaster should be a
• fire-resistance
thaws, breaking up the plaster. In cold ar
reinforcing network and helps to fill out
coating that breathes, allowing any mois
• odor-absorbent
eas it is a good idea to cap the earthen plas
large holes or build up bulk where it is
ture that enters the wall to escape. Earthen
•
ter with a lime plaster.
needed, as in sculpting the sills around
plasters have been used extensively in
• when dry, are unaffected by frost
on, retaining the pattern of the bags. EART HEN
Among the advantages of earthen fin
PLASTERS
If any plaster is used on a bare ea rthen wall
many countries for many centuries. As
nontoxic
In locations where the plaster finish is
• aesthetically pleasing
well as being used as a finish coat for
windows.
steadily eroded by weathering, it has to be
An earthbag wall contains indentations
maintained on an annual basis. This can
between the co urses of tampe d bags, mak
be t urn ed into a fun ritu al.
ing it easier for the plaster to "key into,"
adobe, cob, or s traw bale they also make an
Earthen walls covered with earthen
excellent covering for earthbag walls that
plaster may give the impr essi on o f havin g
have a roof overhang. With earthen plas
grown out of the landscape. Their subtle
ters, whatever moisture does penetrate
colors,
the
Earthen plasters are incredibly flexible to
earthen plaster being keyed into the wall.
into the walls will be absorbed automati
ground that surrounds them, can add
work with, allowing everyone to find a
A good plaster mix is already well rein
cally by the clay, due to its hygroscopic
greatly to the charm of the countryside.
pers onal way of mixin g and plaste ring.
forced by straw. As this first coat of plaster
complementing
those
of
or adhere. No plaster-reinforcing lath is A P P L I C A T I O N
necessary, as this can interfere with the
roofs providing appropriate overhangs, no waterproof layer is needed.
WEATHERPROOFING
78
AND
FINISHES
79
is applied, it should not be smoothed out
As explained below, if an earthen plas
with fibers, or adding lime, bitumen, or
be reused (see the diag ram on page 81
too much, but instead left rough, or into
ter is well mixed and contains a good dis
cement." (Houben & Guilland 1 9 9 4 ) When
showing the lime life cycle).
finger-sized holes so t hat the next layer of
tribution of clay, aggregate, and straw,
choosing the best stabilizer for a particular
In industrialized societies, an increas
earthen or lime plaster will adhere. If the
adding stabilizers can be largely avoided
soil, many factors such as the clay content,
ing number of people have been affected
plaster does not stick to the wall, pou nd
through design features. But earthen walls
acidity, and texture must be taken into ac
by "sick buil ding syndr ome," which is a
wooden pegs into the grooves between
and plasters must be stabilized if the
count, and many samples- must be made
form of poisoning harming people who
courses; these can also be inserted during
earthen mix does not produce enough
pri or
live and work in buildings with insuffi
construction.
bind ing stren gth (that is, doe s no t con tain
CRATerre, "It is particularly unfortunate
cient ventilation in which toxic vapors are
enough clay). Yet remember, houses built
that many practitioners of systematic sta
given off by artificial, chemical-intensive
more refined and can be very thin, just
out of earth need to move slightly over
biliza tion do n ot kno w, or do n ot ap preci
build ing mater ials and pain t. Cemen ti-
enough to allow a final smoothing out.
time, and they are especially sensitive to
ate the original characteristics of a soil, and
tious finishes release carbon dioxide, a
This can be a mixture of finely sieved sand
dampness and temperature, so they need
start about stabilizing soil with undue
greenhouse gas, as they cure. Over the
and clay and, if desired, finely chopped
to breathe, releasing moisture. Modern
haste, when it is not particularly useful."
longer term, they seal in moisture and
straw, along with wheat flour paste or an
stabilizers and sealants result in severe
The wrong stabilization may do more
therefore can cause air-quality problems
other stabilizer.
damage to earthen buildings , because they
harm than good.
and propagation of mold.
The second coat of earthen plaster is
STAB ILIZA TION
AND
to
cons truc tion .
Again
from
tend to restrict movement and permeabil
As a case in point, cement can be a real
Cement is also a more expensive mate
ity to moisture. Lime-based or other natu
enemy of earth architecture, apart from
rial, because it contains higher levels of
ral stabilizers do allow the walls to breathe
the few selected applications such as bond
embodied energy, although unfortunately
Stabilizers are generally used to make ren
and move, adhere much better to earthen
beams on t op of walls, compre ssio n rings
in some countries where demand for lime
ders or plasters more durable and resistant
walls (not requi ring chicken wire or stucco
in domes, and stabilization of sandy soil
is very low (as in the United States), the
to moistur e. They are the "glue" that can be
netting), and produce more porous fin
when making soil cement, which can be
healthier optio n can be as expensive as ce ment. The benefit of lime is its superior
A L T E R N A T I V E S
used to bind filler particles such as sand,
ishes than Portland cement, the most
applied as a render to earthbag domes in
earth, gravel, or fibers such as straw. Stabi
widely used industrial stabilizer, which is
areas with high rainfall. But cement should
quality, and when properly applied it is
lizers can be used as additives to earthen
an expensive and environmentally contro
never be applied on top of an earthen plas
worth every additional effort and expense.
plaster s if th e e arth mix does not contai n
versial material, as discussed below.
ter, as this will eventually crack and peel
enough clay to provide the binding force
It is possible to improve the characteris
Sources of stabilization include:
off. As a general rule in earth architecture,
tics of many types of soil (especially sandy
never place a hard, modern, nonbreathing
• ve getable stabilizers
Stabilizing earth is a very complex pro
soils) by adding stabilizers. These stabiliz
material on top of a more flexible surface,
• processed natural binders
and moisture resistance required. cess, since not all stabilizers are effective
ers can be used in the earthwalls them
as this will never form a solid bond and will
• animal stabilizers
with all soil types, and t here are many fac
selves or in their skin as a surface protec
eventually separate, as well as create con
• mineral stabilizers
tors that influence compatibility, includ
tion. Due to the vast variety of soil types,
densation and other moisture problems.
ing clay content, soil particle size and type,
stabilization is not an exact science, and
Buildings constructed of local stone,
If a house is built in rainy or damp cli
pH balance , and climate . Othe r factors
research is contin uous. According to CRA-
earth, and lime cause far less environmen
mates, the walls could be prone to severe
that must be taken into consideration are
Terre's Earth
Construction, "The best
tal damage than concrete and steel. Earth
weathering from driving rain and frost.
the type of application and the reliability
known and the most practical stabilization
and stone are reusable, and old, dry lime
With effective planning and the right de
of periodic maintenance, as well as aes
methods are increasing the density of the
render is chemically limestone again, just
tailing, originating all the way back in the
thetics and cost.
soil by compaction, reinforcing the soil
as when it was first quarried and can also
initial design and building process, it may
WEATHERPROOFING
8o
AND
FINISHES
be possib le to forgo the use of s tabilizers
inches away from the wall to allow for ven
the whole ques tion quite satisfactorily. satisfactorily. As the CRATerre CRATerre publica
and instead use a plaster made of just
tilation.
tion Earth Construction explains,
earth.
Adobe walls are traditionally protected there is clearly a tendency at present to the over systematic
There are several ways to protect
by eart hen plaster s that are annual ly
earthen walls without using lime or Port
"topped up," but allow the wall to breathe.
use of stabilization, which is regarded as a universal panacea
land cement for stabilization. During the
This can also be applied to earthbag as well
for all problems. This attitude is unfortunate, as stabilization
design and detailing process, familiarize
as straw bale houses. Other ways of mini
yourself with the direction of the sun and
mizing the penetration of moisture in
can involve considerable extra costs, ranging from 30 to 50 percent of the final cost of the ma terial. Furt hermo re,
driving rain, and plan accordingly to pro
clude sealing the earthen plaster with oil or
stabilization stabilization complicates the production of the material. It is
vide a roof with a large overhang (a mini
whitewash (see list of sealants starting on
thus advisable to insist that stabilization is only used when
mum of 18 18 inches or 4 4 50 millimeters on the
page 9 2 ) ; stabilizing the earthen plaster
absolutely essential and that it should be avoided where
least problematic side). Extra-large porches
with lime, wheat-flour paste, or other
economic resources are limited.
can be integrated into the house layout on
plant , anima l, or mine ral stabilizer s (see
the sides that are most vulnerable from
the list starting on page 8 1 ) ; or putting a
wind-driven rain. The more protected the
final cap of lime—a more durable, bu t still
walls are, the less protection that plaster
breat hing s urface, over t he ear then plaster.
needs to provide. Remember, each wall can
Prior to any constr uction, it is crucial to
be slightl y different; t he mos t expos ed wall
7 for a discus know your soil. See chapter 7
can be the only one capped with lime plas
sion of soil-testing methods.
ter. Always slope surfaces away from the
Stabilization is not compulsory. If the
ground around the base of the house as
soil contains enough clay, you can ignore
well as sculpted windowsills, alcoves, or
Vegetable Stabilizers
The following vegetable-based materials will serve as effective sta bilizers for ea rthe n p laster s: • oils—coconut, linseed, and cotton, which need to be in "boiled" form to speed up the drying process • juice of banana leaves, precipitated with lime, improves erosion resistance and slows water absorption
seating to shed the water. Design these to
States)
the wall, with a drip edge (see the diagrams
• wheat flour paste, or any starchy material Stabilizers function as binders in the
installed as necessary to stop the seasonal
mixture but are not sufficient on their own.
Linseed oil can either be brushed on the finished surface of an
rain, or to prevent melting snow from
To make them solid and hard, they need to
earth plaster, as is often done wi th the final layers of earthen floors
eroding the walls, for example a bamboo
be com bined w ith othe r fillers, fillers, for example
7) or can be mixed into the final batch of plaster itself. (see chapter 7)
or willow screen. Or if bad weather is year-
nonexpansive particles of soil such as sand,
round, on the side where the most snow
silt, gravel, or fibers.
settles or the strongest winds blow, a high stone wall could be incorporated into the base of t he walls. P erma nent screens co uld also be built to keep driving rain off the wall, keeping a distance of a couple of
Harvesting prickly pear cactus.
• prickly pear juice (found in the southwestern United
extend out at least 2 inches ( 50 mm) from on page 6 1 ) . Temporary screens could be
81
Never layer a rigid, modern, nonbreathin g material on to p of a softer, breathin g surface. The layers will eventually separate.
To make prickly pear juice, the cactus has to be boiled unt il very soft, soft, then its juices squeezed out. The resulting soupy liquid is then combined with the clay and soil mix that is to be used for the plas ter finish. Like any other stabilizer, this has to be tested prior to use, as it reacts differently with different soils. Wheat flour paste is an inexpensive stabilizer for earthen plas ters that is used by natural builders throughout the United States.
Prickly pear cactus being boiled.
WEATHERPROOFING AND FINISHES
82
83
I learned it from Carol Crews of Gourmet
To make casein glue to stabilize earthen
Adobe, while we were making clay paints, and it can be applied like a paint to earthen
plasters, soak about 1 ounce (25 grams) of casein powder and ¼ ounce (8 grams) of
plaster s or floors. It can be made using
bora x in enou gh wat er to form a put ty (to
commonly available flour, as described on
make casein, see page 98). The putty can
page 96.
samples before beginning to plaster an en tire wall. LIME
PLASTERS
Historically most buildings in the United
then be diluted with water to a consistency
Kingdom used lime for interior plasters
To make a plaster without using lime or
suitable for mixing with the soil ingredi
and exterior renders. Cob buildings, if
clay as the binder, you can combine sand
ents of the plaster. For mor e casein recipes
rendered at all, were traditionally covered
with manure and wheat flour in the fol
see the end of this chapter.
with a lime-based render applied directly to the cob. This render consisted of lime,
lowing proportions: An earthen house with partial lime render, Peru.
Mineral Stabilizers: Lime
4 parts flour paste (see page 96)
For thousands of years in Europe, lime has
3 parts sand
been used as a mor tar for stone or brick
2 parts manure
construction; as an exterior or interior
which serves as the binder, and sands an d/ or aggregates, which provide bulk at low cost, and which control shrinkage. It is
ter or adobe mix that contains clay, be
best to use aggre gate tha t has a good r ange of particle sizes.
plaster, when mixed wit h s and; and w hen
cause the lime and clay seem seem to "compete"
Other processed natural binders that
mixed with water, as a white paint com
as binders. Ideally the mixture should tur n
Fiber—for instance, hair—was often
can be used to stabilize earthen plasters
monly known as whitewash. In the mid-
into a creamy paste, which will result when
added to the traditional mix to minimize
when too little clay is present include
nineteenth century, cement and gypsum
it is dry in a finish that is more wear- and
the shrinkage cracks that often occurred.
wallaba resin; rosin from oily pine resins,
unfortunately
common
water-resistant than clay alone, alone, but in real
Cow hair was preferred, but was harder to
obtained during distillation of turpentine;
buil ding mater ials. Lime was slower to
ity this is rarely achieved due to variations
obtain, so goat hair was frequently used.
copal, made from tropical tree resins,
build with , and requ ired artis inal skills
in the pH of clays. Therefore combining
Some straw bale houses that are being ren
3 to 8 percent for added in a proportion of 3
and good climatic conditions during ap
clay and lime can make a crumbly mix, and
dered in lime use straw as the fibers.
sandy soils; gum arabic, from the acacia
plica tion, but prod uced dura ble and at
when used for stabilizing a wall material
Using lime plasters has several advan
tree; and molasses.
tractive results. Lime plasters and finishes
such as adobe, can reduce its compressive
tages. When lime used in buildings has set,
harmonized with seasonal changes in hu
strength.
it turns back to limestone, which is chemi
became
more
Animal Products as Stabilizers
midity and temperature, like clay prevent
The theory is that, since lime is alkaline,
Among the most popular animal stabilizers
ing an overly dry or wet atmosphere by
it combines best with acidic soils. The
in use today are the following: following: eggs, blood,
evaporating away excess moisture or ab
higher the pH of the soil, the m ore lime is
and casein (dried milk) as proteins; urine
sorbing it as necessary, fostering a healthy
needed to stabilize it. Lime apparently
reacts with carbondioxide
and manure, as uric acid; casein (dried
living environment. Simultaneously, due
does not react well with alkaline soils,
CO
to its alkalinity, lime does not allow the
therefore carrying out tests is crucial to
growth of mold on the walls, therefore cre
finding out the soil's behavior. If the mix
milk); and glue made from animal parts or bypr oduc ts. Termites secrete a chemi cally
ating healthier conditions in wet climates.
of earthen plaster and lime does not turn
up well to rain. Their soil can be mixed
Using lime as the binder in renders,
smooth and creamy, the addition of either
with other soils for the production of
plaste rs, and mor tar s works best when
a more acidic ingredient such as manure
blocks that adhere effectively; perhap s this
sand is the filler. Lime is no t the most effec
or organic soil may help. But care needs to
soil would also stabilize earthen plasters.
tive stabilizer to use with an earthen plas-
be tak en; always test the mixes by mak ing
active substance, and termite hills stand
cally the same as the lime that is quarried,
limestone
2
heat causes carbon dioxide to escape
HO 2
when drying water
The life cycle of lime.
evaporates lime putty
quicklime
After Lime in Building by Jane Schofield (Fig.
HO 2
water is added
108, p. 123)
WEATHERPROOFING AND FINISHES
84
since the water has been driven off, it be
tool for large quantities). As more quick
for a long time, which means many of the
comes very "thirsty" and reacts dramati
lime is added, the mixture starts to boil
parti cles in the mix will have already re
cally with water (even water in the air, or in
and bubble. When that happens, stop add
acted with moisture in the air and carbon
the skin or eyes).
ing quicklime and keep stirring until the
dioxide to form limestone, making them
When the quicklime is soaked in water,
mixture ceases bubbling, or else the lime
inactive and therefore weakening the mix.
it turns to slaked lime, due to hydration.
will burn and be of lower quality. quality. The bet
To make lime putty out of bagged hy-
This process produces a lot of heat, as the
ter the quicklime mix, the faster the hydra
drated lime, mix the lime with water in a
mixture boils violently. This is known as
tion process occurs. The mixture should
bucke t to form a past e, cover this mixt ure
slaking. The resulting slurry is calcium
be st irred cont inuo usly u ntil all the l umps
with more water, and put an airtight lid on
are broken down, and until the mixture
the storage container. Store for several
has cooled down and is of a creamy consis
weeks before using. Make sure it does not
hydroxide
(Ca(OH) ), known as lime 2
putt y. When applied on a wall surface and
tency. It can then be sieved through a 7 1 6 -
dry out by adding water to it occasionally. occasionally.
therefore exposed to air, the lime reacts
inch (2 mm) sieve to take out the un-
The longer it sits the better it gets. If this
with the carbon dioxide in the air to form
Slaking lime in Xochitl, Mexico.
quality, mix 1 part of the resulting putty
therefore it can be reused if the building is
ate, (CaCO ). This happens as it dries on
When left standing, the lime sinks and the
with 2½ parts sand (instead of the 3 parts
destroyed and does not involve any pro
the building. The water evaporates, and
water sits on top. For best results it is rec
suggested below) to compensate for the
cessing that will harm the environment.
the lime hardens through carbonization,
ommended to leave it to mature for at
inactive particles. To further strengthen
thus completing the cycle (Schofield 1 9 9 4 ) .
least three months prior to any use to en
bagged hydra ted lime, add some of the
3
sure that all the calcium oxide has hy-
more expensive "hydraulic" lime, which
Making Lime Putty (Slaking)
drated, and the longer it sits the better it
sets faster and is more frost resistant after
atmosphere, because the moisture is ab
For this task it is necessary to wear protec
will be, though in Mexico we used it after
sorbed and then given out, contributing to
tive clothing, including gloves, goggles,
only one month. While curing it must re
higher air quality. Also, due to its alkaline
and mask. Since quicklime is caustic, it can
main in a sealed container to prevent it
prop erti es, lime preven ts m old prob lems .
bur n your skin, and dur ing the slaking
from drying out, which is the carboniza
Lime is ideal for use both as an exterior
process the mixt ure can spit violent ly
tion process whereby the lime putty will
while boiling.
turn back to limestone, losing its binding
ations, lime plasters and washes usually
quicklime to
bagged l ime i s no t very fresh or of th e best
The resulting mixture is lime putty.
preve nt conde nsat ion and an overly dry
water, never add
bur ned limes tone pieces.
limestone again, that is, calcium carbon
In terms of healthy-home consider
Always add the
85
render or as an interior plaster or wash. The chemical process of obtaini ng lime
water to quick
involves
heating
calcium
carbonate
It is recommended to use 2 parts water to 1 part quicklime.
prop erti es a nd the refore becom ing us eless as a plaster.
lime, as this can
(CaCO
from limestone or shells shells to 1,200°
Slaking has to be done outdoors with a
Lime putty made from quicklime is by
cause an
Celsius. This can be done in kilns (shells
metal container, making sure it is not
far a superior material to the bagged hy-
explosion!
can also be heated in a pile covered with
placed on any flammab le mater ial, be
drated lime available from garden supply
cowpats and coconut husks). The heating
cause the container will get extremely hot.
stores, which when soaked in water pro
causes carbon dioxide (CO ) and steam
The water is poured in, then quicklime is
duces a putty that is generally not as good.
(H O) to escape, and quicklime, or cal
added slowly to the water, with one person
The problem with the bagged material is
cium oxide (CaO), remains. At this stage,
stirring at all times (a backhoe is the best
that it might have been sitting in the shop
3
2
2
Earth houses with lime render on a street in Cuzco, Peru.
WEATHERPROOF ING
86
AND FINISHES
87
parti cular ly reco mmen ded, because then
When preparing the plaster, it is important
good compromise is 1/3 hydraulic lime to 2/3
the filler binds especially well. If sea-
to mix and beat the lime putty for a long
marks and spray the first coat with lime-
hydrated lime.
dredged sands are used, they require wash
time on a wo oden or plywood surface with
water before re-coating. When the second
ing several times in clean water to remove
wooden mallets and posts to get it to be
coat is hardening, it may be worked over
salts.
come more plastic, and then work it well
again to improve the finish, remove any
into the sand. The more you mix, the bet
rough spots, and push closed any small
just thre e days instea d of two weeks. A
Making Lime Plaster or Render
In order for a lime plaster to dry and be come limestone again, it needs to give off
The most popular proportions of lime put ty to sand is:
ter the plaster.
Knock off any lumps around the score
cracks. More detailed instructions can be found in the book Lime in Building: A
all its moisture and draw in carbon diox Application
Practical Guide by Jane Schofield (see the
layers. When applying a first coat of l ime to
Make sure there is good adhesi on between
bibli ograp hy).
an earthbag surface, much crushed aggre
the lime and the earthen plaster under
Protect the plastered surface from sun,
gate or straw needs to be added to allow for
neath. (Remember, before the earthen
wind, and frost to prevent it from cracking
ide; therefore, it cannot be applied in thi ck
drying in the deepest areas keyed in be tween the bags. It is therefore better to first
1 part lime putty to 3 part s sand
• The durability of lime depends upon the. quality of lime and the right mix, as well
cover an earthbag wall or dome with
as the quality of the application and the
earthen plaster to fill in those deepest
drying conditions. Variables in the mix of
voids before applying subsequent coats. Lime plasters can vary enormously, de pend ing on the type of lime, aggregate, and particular use. The proportions of lime to sand may vary between 1: 2 for a smooth, fine finish to 1:5 for a rough first coat. For greater strength in a plaster, the sand particles used should be well graded, ranging from very fine to coarse in one mix. As mentioned earlier, the only differ ence between the mix for interiors and ex
ditionally lime-sand plasters have been
days with virtually no wind and a slight drizzle. One way to provide protection
millimeters thickness each. When apply
from the sun is to hang wet cloths a few
and the particle sizes—are crucial, as are
ing lime plaster, the earthen plaster (or the
centimeters away from the plastered sur
the weather conditions during the
earth wall) undern eath must be fully dried
face. Frost can also be very damaging dur
application process.
out then slightly dampened to help the
ing the drying period, and frost protection
• Apply in thin layers and make sure the plaster is well keyed into the layer below. • If using lime to stabilize soil, always test your mixture in advance. If not enough lime is added, the compressive strength can be lower than that of unstabilized earth. • Do not overwork lime plaster with a metal trowel. This makes lime come to the surface and can form a hard crust over a softer backing, weakening the
and a coarser for the outside—from very
plaster.
fine dust to as large as 3/16 inch (5 millime
• Before application, make sure you cover
ters) for interior plaster, and up to twice as
all metal surfaces, as the lime can stain.
tion of moisture. Limestone aggregate is
slowly. Ideal conditions are h umid, cloudy
lime and sand—including proportions
gregate. A finer mix is best for the inside,
angular in texture to reduce the penetra
during the drying process. It needs to dry
make finger-sized holes for "keying.") Tra applied in two coats of not more than 10
teriors is the size of the sand or other ag
large for exterior renders, which should be
plaste r dries , to scrat ch its surface and
• Do not put lime plaster on top of gypsum, wood, or latex.
lime grip the earthen surface. It is best to
may be needed for a minimum of two
use limewater for this ( made by dissolving
weeks after the lime has been applied.
2 to 3 percent of lime in the water). After application of the first coat it
Pozzolanic Additives to Lime Plaster
should be scored to provide key-in areas
Pozzolanic material can be added, ground
for the second coat. This can also regulate
up into a powder, to speed the setting of
the shrinkage cracks. Noticeable shrinkage
lime and to help the lime mix set deep in
in the first coat can serve as a warni ng that
side the wall, which is necessary when us
either the lime is too fresh, the mix is too
ing lime as a mortar in stone or brick con
wet, or the plaster is applied too thick; the
struction, or as a render directly on top of
second coat should be thinner, as a safe
earthbag walls where there are deep inden
guard.
tations. Some examples of pozzolanic ma
The second coat should be applied
terials are crushed clay bricks, clay tiles,
when the first is "green-hard"—th at is, too
shales, potash, and pumice. Pumice is a
hard to dent when pressed with a knuckle,
naturally occurring pozzolan from volca
but soft enou gh to mar k with a t humb nai l.
nic areas. These pozzolanic materials
89
WEATHERPROOFING AND FINISHES
—from the Earth Building Association, Devon, England
(can be applied as a first coat to earthbag walls) 12 parts coarse sand
speed up the setting of lime due to th e re
phal t are b itu min ous . The use of bi tum en
active silica present in them, which com
as a stabilizer is very ancient, dating back at
bine wi th lime at o rdin ary temp erat ures i n
least to Babylon in the fifth century B . C . E . ,
the presence of water to form stable, in
where it was used for making mortar or
STABILIZATION
soluble compounds with cementing prop
laying unbaked molded bricks. Bitumen
Cement should o nly be used as a stabilizer
erties. The rate of reaction is increased by
mixed with soil acts as a water-repellent,
in plasters as a last resort in cases where the
increasing the fineness of the pozzolanic
reducing penetration and surface erosion
soil does not contain enough clay and
material (Spence & Cook 1983).
from wetting, therefore serving more as a
other, more nat ural stabilizers aren't avail
3 parts lime putty gaug ed with 1 part pozzolanic additive (for example, brick dust)
clay with pure linseed oil and applying it onto earthen plasters.
STABI LIZAT ION
FOR
WITH
CEM ENT
waterproofing element than a binder. It is
able. For instance, if lime is no t available,
most successfully successfully used with granular soil,
soil stabilized with cement can be used on polypr opylen e earth bags contai ning sandy
W A T E R P R O O F I N G
in which it improves durability, but is also
2 parts coarse sand
In additi on to the water-resistant layers on
widely used with clay soils, for instance in
fill with little or no clay. Cement interferes
1 part grit (up to 4 millimeter diamet er)
domes, extra protection is needed in ex
the manufacture of adobe bricks. Stabili
with the bindin g forces of clay; clay; therefore,
1 part lime putty
tremely wet climates. Imperviousness will
zation with bitumen is in fact most effec
care needs to be taken when deciding on
help to reduce water erosion, swelling, and
tive in a process involving compression, as
the quant ity of cement to be added to your soil; the higher the clay content, the more
1 bucket mix to ½ buc ket of teased hair. Omit hair in the final thrown coat. Hair must be teased out with carding combs to
shrinking when the plaster material is sub
in production of compressed clay blocks.
ject to successive wett ing and dryi ng
3 percent To stabilize adobe, 2 adobe, 2 to to 3 percent of bitu
3 cement is needed. Somewhere between between 3
cycles. cycles. For waterproofing an eart hen plas
men can be sufficient, and sometimes as
and 10 and 10 percent will probably be appropri
1 par t coarse sand
ter, a material that is unaffected by the
high as 8 as 8 percent is required. If used as a
ate, but tests should be carried out to de
1 part grit (up to 4 millimeter diameter )
water that fills fills the voids, pores, and cracks
stabilizer, bitumen either must be mixed
termine the necessary quantity more pre
is required.
remove the large clumps.
1 p art fine sand 1 part lime putty 1 bucket of mix to ½ a bucket of teased hair
1 part lime 4 parts wet cow dung (a few days old) 1 p art sandy earth
with solvents or dispersed in water as an
cisely (see chapter 7 for more informa
Bentonite clay is a material that is dis
emulsion. If used with soils containing
tion).
persed in the soil and that expan ds upo n
high proportions of clay, a larger amount
If cement is used, commercially avail
the slightest contact with water and pre
is required due to greater resistance to
able Portland cement has the least embod
vents the infiltration of pores. This has re
mixing. To obtain an even distribution,
ied energy (that is, it requires the least en
cently been tried as a waterproofing layer
large quantities of water need to be used.
ergy for processing and preparation). It is
in living roof construction (see chapter 5),
Solvents that can be used i nclude diesel oil,
made of burned lime and highly reactive
but i ts use is still at an exper iment al stage.
kerosene, naphtha, and paraffin (a mix
silica. It introduces a three-dimensional
4 parts lime
When used as a waterproofing layer, it
ture of 4 to 5 parts bitumen to 1 to 1 part part paraf
matrix into the soil and results in a filling
1 part fat-free quark (to make quark, see the recipe on pa ge 99)
needs to be weighed down with a large
fin oil).
10 parts sandy earth Tallow, an animal fat, increases water resistance and adhesion. Ten percent by weight of melted tallow can be added to lime; this can also be replaced by linseed oil.
amount of soil, as it expands and moves with absorption of moisture.
Bitumen is a mixture of hydrocarbons and other materials, either occurring
Note t hat t hese sol vents c anno t be used in the rain and are flammable. Also, bitu men stabilization is not effective in acid, organic, or salty soils.
of the voids with an insoluble binder, which coats the grains and holds them in an inert mass. While a cement-stabilized render can in some cases be used over earthbags, for in
naturally or obtained by distillation of
A simpler, more natural weatherproof-
stance soil cement or conventional stucco
coal or petroleum. For instance, tar and as-
ing solution can also be made by mixing
finishes, never use cement plaster on top of
WEATHERPROOFING
90
render or earthen plaster acts more like blot ting paper, absor bing and releasing
coat of earthen plaster or whitewash once
As emphasized repeatedly in this chap
moisture relatively freely. In addition ac
a year, the buildings have to be carefully
ter, when cement plaster is applied on top
cording to the Devon Earth Builders, small
and expensively repaired.
of earth, it forms a brittle, rigid surface
cracks may be closed by redeposition of
that is impervious to moisture. The effec
soluble material from the lime or clay.
tiveness of cement-based plaster is depen
Carol Crews of New Mexico's Mexico's Gour met
dent upon the rigidity of the wall beneath
Adobe explains the large lesson learned at
it, since the cementitious finish itself
the famous St. Francis de Assisi Church in
forms a rigid, relatively brittle shell. An
Ranchos de Taos:
the wall material. A P P L I C A T I O N
OF
STABILIZED
RENDERS
With the addition of some stabilizers the When it was coated with cement
render applied to the domed or vaulted
seismically active areas. Due to the differ
stucco in 1 9 6 7 this plaster cracked
part s of the str uctu re become s mor e
ent properties of cement and earth, tem
and allowed the moisture to pen
brit tle, and cracks can occur thr oug h ex
pera ture changes and mois tur e cycling
etrate deeply into the adobes, but
pans ion and cont ract ion with extrem e
tend to produce cracking in the cement
the relatively impermeable stucco
temperature changes, as discussed above.
render. These hairline cracks could be al
prevente d the adobes from dr ying
This movement can be controlled through
most invisible, but once the waterproof
out again. Large sections of the
the fragmentation of the render mass. By
finish is compromised, any moisture
buttre ss ha d to be rebuilt, so th e
placin g the re nder in smal l "patties ," a tex
drawn in th rough these tiny cracks will be
community has now gone back to
tured finish can provide thermal variation
trapped, unable to evaporate, and will
the annual renewal of the mud
throughout the whole surface of the struc
start wearing away at the softer material
plaster, whic h not only keeps t he
ture, creating air movement due to the
behi nd. Given enou gh time , big cavities
church building in beautiful condi
temperature differential between the sun
can be worn away, even across the whole
tion, but strengthens neighborhood
zone and shade zone within the render it
width of a wall. This would not be such a
ties as well. (Kennedy 1 9 9 9 , 9 5 ) It is surprising that even after experi ences of this kind, the U.S. Unifor m Build
monastery in Abiquiu,
not wear very noticeably, therefore hidin g
ing Code continues to stipulate the use of
Santa Fe, New Mexico.
the problem until entire chunks of wall cave in or collapse.
self, never allowing the surface to overheat. As one side of a rounded patty heats up,
surface of the cement-based plaster does
adobe wall of the
As a general rule: Renders should have a
permeability equal to or higher than that of
this is normal, and is even beneficial in
enough, as the wear is very gradual. But the
91
allowed to simply give each house a thin
adobe or cob walls or a nonstabilized
prob lem if the dam age were detecte d early plaster cracking off an
FINISHES
earthen plaster!
earthen wall continues to move over time;
Chunks of cement
AND
cement plasters on top of the adobe walls
the other cools down. This surface has been used for c enturi es in African villages and is prevalent in nature, for example in the scales of a fish or the tru nks of trees.
in several of the Pueblo Indian villages in Application
Such moisture damage is most likely to
New Mexico. With cemen t-bas ed r ender s,
occur where hard, modern materials are
a great deal of work is still required for
Once you have chosen the right stabilized
applied as a finish to a building whose un
maintenance, but often the result is a
mix (clay, lime, cement, etc.), apply a
derlying structure is made of softer, more
patchy surface, since repairs with cement
"scratch" coat to fill in large cavities and
flexible earthen materials. A lime-based
plaster s are usually visible . Instead of bei ng
create the desired overall shape. Leave any
Top: The textured, stabilized render applied to the waterproof layer (roofing felt) on a vault in California. Inset: Textured surface of a vault. Bottom: Fragmented "patties" of cement-stabilized soil placed directly on the surface of the earthbag dome, California.
WEATHERPROOFING AND FINISHES
irregularities in the surface so the second
can be combined with perlite for a more
There are two types of sealants: those
coat has somewhere to key into. To
lightweight, better-insulating mix. Pig
that form a skin or a shell, and those that
achieve the bubbly effect, effect, patties of stabi
ment can be added for a more colorful
penet rate deeply into the earth . Sealants
lized soil are placed like roof tiles, overlap
outcome. Gypsum can also be mixed with
that form a skin or a shell are fine, as long
ping each other, start ing at the base (like
lime putt y to create a faster-setting plaster
as they breathe (lime is an example of one
laying tiles) tiles) and working up the s tructure.
than lime alone.
that does). The main pro blem with "skins"
Stagger the cracks so water will run down the grooves (see the photo on page 91).
As an alternative to two coats of con
is that they create a thin hard cap on top of
ventional plaster for walls and ceilings,
a relatively soft surface, which can be easily
clay mixed with sand and fiber may be
damaged under pressure. On surfaces
more appealing. (See chapter 7 for more
where pressure is constantly being ap
There are many ways of finishing the in-
on mixing clay plasters.) Clays come in
plied— as on an eart hen floor —the right
sides of earthbag walls, but whichever
many different colors, and beautifully col
choice of sealant would be one that pen
Interior of a cassita in
method is used for the final coating, it is
ored finishes can be achieved using only
etrates deeply into the earth rather than
Canelo, Arizona. The
best to coat the uneven earth bag surface
the earthy clay colors, for there is s eldom a
forming a shell-like surface. This is why,
with an earthen plaster to fill in any large
prob lem with the colors clashing . Mica
when sealing an earthen floor with linseed
white bench is
cavities before the other layers are applied.
can also be added to a final coat of clay
oil, it helps to heat the oil to make it soak in
plastered with gypsum.
As discussed above, lime mixed with
pain t or plas ter, whic h will add a glitt ering
as deeply as possible. To encourage the oil
texture.
to penetrate even deeper into the floor, it
INTERIOR
FINISHE S
very fine sand is a great material to use on
walls have a clay finish with mica for shine. The
top of interior earthen plasters. Another is
Earthen plasters are usually applied
can be thinned with various thinners (see
gypsum. Gypsum is a naturally occurring
with hands or a wooden trowel, but for
7) . Good seal "Earthen Floors" in chapter 7)
soft rock or powder. It is converted to
larger projects you can use a hand-held
ants include penetrating oils such as lin
"plaster of Paris" by heat. Gypsum is
spray gun powered by a gas-driven com
seed, hemp, caster, or coconut, and ani mal
Building Colloquium,
readily available available at build ing supply s tores,
pressor . Screen t he mi x thr oug h a 1/8-in ch
urine and blood, all of which oxidize and
Kingston, New Mexico.
and it can be applied directly on top of
screen to eliminate any lumps that might
harden the surface.
earthen plaster, since it is breathable. Due
clog the machine. This spray mix is often
Certain sealants may be mixed and ap
to its softness, it can only be used on inte
made with wheat flour paste as a stabilizer
plied as one layer, but different sealants
rior walls. It doesn't shrink or crack when
(see page 96 for the wheat flour paste
should never be layered over one another,
dry and sets very fast, which can be an ad
recipe).
as they could be incompatible and peel.
work fast when applying it to a wall, but
SEALANTS
waterproof sealant in their finer forms,
the technique is not hard for nonprofes
Sealants can also be used as nonstructural
but too muc h p ure bind er will not be du
sionals to learn. Gypsum is acidic, and has
stabilizers, but they are called sealants be
rable. Filler (sand, silt, or gravel) gravel) sh ould be
a low embodied energy compared to Port
cause they seal the earthen plaster—that
added to it to make it solid and hard.
land cement, but in premixed form it is
is, they are not mixed into the plaster dur
Sodium silicate dissolved in water is
relatively expensive. Gypsum plaster can
ing the construction process but are ap
known as water glass. Water glass can be
also be mixed as 1 part gypsum to 2 parts
plied like a pain t or a finish plaster once
used as a sealant with certain soil types, but
sand for more texture and lower cost, or it
the original plaster has dried.
has been known to react very differently
vantage or disadvantage—you need to
Binders such as clay can also be used as a
Cedar Rose demonstrating the spraying of a mud mixture at the Natural
WEATHERPROOFING AND FINISHES
94
layer. Potassium silicate is made out of
als in combination with poor ventilation; this phenomenon can
quartz sand and potash and binds itself
damage the health or at least affect the comfort and performance
chemically with silica when applied, which
of people living and working in newer buildings.
is good for surfaces that contain sand. Sili
Like cement, modern waterproof masonry paints, emulsion
cates also bind mechanically in grooves in
paint s, an d vinyl wallpaper s all slow do wn or pr event t he evap ora
the surface of the plaster.
tion of moisture from the wall, which often leads to the render or
Before applying, thin silicates with wa
pain t separ ating from the surface of th e wall , and water tra pped
ter: for example, 1 part potassium silicate
between the wall and the pain t can b e harmfu l to the wall itself,
to 5 parts water.
95
especially if the building is constr ucted of materials such as wo od or earth that can deteriorate when wet.
inside, you can coat them with "breathing"
Paint consists of pigments, extenders (also known as fillers), and binders. Pigments and extenders comprise 75 percent of the total quantity of paint. Binders comprise 25 percent. Pigments color the
paint s to give ex tra prot ectio n or color. I
filler. They can be different minerals or plan t powders. It is better
learned about this subject from Swiss
to use water-based p aints on walls, because these allow for vapor
PAINTS
As well as plastering earthen walls on the
The Steens' residence, Canelo, Arizona.
with varied mixes of earth. It is not suitable
paint er Reto Messner. Natu ral pain ts de
diffusion and breathability. Extenders are a kind of paint "filler."
for clay soils, but has proved useful with
rived from plant and mineral materials
Extenders can include whiting, obtainable at paint or ceramic
sandy soils. Sodium silicate is fairly cheap
have subtle colors, pleasant scents, and
stores; barium sulfate; kaolin; marble dust; chalk; and diatoma-
and is available in many parts of the world.
help create a healthy indoor environment.
ceous earth.
It acts as an impermeabli zing agent after a
Since only a few decades ago, the petro
Binders can be water based or oil based, depending on the re
curing perio d of seven days. It is soluble in
chemical industry has largely taken over
quirement. Examples of water-based binders include clay; casein
water, but can be rendered i nsoluble by al
pro duct ion of oil-ba sed and water- based
(milk protein), which is very strong when dry and will not come
lowing it to react with slaked lime. Thin
pain ts. They not only aban done d t he tra
apart; water glass; lime cellulose glue; starch glue (corn s tarch) or wheat paste; and lime.
sodium silicate with water prior to mixing
ditional view of paints as a breathing skin,
with earth, otherwise too many "micro fis
but have also intr oduc ed syn thetic chemi
Limewash, also called whitewash, is a water-based pai nt that has
sures" will result, causing a strong suction
cals that can be very harmful to us. In ad
been used for centur ies, ordin aril y re-co ated every year or so. Ad ditives to limewash to make it more durable (but less breathable)
of water. Another silicate used to make
dition to being concerned about the pollu
plasters impe rmeab le is potassium silicate.
tion generated by industrial paint manu
include linseed oil, tallow; and proteins such as egg white, blood
Potassium silicate can be dissolved in wa
facturing, increasing numbers of people
plasma , o r c asein. See page 97 for a more detailed discussion of lime paints.
ter to make a liquid, then used to seal and
find themselves affected by the vapors
waterproof mud plaster. The coating is
given off by modern paints as they dry,
clear in color, allowing the full beauty of
and even by the low levels of volatile or
the plaster to show. When put on top of
ganic compounds (VOCs) that continue
lime plaster, potassium silicate reacts with
CLA Y
SLIP
O R A L I S
to outgas afterward. Sick building syn
Alis is a clay-based paint tradition ally used over earthen plasters on the interior of adobe houses. Alis can be of any desired color, and
the calcium in the lime and the carbon di
drome has now been widely recognized to
when dry it makes a durable finish. I learned about alis from Carol
oxide in the air, creating an impervious
be the result of mo der n synthe tic mate ri-
Crews of Gourmet Adobe in Taos, New Mexico.
Painting with clay paint over an earthen plaster on a straw bale wall in Casa Chika, Kingston, New Mexico.
WEATHERPROOFING
96
AND
FINISHES
pancake batter. When the pot of water is
Application
sure that it is th oroughly premixed by add
mixture to make the pot almost full, and
Before application, make sure the wall sur
ing it to a little warm water in a jam jar,
stir the mixtur e well.
faceof your eart hen plaster is totally dry, as
then seal the jar's lid and shake vigorously.
any moisture could leave water stains in
Add the pigment to the limewash, and stir
the finish. Start applying the paint with a
and sieve it again. To get a really white fin
brush at the top of the wall so you do not
ish over an earthen plaster, you will prob
come translucent. Take it off the heat. The total proportion of water to flour should be about 6 parts water to 1 part flour paste. For mixing the plaster dilute this wheat paste to a good consistency.
ably need at least three coats. Limewash
get drips. Most walls require two coats. Make sure
turns very white only when it is dry, and if
the first coat is completely dry before the
pigment has been added, the final coat will
second is applied. When the second coat
turn about seven times lighter than when
becomes "leather hard," take a damp
it is liquid. Always wet the surface of the
Fill a 5 -gallon bucket three-fifths full with
(squeezed-out) sponge and a bucket with
earthen wall before applying a limewash.
3 parts water to 1 part cooked flour paste.
warm water and start to sponge the wall in
For the first, slightly thicker coat, add
circular movements. This will smooth out
Additives to Limewash
to the diluted flour paste liquid a mix of 3
the brush strokes and clean the paint of
These include:
stirred and stiff.
•
Add earth or
An earthen plaster
To Make Alis Clay Paint
shower wall painted Arizona.
fine kitchen sieve. If pigment is desired, be
vigorously boiling, pour in the flour-water
It should thicken immediately and be
with lime, Canelo,
97
linseed oil, and
If white alis is desired, Carol uses white
parts clay to 2 parts mica to 1 part fine sand.
any pieces of straw or flakes of mica that
kaolin clay as the binder, because it is inex
(If no mica is available, substitute fine
might have been added to the mix for spe
pensive and can be purchased in large bags
sand.) Keep adding these proportions un
cial effect. When the sponge begins to feel
•
from a pottery supply store. She uses
til the mixture is the consistency of heavy
dry, wet it and squeeze it out again. When
• molasses, to increase penetration
ground mica in a fine powder form or fine
cream.
you are finished, you can save the leftover
casein glues, or flour paste, as binders salt, to improve durability into an earthen wall
sand as the extender, and straw or mica
For the second coat, add to the diluted
paint for later repair to any minor damage
•
flakes for added texture and glitter. To
flour paste a mixture of 1 part clay to 1 part
by drying it out on a tarp in "cookies." To
• linseed oil or tallow, to increase
make the paint thicker, especially in the
mica. Again, keep adding these until the
reconstitute, simply add water to the dri ed
first coat, a small amount of fine sand is
mixture is the consistency of heavy cream.
paint until the appr opriate consistency is
obtained (Kennedy 1 9 9 9 , 9 3 ) .
added to smooth out irregularities in the
A little powdered milk (with casein)
plaster surface. As filler, Carol uses cooked
will thicken the mixture and makes it
flour paste in a proporti on of 20 to 25 per
somewhat tougher. Some finely chopped
LIME
cent of the liquid. Pigments or colored clay
straw or large flakes of mica can be added
If possible, find a source for ready-made
can be added to white alis to give it color.
alum, to improve adhesion water resistance
Recipes for Water-Resistant Whitewash Whitewash with oil or tallow. For exterior
PAINT
OR
WHI TEW ASH
Mix chalk and
surfaces, the addition of linseed oil or tal low (animal fat) makes the whitewash
for an interesting texture. Colored clays or
lime putty (matured for a minimum of six
more resistant to water. According to "Ap
pigments may also be added to create dif
weeks), as this is the easiest, safest way to
propriate Plasters, Renders and Finishes
To Cook Wheat Flour Paste
ferent colors. If colored clays are added,
buy the material, or mix bagged hydrated
for Cob and Random Stone Walls in De
Set a pot two-thirds full of water to boil on
they can replace some or all of the kaolin in
lime. Limewash is lime putty and water
von," published by Devon Earth Building
the stove. In a mixing bowl, whisk together
the recipe. If mold is a problem, it is advis
(see page 84 for more on lime putty). Mix
Association, use no more than 1 table
another one-third proportion of cold wa
able to add some dissolved borax powder,
the putty and water together to a consis
spoon of linseed oil or tallow for 2 gallons
ter with some flour to a consistency of a
which will make the paint alkaline.
tency of skimmed milk. Sieve through a
of whitewash. Add the oil when the lime
knead until well
plant pigment as desired, and use for filling gaps and puttying windows.
9
8
WEATHERPROOFING AND FINISHES
99
and water are slightly heated. Continue
1 pound clean glue in water, and add this
resistant. When it is mixed with an alkaline
Mix together ¼ cup ( 2 ounces) casein
stirring and heating slightly until the mix
solution to the mixture. You may also add
substance such as borax, it will react and
powder with 3 o unces of warm wat er, a nd ideally let sit for two hours or overnight.
coloring matter to give the mix any shade
form a gluelike solution that can be used as
you please. Apply the limewash while still
a binder in paints or plasters, or as an ac
(If homemade quark is used, it does not
Whitewash with linseed oil and milk. To
warm, with a whitewash brush—except
tual glue (see page 9 8 ) . If the casein paint is
need to be mixed with water.) Mix the
increase the water resistance of white
when particular neatness is required, in
used on top of lime plasters it does not
casein solution with ½ cup (4 ounces) of
wash, fill a container with 4 quarts of
which case use a paintbrush.
need to contain borax, as the alkalinity in
bor ax dissolved in ½ cup (4 ounces ) of
the lime will activate the casein.
warm water to produce the binder mix
ture has blended.
milk, add 1½ cups of linseed oil, and stir
This recipe is from a book by Sam
well. Add lime and stir continuously un
Droege first published in 1861 and found
til the mixture is creamy, of a paintlike
on the Internet (see the bibliography).
consistency. Some Old Limewash Recipes
To make whitewash that will not wear
Casein can be purchased. One com
ture. (Borax is an alkaline soap; do not
mercial brand is called Auro (see the re
dump in your garden.) This mixture will
sources list). You can paint your house us
becom e a sticky pas te a nd i s also know as
off, make the whitewash in the ordinary
ing about 2 pints of casein, as it goes a long
casein glue, which will lose strength over
manner, but then place it over a fire and
way. You can also make your own casein
time and must be kept refrigerated.
with simple ingredients.
If you are interested in trying out working
brin g to a boil . Then stir in to each gal lon a
with lime in a more primary form instead
tablespoon of powdered alum, ½ pint of
To make casein (also known as quark or
ter and mix until the solution is like pan
of premix, here is a recipe for a brilliant
good flour paste, and ½ pound of glue dis
milk curds) at home for use as the binder
cake batter. This can be used as a durable
whitewash that will not rub off, and which
solved in water while it is boiling.
in paint:
bears a gloss like ivory. Take 5 or 6 quarts
To this casein binder add 8 cups of wa
glaze or paint. (The binder mix when di
This wash looks as good as paint, is al
Mix 1 quart nonfat or 2 % milk and 2
luted can also be used to mix a durable
clean unslaked lime, slake with hot water
most as durable as slate, and will last as
teaspoons low-fat sour cream. Stir well.
plaster. ) When makin g tran spar ent pain t
in a tub, and cover securely to keep in the
long as paint. The recipe comes from the
Let sit in a warm spot for two days until it
(a glaze) for use on top of a lime plaster,
steam that's generated by the slaking.
Building Biology and Ecology Institute of
thickens or curdles. (If it does not curdle,
you do not need to add borax, since the
When the lime mix is ready, pass it
New Zeal and (see th e res ources list) .
warm it up or add vinegar to make it
lime will activate the casein.
through a fine sieve, and add ¼ pound whiting, 1 pound good, pulverized sugar,
CASEI N
and 3 pints rice flour, first made into a thin
Casein can be used as a binder or stabilizer,
paste. Boil this m ixtu re well, t hen dissolve
to make paints more durable and weather
Here is an old recipe for casein glue.
curdle.) Separate the curd s from the whey
To make this glaze into an opaque pain t,
by pou rin g the mixt ure thr ough cheese
mix pigment with an extender such as
cloth placed in a sieve.
chalk or any other inert white powder to
What you have left is known as quark,
make a paste. Then add this mixture to the
which contains 7 to 12 percent casein, the
bind er in a rati o of 25 percent binder to 75
right proportion for use as binder in the
perce nt extende r w ith pigm ent.
paint . Do not leave t his mixt ure to stan d
You can also make a water-based casein
for too many years, as casein loses strength
emulsion that is more water-resistant us
with time.
ing quark and lime. Mix a quantity of skimmed-milk curds (quark) with about
Mix skimmed-milk curds (quark) well with 2.5 percent quicklime. Use after one hour. Apply to both surfaces to be g lued toge ther and set unde r pressure for twenty-four ho urs. The mixture
Recipe for Interior-Exterior Casein
20 percent lime to o btain casein glue, then
should be remain useable for about three days on wood, cork, paper, or heavy wallpaper.
To make a durable casein glaze or paint
thin with water until it becomes a creamy
that can be used inside or outside and not
brew. This can be used for several days.
wash off in the rain:
Add 2 to 3 percent linseed oil to increase
10 0
WEATHERPROOFING
AND
101
FINISHES
adhesion and durability, especially for ex
is reasonably water resistant, but if ex
Remember, cement plasters are very
terior application. In addition, you can
posed for a long time to mois ture will
brit tle and will tend to crack du e to subtle
also use diluted casein paint as a primer,
eventually deteriorate.
movements of the whole structure, there
The wear of the finishes is affected sig
To make oil-based casein paint, add oil
fore requiring repair. Repairs of cement
nificantly by the materials you choose, the
wiping off after only a few weeks. Another
to a casein binder (see the recipe above)
stuccos and renders will always be visible
quality of the application, the location of
way to improve the adhesion of this paint
very gradually, as in making mayonnaise.
unless the whole area is repainted.
the house, as well as the overall design of
is to add honey to 10 0 parts curd, 50 parts
Mix a maximum 2 5 percent of volume of
Papercrete (fibrous cement made of cel
the house and whether there are any chil
water, and 20 parts lime.
oil into the mixture; 15 percent is usually
lulose mixed with cement or lime; see chap
dren or animals around, in which case
good, so test the paint on a sample patch
ter 1) can also be applied as a plaster directly
more house maintenance is generally nec
before more oil is added for shine . The
on earthbags. Papercrete is still at its ex
essary. Annual replastering does not have
mixture will eventually start to get creamy.
peri ment al stage, but this seems to be a
to be a chore, but can be turned into a fun
which will increase durability further—no
Application
If casein paint is sucked into the plaster
der, therefore it might not crack as much and may be easier to apply and repair.
right away and the desired effect is to be a
To make casein- or oil-based limewash,
material that is water-resistant (not water
social event involving the whole family or
glaze, it is necessary to prime t he wall first
mix 1 ounce limewash (lime putty mixed
proo f), therefo re suite d t o most climates ;
even the neighborhood.
with a thin mixture of casein binder and
with water) and 5 ounces casein powder or
insulative; and not as brittle as cement ren
water, and allow it to dry. When the paint is
1½ ounces linseed oil.
applied the water in the paint should be
Paint this limewash onto fresh lime
absorbed, but not immediately. As a prim
plaster that is no t totall y dry. You must use
ing binder, alum is especially appropriate
thin coats. It is best to use linseed oil for the
for gypsum-plastered walls. If the paint
first coat, followed by casein, because casein
continues to dust off, it does not contain
limewash is harder than oil limewash.
enough binder, or the wall is not primed proper ly. Too much bind er can create a glassy surface, which can flake off.
M AINTE NA NCE
The annual maintenance requirements for a plastered building depend on the nature
OIL- BASE D
PAINTS
of the finishes that were used. If the plaster
Linseed oil (from flaxseed) is a good oil to
finish is made of earth, maintenance is re
use in oil-based paint. This is a "stand oil,"
quired at least every two years. A thin coat
which is an important factor in making
of earthen plaster should be reapplied on a
oil-based finishes, because it oxidizes—
dampened wall surface. This is best carried
and dries—when exposed to oxygen. Ac
out during the summer months. If earthen
cording to the Canelo Project's Earthen
plaster has been sealed w ith a c appin g of
Floors booklet (see the bibliography), in
lime plaster, an annual fresh coat of white
the "old days" oils were left to stand ex
wash will maintain the finish well, but this
posed to the air t o p rodu ce the dryi ng ef
is not absolutely necessary, as well-ex
fect. However, they can now be produced
ecuted lime plasters will last many years
by injecting oxygen in to the oil. Linseed oil
before they need to b e r epaire d.
OTHER INTERIOR WALLS, FLOORS, AN D FURNISHINGS: BUILDING
WITH
CLAY
nce the structure of an earthbag
O
adapt to any shape. In a circular earthbag
house is complete, it is possible
dome shape, where straight and square
for the interior of the house to
furniture can be difficult to accommodate
have conventional furnishings, just like
and expensive to custom-make, earthen
any other house. More often, however,
materials are mo re flexible and less expen
those who have gone to the trouble of find
sive, allowing you to design the interior in
ing out how to build an earth house are in
a complex or simple way, using straight
terested in using natural materials and
lines or curves as desired.
earth-based techniques for completing the interior, in order to create an especially
FINDING
healthy and beautiful home. This can in
BUI LDI NG
AN D
ANALYZING
SOILS
clude partition walls, ceiling treatments,
As we consider guidelines for soil analysis
insulation, floors, and furniture. In this
pri or to b uild ing wit h clay -earth m ixtu res,
chapter, I refer to building materials and
readers will once again appreciate earth-
techniques such as clay-earth mix, straw-
bag con str ucti on for its s implicity, as ther e
clay, cob, and adobe, which were intro
is no need to understa nd the complexity of
duced in chapter 1. In describing these
the soil and its clay content, since the bags
techniques, I emphasize the need for clay
themselves provide a form to hold the
as a binder, as this is the most crucial in
earth in place, whereas when building in
gredient when building elements that
terior partitions, benches, ovens, and
Facing page: Earth-
must maintain their structural integrity
earthen floors, the binder-to-filler propor
plastered shelving
without exterior forms. Clay generally
tions are critical, because these structures
straw-clay blocks and
bind s toget her filler materi als su ch as sand ,
need to maintain their own form, with no
carrizo decking.
straw, and earth.
bag or othe r exteri or form to hold the
The advantage of using earthen materi
shape.
als for furnishings on the ins ide of a house
Due to the vast variety of soils, there are
stems not only from the beauty and health
no universal recipes for making good clay-
benefits of earth , but also its ability to
based mixt ures such as cob or ad obe. You
being constructed with
BUILDING
104
WITH
CLAY
105
can ask the people who have already built
dumping g round, which might be far away
pebbles , will settle at the very b ott om of
should be made into small patties or adobe
in the area where you want to build what
and therefore incur extra charges. If you
the jar. Then the sand and the silt (which is
blocks for c ompar iso n.
mixtures have worked for them. It is cru
can take this "waste" material off a
a finer version of sand) will settle, leaving
The first sample should be pure earth,
cial to know your soil before using it for
builde r's h ands , you may be able to obta in
the clay (the smallest particles of earth) as
to be used as a control, followed by samples
construction. For this, homemade tests
clay for a good price. Certain plants indi
the top layer. From this simple test we can
with 10, 20, and 30 percent of added sand.
can be carried out. There are several char
cate the presence of clay soils. For example,
estimate the per centage of clay in the soil.
acteristics to look for, including particle
the group of plants called horsetail or
size (ranging from fine silt and sand up to
scouring rush (Equisetum) suggest clay
Testing by Hand
rough aggregate such as gravel), plasticity
soils (Andreson 1 9 9 7 . When the earth is
There are numerous tests that can be car
tions. If th e soil has a high clay content, you
(the capacity to retain a shape, which per
very dry and many irregular cracks have
ried out on soils to check if clay is present.
may need to add more sand as a filler or
mits sculpting of the material), compress
appeared on its surface, this indicates the
Rolling and pressing the clay between the
more fiber to inhibit cracking.
ibility (to increase adhesion, especially
presenc e of clay. This is easily seen at t he
fingers will give an indication if the soil
When a sample indicates a good mix for
important with techniques such as pro
bot tom of puddl es or dri ed-u p pon ds.
contains any clay. If a thin "sausage"
buil ding, it will not crack. But not all
duction of compressed adobe blocks), and
Other landscape clues for the presence of
(about ¼ inch or 4 millimeters thick) can
cracks are bad. For adobe, the California
acidity or alkalinity (which affects the way
clay are described in Michael Smith's
be rolled and does not crack very much
Building Code allows cracks up to 2¾
book, The Cobber's Companion (see the
when slightly bent, the earth contains high
inches (7 centimeters) long and 1¼ inches
bibli ograp hy).
quantities of clay. If it cracks, it probably
(3 centimeters) wide (Khalili 1986). When
contains a larger quantity of silt. Another
dry, a promising sample can be tested by
way to test soil by hand is to make an egg
twisting it with your hands to try to break
shape, then crack it. If it resists cracking, it
it, or by droppi ng it from knee height. If it
various materials combine). Prior to beginning to build with earth, it is impor tant to unders tand the best ways of finding, extracting, and mixing the
The best way to begin to know your soil is by making several tests with samples.
most resilient blends of clay and other materials. The soil should be obtained
Jar Test
does not break upon impact, then the earth mix is right.
Pour several handfuls of earth into a large
mainly silt or other more granular par
gardens), and must be free of all organic
glass jar half full of water. Shake the jar well
ticles of soil.
matter.
and let it sit until all the particles settle. The heaviest particles, such as rocks and
bot h fibers and sand in varied prop or
is clay, whereas if it cracks easily it is
from below the topsoil line (topsoil is for
There are a number of ways to find clay.
Repeat the test, adding fibers such as straw, grass, hair, or textile strands, and then add
If the local soil does not contain enough clay to bind together properly, it is possible
TH E
RIG HT
MIX
that stabilizers are required. These need to
Many conclusions may be drawn from the
A good construction material must have
be te sted at th is stage by being added into
geological situation. Purchase geological
clay and sand in the right proportion. The
the mixture in varying quantities.
maps of the area or visit the geology de
more filler that is mixed with the clay, the
To answer the question of what makes a
par tme nt of a univers ity o r a gover nment
more evenly distributed the cracks that re
good building mix, here are a few pointers,
-floating organic matter
institution to request assistance. Consult
water
local brickmakers or potters, who are nec essarily very conscious of fine distinctions
clay
silt
sand
among earthen materials. Investigate the
gravel
availability of clay on conventional con
sult from drying will be. The more the
although it is important to note that every
straw is added, less sand may be needed,
mix should first be tested by making small
because straw takes up the shrin kage,
samples and observing them when dry,
therefore stopping the cracks.
pri or to any ap plica tion.
Always make samples, since this is one
struction sites, where clay is often dug up
A jar test to estimate percen tage of clay in a soil
of the most effective ways of being sure of
during excavation and transported to a
sample.
your soil's limitations. A set of samples
•
To form a durab le surface and create a mix sticky enough to adhere, you may
BUILDING
io6
WITH
CLAY
107
You will also want to carefully control
According to Devon Earth Builders,
the clay content, and/or add some
the type and size of filler or aggregate that
traditional English cob mix contains clay
type of stabilizer.
need to mix more thoroughly, increase
you use, taking into consideration the in
and aggregates in the following propor
• To minimize shrinkage and therefore
tended function of the mix—for example,
tions:
cracking, you can reduce clay, add
whether it is for the structure of furniture,
more sand or other aggregate, keep
the filling out or evening out of a base plas
fine course sand
25-30%
water content as low as possible, or
ter, or the final smoothing out of a finish
silt
10-20%
add more fiber such as straw and
plaster. The finer the desir ed appear ance,
clay
10-25%
other grasses, cellulose, or other plant
the finer the added aggregat e, filler, and fi
or animal fibers.
bers need to be.
• To increase water resistance as much
Also, a more structural eart hen mix can
It will also contain fibers (as much as the mix can take without ceasing to ad
as possible and slow down erosion by
have a large range of particle sizes, from
here) to reduce cracking and increase the
driving rain, you can add a good
silt to gravel, as the filler material, and "fill
insulation value. Sufficient straw in the
distributi on of aggregate sizes, fibers
ing in," "evening out" plasters can be made
mix provides a level of thermal insulat ion
such as straw, and/or stabilizers
using more of the long straw additive in
that is better or equal to the insulation in
derived from plant, animal, or mineral
order to be more reinforcing and provide
many conventional houses. In England,
sources (see chapter 6).
more s culptural capacity. The final layer of
traditionally the fibers used were wheat
plaster can have just fine sand mixed in
and barley straw along with hay, twigs, and
poros ity of an eart hen mix, which are
with the clay, as well as finely chopped
other organic material including animal
or cob for building is all principally the
necessary to permit moisture to
straw and stabilizers if desired.
hair and animal dung.
same process. The ingredients might vary
• To increase the permeability and
A cob shelter built
My own favorite mix for a thick first
Correct mixing of the material is as im
slightly, but once the recipe for a particu
coat of plaster and for sculpting is quite
por tan t as th e actual c onst ruct ion pro cess.
lar type of earth is established, these pro
frost damage, an earthen mix needs
simple and works with most clay soils. In a
If too little water is added, the necessary
port ion s can be used for any of the above
a good distribution of aggregate,
wheelbarrow (as described on page 1 0 8 )
distribution of clay throughout the soil
techniques. The ingredients might include
straw, and anything else that will
combine a soupy mixture of clay soil with
will be difficult to achieve, and the cob
varying proportions of straw, depending
create air gaps.
as much long or chopped straw as the mix
lumps will be difficult to compact when
on the coarseness of the earth and sand.
ture can take and still stick together, along
placed on th e wall. In th e past, co mpact ion
Earthen plasters or floor finishes will re
If you are carrying out sample tests with
with just enough s and to give it some body
was achieved using the worker's boot, so
quire the mix to be sifted, for a fi ner f inish.
evaporate and to allow for expansion of freezing water in order to avoid
stabilizers and are not getting the results
and prevent hairline cracks for the finish
that each cob is well heeled-in and thor
Cob for building may require more straw
you might expect, try testing the pH of the
ing layer. (Chopped straw will be easier to
oughly trodden between each course. Ex
than adobe requires.
soil, as not all stabilizers react with soils of
manage than long straw during smooth
cessive moisture dilutes the soil to a
ing.) If the first layer is fairly thick and
Many different ways have been devel
all types. For example, if the clay is more
porr idgy state, maki ng cons truc tion im
acidic, it should react beautifully with
even, the second layer can be thin, with
oped throughout the years in different
possib le; i n such cases, mo re dr y mix and /
more sand substituted for straw, and in
part s of t he world, but they all have the
lime, an alkaline, forming a more neutral
or straw can be added.
side the house a stabilizer such as wheat
same aim—evenly distributing the vari
and creamy mix for an external rend er (see chapter 6 for more on stabilization).
paste added .
Getting the right mix for earthen plas ter, floors, or furniture and making adobe
ous materials that make up the mix and creating a moist, pliable mass of earth.
during a workshop led by Sunray Kelly and Carol Crews, Rico, Colorado.
108
BUILDING
WITH
CLAY
109
In the traditional way developed over centuries in Devon, En gland, once proportions are identified through testing and mak ing samples, the desired earth mix is
sieved, up to half an hour might be neces sary. When the mix is ready, work it thor oughly with your hands, stirring around so that the sand, clay, and water are well
spread out in a bed approximately 10 0 millimeters in depth
mixed into a soupy consistency. At this
on a thin layer of straw. Water is then added and a second,
stage, as much straw can be added as the
thicker layer of straw is spread evenly on top. (About 25 kg.
mix can take and still cohere, kneading
of straw per cubic meter of soil— 1.5 to 2 . 0 % by weight—is
thoroughly with hands or with feet. For
considered adequate.) The straw is then trodden into the
foot mixing, dig a pit to use instead of a
soil, which is turned several times, more water being added
wheelbarrow.
as required. Thorough treading of the mix (traditionally by men or animals) is vital because it ensures even distribution of the clay and renders the material to a consistency and a state of cohesion suitable for building. The quantity of water used will vary according to soil type but is usually in the
Another way of mixing, which I learned at the Natural Building Colloquium, in volves placing the earth mix in a pile on top of a plastic tarp. Water is added, and two people hold the tarp at opposite ends,
excuse to get muddy. And it is amazing to see how quickly adults turn into children when working with "mud," especially for the first time. Therefore to replaster your house once a year could turn into a huge par ty and an excuse to enjoy yours elves with your friends and relatives. TH IN
PARTITIONS
CEIL ING
AND
PANELS
As an alternative to conventional gypsum drywall, extensive research is underway to pro du ce str uct ura l mem be rs ou t of clay-
range of 10 to 1 2 % by weight. If too little water is added the
leaning and pulling to each side, shifting
necessary distribution of clay throughout the soil, will be
fiber composites. Prefabricated fiber com
their grip on the tarp to roll the mixture
posi te bo ard is a form of i ndu stri al dry -
back and forth , an d s top ping from time to
boa rd deve lope d in the pas t few years
difficult to achieve. (Devon Historic Building Trust, 1992.)
time to add more water and straw. This
Mixing with bare feet.
loved activity, where not only the adults bu t the chil dren can all join in a nd ha ve an
The Taos Pueblo way of mixing is similar to the traditional
technique requires a substantial amount
Devon way, except that the warm sunny summer weather allows
of effort, but, as when mixing with feet,
the people to do it barefooted in a dug-out shallow pit.
your back remains straight, whereas mix
Athena an d Bill Steen, while in Mexico worki ng on the Save the
ing by hand requires bending over a
Children Foundation project, were taught by their Mexican col
wheelbarrow. Remember that the thor
leagues how to mix the "no-effort way." Simply half fill the con
oughness of the mixing contributes to the
tainer you are mixing in with water (most likely a wheelbarrow),
bin din g st ren gth of th e r esul ting mix tur e.
then use a shovel to sprinkle the dry earthen mix into the water in
An endless variety of mixing methods is
the proportions you have derived from testing (or use pure clay).
constantly being developed and refined,
Make sure the distribution is even and not too thick. If the mix is
each one suiting different climates and in
not ready, alternate shovels full of the necessary clay, earth, and/or
dividuals. Ian to Evans and Linda Smiley of
sand. Once earth covers the top of the water, go and have a cup of
the Cob Cottage Company, who have de
tea or a lunch break. Let it sit long enou gh for the soil-clay mixture
voted the past several years to the revival of
to absorb all the water. The speed of absorption depends on the
cob in the United States, believe that you
fineness of the clay-soil particles (for instance, whe ther it has been
should always mix cob when happy. This
sieved). After a few minutes, test the mix by sticking your finger
way the building is built with good as op
in. When ready, it will be smooth and creamy. If it is still lumpy an d
pos ed to b ad en ergy, e nha nci ng its quality .
hard, or partly dry, it needs to sit longer. If the soil has not been
Mixing earth usually becomes a much-
(Andreson
1 9 9 7 ) .
This board is made of
Mixing the clay.
BUILDING
110
WITH
CLAY
111
fiber-coated, plant- fiber- reinfo rced
clay,
bor ax for firepro ofing
or stuffed into
heated regularly either by the sun or a
manufactured by applying clay to burlap
treated burlap bags, cotton, flax, or sheep's
stove, the thermal mass of the earth will
fabric (jute net). For strength, two or more
wool. Cellulose insulation made out of re
retain heat in the winter and coolness in
layers of reed mats are inserted crosswise,
cycled paper ground up and treated with a
the summer.
with alternating layers of clay paste. Fi
flame retardant can be blown in to cavities
For earthbag domes built in cold cli
nally, the surface of the board is covered in
betwee n rafters with a specially rent ed
mates, if desired the insulation can be in
burl ap and t ran spo rte d to a dry ing sta tion.
machine to insulate the ceiling or roof, and
corporated in the floor, ceiling, and final
Tests with this kind of board have shown
in timber frame construction, between
layers of the internal and external plaster,
excellent results with regard to fireproof,
studs in the walls (it is also available in batt
which can be significantly thickened to
soundproof, deformation, and diffusion
form). Hemp cellulose (fireproofed with
provi de a more insulat ive finish using a
values. Such boards could be used, for ex
mineral salts and called Canobite) can also
layer of straw-clay on the inside and pap er
ample, as a permanent form combined
be purch ased, e ither loos ely packed in bags
crete outside.
tional insulation
with straw-clay or blown-in cellulose in
or to be blown in. Wood-fiber boards can
materials create
sulation, or as ceiling panels (see Con
also be used for thermal and acoustic insu
environmental
struction Resources in the resources list).
lation (Tibbies 1997-98).
As mentioned above, straw can be coated
They can be screwed, nailed, and sawed,
To increase insulation value in an
To prepare straw-light clay, pour the
problems as a
with clay slip called straw-light clay and
clay slip on top of a pile of straw, tossing it
then plastered over as a finish. When a
earthen mix, straw, wood fibers, cork, and
used as insulati on in many different ways:
energy-intensive
smooth surface such as wood framing has
other air-trapping fibers can be used, ei
like a salad with pitchforks. Coat every
stuffed between rafters as roof or ceiling
to be plastered, burlap can be placed over a
ther added into the earthen mix or at
single piece of straw completely with clay
and destructive
insulation, placed in the floor using the
slip. To test if it is coated enough, take a bun dle of the mix and squeeze it—if it
Many conven
result of their
Straw-Light Clay An earthship (rammed
extraction and
wet coat of base plaster and allowed to d ry
tached in panels along the walls. Pumice,
rammed straw technique, or made into
manufacturing
before a final coat, or reed mats can be
perlit e, and other minera ls used for floor s
lightweight blocks to construct relatively
sticks together, it is ready. If time allows, it
used as lathe between sections of clay
and screeds can also be added as an aggre
thin but highly insulative walls.
boar d. And as n oted in ch apter 1, in teri or
gate to increase the insulating value of in
is then best left for a day or two under a
To make light clay, pure clay is necessary
part iti ons can be made with wattle and
terior plaster and ovens. One of the best
for maximum binding strength. The clay
insulating materials for corbeled dome
Another application for light clay is the
daub or with the rammed straw technique
has to be mixed with enough water to tu rn
technique of rammed straw, whereby the
processes. These materials can also cause health problems during installation or even after,
described below.
because of
tarp to mature and improve.
constructi on is pumice-filled bags (see the
it into a slurry called clay slip or liquid clay
profile of Kelly and Rosanna' s hous e on
mixture described above is used to con
(always adding the clay to the water, never
page 135), but this material occurs natu
struct walls and partitions. After being
water to the clay). If the mix is lumpy or
coated with clay slip, the straw-ligh t clay is
contains stones, it could be passed through
lightly rammed between the form boards
particle migra
INSULATIO N
tion and off-
Good insulation in a building can signifi
rally in very few parts of the world and is
gassing.There are
cantly reduce the heating cost. Insulation
costly to purchase and transport.
a 1/8-inch screen. The consistency should
(shuttering) with a 2 x 4 (or your feet) until
now natural
can be built into the walls, ceiling, roof,
Earthbag domes in sunny climates do
be such that when you dip the palm of
it is solid and not spongy. The forms can be
insulation
and in some cooler climates the floor (see
not require insulation, if the design pro
your hand in the mix no lines can be seen
materials for
moved up t o the next lift immediately after
the section on floors, page 115). It is a ma
vides for passive solar heat in the winter,
on your hand. The purer the clay, the
completion of each particular section. To
terial that will trap small pockets of air.
and openings are placed in a way that they
thinner it can be diluted due to its greater
preser ve th e ins ulati on pr oper ties (that is,
Natur al alternati ves to indus tria l fiberg lass
do not allow direct sunlight into the ho use
bind ing stren gth, there by achieving
include straw treated with potato s tarch or
in the summer. If the dome is lived in and
lighter straw-clay mix.
almost any situation.
a
trapped air in the straw), it is important for the tamping not to be too hard.
earth in tires) wrapped by straw bale insulation.
BUILDING
WITH
CLAY
113
112
east and west side, for example) and the Hybrid Earthbag and Straw Bale a pole tied to the earthbag wall providing air space (at intervals of 2 per bale) string that ties the straw bales to the earthbag wall
Straw bales are among the best value for
straw bale tied to earthbag wall earthen plaster covering the straw bales
earthbag footing for the straw bale wall
gravel trench
A house where two (east and west) earthbag walls are structural and the straw bales are a nonstructural insulating wall on the Detail section through an earthbag wall with straw bale wall for added insulation.
north side, with glazed frame construction on the south-facing front for passive solar heating.
insulation value of straw bales on the cold north side.
natural insulation, but unfortunately they
Straw is an annually renewable re
take up a lot of space. They can be used as
source, the waste produ ct of a cereal grain
floor or roof insulation on ladder trusses
crop, and can be easily grown and har
or as insulation for living roofs. Bales can
vested. Bales can also be made out of
also be used in conjunction with earthbag
tumbleweed, sudan grass, and ordinary
walls either as internal supplementary in
meadow hay, but straw is the best natural
sulating walls, creating a three-foot-thick
insulator due to its hollow stems that trap
wall, or as nonstructur al infill in combina
the air, and it is not attractive to vermin
tion with load-bearing walls or piers, cre
since it lacks nutrients. The straw bale
ating buildings that have the structural
technique represents an entirely distinct
stability and thermal mass of earth (on t he
construction system, which needs to be
strings to tie the bales are fed through tubes left in the earthbag wall
Three different ways of integrating earthbag and straw bale wall systems.
carrizo or other wooden poles sandwiching the walls
earthbag wall
Above: Building with rammed earth. Left: A rammed straw wall.
BUILDING
114
WITH
CLAY
115
understood as a system in itself before it
ture can also be used for stoves and ovens
can be properly applied in combination
by a ddin g less straw and more sand, per-
with earthbags, adobe, or cob. Straw bale
lite, or pumice to the mixture. These
cob with a flue from a woodstove coming through and warming them while the
structures can be load bearing or non-
earthen heaters can be sculpted with
stove is used, creating a "cozy" corner through the winter months.
load-bearing . A number of good books are
niches, alcoves, and benches to suit the size
available on straw bale construction (see
and shape of a house. By embedding a flue
the bibliography).
in an earthen bench, you can make a warm
In addition to being used in wall construction, cob can be used to sculpt furniture in a very freeform way—seating, desks, and shelves. Benches can be made of solid
existing wait stabilized earthen plaster slightly sloping to shed water
seating area. INTERIOR
For the interior partitions or even exte
DETAILI NG
Several earthbuilding techniques can be
rior walls where the earth has insufficient
used for sculpting furniture as well as for
bind ing s treng th to hold nails carry ing the
construction
cob
and
weight of fixtures, the installation of hang ing cabinets and other furnishings re
different straw-clay mixes, and straw bales
quires a nailer board that can be installed
can all be used to construc t the main struc
after the wall has dried. In preparation,
ture of sculpted furniture, sealed and
wooden stakes should be placed between
smoothed out with an earthen plaster,
the rows of earthbags before tamping, or
existing wall
then capped with lime, gypsum, or some
embedded in the cob or adobe with a led
earthen plaster
other clay paint finish for durability.
ger board attached across two or more
small
structures
The materials used for creating furni
stone as a border between the cob and the existing wall to protect the wall from moisture well-tamped earthbag
well-conditioned gravel and rubble
houses. Earthbags, rubble, cob, adobe, the
of
earthen plaster or sculpted cob can also have flagstone embedded in the surface and can be stabilized with linseed oil (in rainy climates covered with li me or limestabilized earth), stone or rubble
well-tamped gravelbags
Exterior cob bench.
Exterior earthbag bench.
cob wall to retain the gravel or rubble
well-compacted rubble and earth, or solid cob
stakes, which provide anchors for nailing.
possible flue from oven to heat the bench
well-compacted gravel
adobe or cob wall to retain the rubble
Interior heated bench.
Exterior cob seating.
Earth-plastered shelving being constructed with straw-clay blocks and carrizo decking.
Then a cabinet or other fixture can be at
rently being revived. In spite of the s tereo
tached with screws or nails to this ledger
type of "dirt floors," earthen floors need
boar d.
not be dusty, fragile, or difficult to clean. The right applicatio n of oil and wax makes
EAR THEN
FLOORS
For centuries, earthen floors were used all
earthen floors waterproof and almost as durable as concrete. Some of the earthen
over the world. Until recently, they were
floors I have seen have been walked on
the standard floors throughout the south
with high heels, and can take the pressure
western United States, where they are cur
of furniture. There is no o ne correct way of
BUILDING
116
WITH
CLAY
constructing these floors. The materials
troductory earthen floor booklet (see the
1. Base: This layer should be either undis
used vary according to availability, but the
bibli ograp hy); th erefore , I will only give an
turbed soil, or at least a very well-com
quality of the floor primarily depends on
outline of the construction method.
pacted surface, since it nee ds to be free of
117
all organic matter and unlikely to heave in
Floor, showing
frost, so that no movement occurs.
alternative insulation
the workmanship. It is possible to create
The floor should be poured during the
earthen floors that are durable and require
driest part of the year. It can take between
little maintenance, if certain basic prin
ten days and six weeks to thoroughly dry
ciples are understood. The method I
out. The layers of an earthen floor are as
learned from Bill and Athena Steen of the
follows (make sure each layer is fairly level
sary in very damp areas that cannot be
Canelo Project, who have produced an in
to minimize your wo rk on the final layer):
prop erly drai ned. The waterp roofi ng can
layer of bottles embedded in sand.
2. Waterproofing: This layer is only neces
be natu ral clay s uch as bent onit e (which should be tested prior to construction) or a synthetic damp-proof membrane.
6. Finished floor: The top structural layer, approximately 1 inch (25 millimeters) of trowelled clay-earth mix. The clay-earth
3. Drainage: To stop any mois ture from rising, this is a layer of 6 to 12 inches (150 to 300 millimeters) of washed gravel or
mix should be comparable to a good
course sand, tamped down well. If no
top layer will need stabilizer. Other o ptions
waterproofing membrane is used, the
include 4 to 6 inches (100 to 150 millime
gravel needs to be quite large—¾ to 1½
ters) of well-tamped clay-sand-soil mix or
inches (20 to 40 millimeters) in diam
2 to 3 inches (50 to 75 millimeters) of clay-
eter—to prevent the rise of moisture.
earthen plaster mix (see chapter 6), and should be troweled in two half layers; the
soil mix with psyllium (the mucilaginous powde red seed of the Plantago psyllium
4. Insulation: This layer should be 4 to 6
Earthen floor layers with flagstone embedded into the top layer.
plant , also used as a laxative ). F or nat ural
inches (100 to 150 millimeters) of straw-
stabilizers, hardening agents such as lime,
light clay or pumice, perlite-clay, or bottles
blood , or wheat past e can be added (see the
embedded in sand, well tamped.
discussion of stabilizers in chapter 6).
5. Subfloor:
7. Sealant: Apply several layers of an oil-
The aim of this layer is to
achieve maximum compaction on top of
solvent solution for added protection. Use
the insulation, in preparation for the fin
boiled linseed oil or othe r stan d oil, as
ishing layers of earth. It should be com
these are oils that dry well, and which can
pacted silty or sandy soil, the same as the
also be used for other ear then finishes. For
base. Thi s is the layer that ca n take radi ant-
the solvent, the least expensive is turpen
floor tubing. If a floor heating system is
tine, but you may use anything from com
used, the subfloor must be considerably
mon mineral spirits to more-expensive
thicker to provide adequate thermal mass.
odorless turpentine or pure citrus oils.
BUILDING
118
finished floor layers "evening out" layer of clay with sand and low-density of straw willow, hazel, or carrizo arches
WITH
CLAY
screeds. Pour the mix between them, and
can also be set with adobe mortar for ar
lay a straight board across the top of them.
eas of the house that get wet frequently,
Remove the board farthest from you, and
such as the kitchen, bathroom, mud
fill in the void where the board had been
room, or entrance hall.
with more mixture. Reposition the first board, level it, and keep going. It is best if
and 6 percent carnauba wax at 140 to 158
Sealants, Maintenance, and Repair
degrees Fahrenheit (60 to 70 degrees
The top layer should be completely dry before applying the sealant. To be most ef
finished floor layers
shape when each board is removed. For the
"evening out" layer
final layer, hammer in nails so their heads
fective, the oil-solvent solution should be
spruce or larch and 40 percent boiled
reed or straw-clay rolls floorjoist
are level with the height of the finished
heated, taking care not to reach the point
linseed oil.
floor. Use them for leveling the board, and
where it begins to smoke. Warming en
Add 30 percent balsam turpentine from
Increase linseed oil and reduce beeswax
courages deeper penetration of the oil
to make a softer mix. You may use citrus oil
into the floor. If the ambient temperature
instead of pine turpentine.
sealant will be better absorbed. Apply
"evening out" layer layers of carrizo
with a brush, and remove the excess. Each
floorjoist
coat should be applied only thick enough
coat 1 —apply full-strength oil
that it does no t begin to puddl e, for if al
coat 2 —dilute the oil with 25%
lowed to puddle it may form a skin on the
Examples of an upper
If you wish to consider c onstruction of
Celsius).
of the room with the floor is warm, the
finished floor layers
floor finish.
In a double-boiler with water in the bottom section, melt 24 percent beeswax
your mixture is not too wet and keeps its
pull them out as you go along.
floor with an earthen
119
solvent
surface, which will be prone to cracking.
coat 3 —dilute with 50 % solvent
Note that b oth oils and solvents are very
coat 4 —dilut e wit h 7 5% solvent
flammable and should be treated with Screeding.
an earthen floor for an upper story, a
caution when heating. Any brushes or rags used during application should be
straw-clay mixture can be used to fill in the
stored carefully in closed containers to
Each coat should be applied only after the previous one is dry. The floor should only need four coats to be sealed. For addi
space between the ceiling joists, as shown
Here are some other ideas for natural
above. Then the layers of earth can be
floors. Lay a gridwork of equal-sized 2 x 4
poured upo n that base as described below.
timbers before pouring the final layers,
It is better to apply the oil in a str onger
then fill the spaces between them one by
concentration in the initial coats, gradu
of maintenance will depend on the wear
one, leveling at the same time. The timbers
ally reducing the proportion of oil to sol
the floor receives, but for an average floor
Use screed boards as wide as the depth of
can be permanent or else removable when
vents in the following coats. The earthen
6- to 12-month intervals is sufficient. If
the layered floor, initially placing them flat
the mixture is "leather-hard," and the
floor is less porous with each subsequent
sheen is not important, the floor does not
near the wall where you will start pour ing.
voids can then be grouted with a different-
coat of sealant, but will accept full-
have to be recoated for many years.
strength oil at the beginning.
Construction
prevent spon taneous combustion.
tional sheen and durability, another coat can be applied periodically. The frequency
Remember to start at the farthest corner,
colored mix. An alternative to a poured
working your way out toward the door.
adobe floor could be sundried adobe
According to the Steens' Earthen Floors
resistant but waterproof, after the floor has
With an accurate level, keep checking that
bricks set in place like tiles with a mud-
booklet, the sealant coats can be diluted as
dried from the last application of oil, apply
each board is level as you use them as
sand mortar. Fired brick, tile, or flagstones
follows:
If you want the floor to be not just water
a coat of wax. Make a paste by melting 1
BUILDING
120
WITH
CLAY
121
part beeswax with 2 parts boiled linseed
bag walls, they should be encased in a
cover the wires with a thin strip of metal or
either set into grooves between courses or
oil. While the paste is still warm, ru b it int o
larger-diameter sleeve that is sloped down
plastic to keep the stucco from contacting
exposed on the wall surface for future ac
the floor with a clean rag. The wax layer
to the outside. That way if the inner pipe
the wires. Wiring that is plastered into a
cessibility and convenient servicing. The
will rub off over time, so reapply it every
gets a leak, the outer sleeve will direct the
wall is difficult to modify, so test your wir
other option is to consolidate all the wir
few months or once a year.
water outside the house where it can be
ing fully before plastering; or route your
ing on the interior partitions (if they ex
seen, instead of soaking the inside of the
wiring in conduit, which can be made out
ist), in the ceiling, or in raised floors with
wall without anyone knowing.
of plastic tubing or discarded garden hose,
floor outlets.
If cracks or other wear-and-tear begin to show on the floor surface, it is good to patch these places fairly quickly to avoid
Electrical wiring and J boxes can be
them growing larger in size. When con
placed as the rows of the earthbags go up ,
structing the floor, save some of the mix
or can be added in the grooves between
for later repairs, as it will be almost impos
courses before plastering. Cut 12-inch-
sible to match the color later. After clear
long (130 centimeter) pointed stakes out
ing the area that needs repair and crackup
of 2 x 4s to anchor the electrical boxes in
off all loose material, add some water to
the earthbag walls. After making a notch
the dry mixture and mix thoroughly. Then
for the box to recess into the earthbag sur
wet the damaged area, fill it in with the
face, drive the stake in. Even easier, place
mix, and reseal the surface as described
the stake in the wall between courses dur
above, with four layers of sealant.
ing the laying of the bags. You can screw the box to the end of the stake and place
ELECTRIC ITY
AND
PLUMBING
the wires between the courses of bag. Use
For electrical and plumbing utilities, it is
heavy-gauge, U-shaped wire pins to hold
safest to place all the service ducts that en
the wiring in the grooves. If you are using
ter and leave the house below ground level
cement plaster internally, you may want to
going through the foundations, to prevent freezing and to minimize damage if a pipe does fracture. This can be planned int o the design ahead of time, enabling the inser tion of plastic sleeves throug h the founda tion and floor where necessary during construction. A plumbing chase can also be created in partitio n walls and under the floor. Non pressurized drainpipes are safe to route through earthbag walls and can go directly out to a separate graywater system for each sink. If pipes must be run through earth-
Electrical box fixed to wooden stake for anchoring in earthbag wall.
8
THE
EARTHB AG
AD VEN TU RE
S
ince the inception of this book, numerous earthbag projects have been built. This chapter offers a survey of the earliest and therefore some of the most adventurous. These include
examples of the Hart's very experimental freestyle dwelling; the amazing demons tratio n of courage by Shirley Tassencourt, then in her late sixties; and Kaki Hunter and Doni Kiffmeyer's advance ment of the earthbag technique to true perfection. Each of these
projects yields tre mend ous insp irat ion and many lessons . SHIRLEY
TASSENCOURT 'S
DOM ES,
ARI ZONA
To my knowledge, the first earthbag domes to be actually inhab ited were built by Shirley Tassencourt with help from friends and relatives, including her grandson Dominic Howes. Shirley chose the earthbag technology because of its "magic" and her limited finances. As she is an artist who often sculpts with clay, earth seemed like a familiar medium. Between 1995 a nd 1997, Shirley built three earthbag structures:
first, a meditation dome, "Domosophia"; next, a main house dome; then , a rectangular-shaped libr ary with a conventional roof. The soil used to fill the bags was brought from nearby. The Meditation Dome
The meditation dome has an external diameter of 15 feet (4.5 meters)with 1½-foot-wide (45 centimeter) walls sitting on bed rock, a cement-stabilized row of earthbags below the rafters of the mezzanine level, and a reinforced concrete bond beam pinned to the wall, serving as the compression ring for the opening. Exte rior and interior plasters are cement stucco. The upper level was
123
THE
124
EARTHBAG
ADVENTURE
125
Section of the Meditation dome
Above: Th e first lived-in
designed to contain a small studio space
desert. Then as I sat in the dome at Cal-
son Dominic Howes, and a fun young married couple, Luther and
earthbag dome built in
with a 360-degree view of the surroun ding
Earth listening to Nader Khalili, I was ob
Cindy McCurtis. We figured it out as we went along. With four of
Arizona by Shirley Tassencourt with her grandson Dominic Howes.
sessed with wanting to be in such a cen
us working for five hours a day in the desert heat using small bags,
Here's how Shirley tells the story : "At the
tered, dynamic, revolving space. Being old
in three months we finished the essential dome, Domosophia. A
age of fifty-two, as a first-time contractor/
enough (sixty-nine) not to be hampered
carpentry crew made the 7-foot-diameter clerestory (with its 360-
owner-builder of a 1,500 -square-foot salt-
by reality, I went home and started the next
degree view); they brought the spidery structure out in a truck and plopped it on top . We covered it with chicken wire, tarpaper, and
land.
box on Martha's Vineyard, I thought I h ad
day on the Meditation Dome. Some ad
just made it under the dodderi ng line. But
venture, oh my! Lady luck hovered over the
as a retired art teacher and potter/sculptor,
total project—undertaken by me in my
I had another go at it in Arizona's high
late sixties, my nineteen-year-old grand
stucco, and voila- —I had my heart's desire."
Above: The skylight being constructed on top of the compression ring. Above left: The cost of materials for the main dome structure and finishes (without utilities) was about $6,000, primarily for cement and specially made windows, doors, and skylight. Insert: The library was built under a pole supported roof, which provided a cover for shade. Earthbags were used as infill, as in a post-and-beam construction.
126
Section and plan of Shirley Tassencourt's Main House dome. Note the double earthbag wall up to the mezzanine level.
THE
EARTHBAG
The Main House Dome
A L L E G R A
The second-story floor rests on a concrete bond beam, and the
A R I Z O N A
ADVENTURE
A HLQ UI ST' S
127
HOUSE,
mezzanine level has a sky view. No other foundation was needed,
This house is situated on the land shared
as the ground is bedrock. The earth was dug out 6 inches (150 mil
with Shirley Tassencourt in Arizona. It was
limeters), and a poured concrete slab finished with tiles. External
built by Dominic Howes, finished in 1997.
and internal plasters are cement stucco without lath; the uneven
It is an example of mixing alternative tech
surface of bags provides enough reinforcement and key-in points.
nology with conventional construction.
Again, here is Shirley's own account: "Emboldened by our suc
Buttressed earthbag walls stand on a con
cess, in 1995 in a hot September desert, we started on the second,
crete foundation, and are tied together
larger dome, this time built with an engineer's approval. It took us
with a bond beam supporting a timber-
five months and 5,000 small sand bags. This dome has a 25-foot
trussed roof. Allegra is very content with
footprint, with a double (42-inch-thick) earthbag wall 9 feet up to
her 625-square-foot house. The house
the base of the mezzanine level with earth rammed in the cavity,
took four months to build and cost 40,000
which is sealed with a concrete bond beam. The outer wall acts as
dollars, the biggest expenses being a con
a huge buttress, and could have been considerably smaller, but
ventional roof, foam insulation, concrete
there was little precedent for this kind of construct ion using small
foundation,
windows,
doors,
cement
bags. We hand-lifted 25,000 pounds of earth on straw-bale scaf
stucco, and labor, which was about one-
Above: Allegra's square
folding for our 20-foot-high building, crowned with a 5-foot-high,
quarter of the final cost. The floor is brick
house.
7-foot-diameter plexiglass skylight. Skylights offer gifts of sky and
on sand with floor-heating tubing in the
landscape unusual to dome construction. Twelve-inch PVC tubes
sand layer. The south-facing windows pro
throug h the second-floor walls plus a window-d oor to the balcony
vide passive solar heating; in fact, the in-
allow inexpensive fenestration and continuous air flow from two
floor heating system (regulated by a ther
doors below, which are open all summer. [Author's no te: In Ari zona, this skylight has to be covered in the summer d ue to the in
Left: Sketch plan of the house.
mostat) has only been used six times in the past three years in spite of cold winters.
tensity of the sun, and in winter it causes considerable heat loss. The skylight should be off-center, angled south.] "My grandson was an appr entice for the first dome, foreman on the second dome, and a contractor on our neighbor Allegra's house (see page 127). Domini c went on to build a large, rectangular earthbag- and roof-truss hybrid structure in Wisconsin. Here in Arizona, I and two other elder women have thirty acres off-thegrid. We embrace Permaculture, gardening till the grasshopper plague arrives in July. We do ceremonies, and connect deeply with the land through our fifteen-acre natural medicine wheel (made
timber truss timber wall plate for the truss to sit on concrete bond beam with contin uous reinforcement, pinned to the earthbags at intervals earthbag wall with t wo strands of 4-point barbed wire between
courses 2" (50 mm) of styrofoam insulation chicken wire to enable the external plaster to stick concrete footing
with big boulders marking the cardinal di rections on a circle). We want to encourage others.... If we can do this, anyone can!"
Section showing wall-to-roof junction.
128
HOU SE
Above:The finished house.
129
THE EARTHBAG ADVENTURE
BUILT
BY
DOMINI C
HOWES,
WISC ONSI N
The house is situated in an extreme cli
therefore, the treatment of the earthbag
mate where the temperatures range from
wall is carried out in a similar manner. It is
Structural section through the south wall.
Detail section through the south wall.
as low as -4 0 degrees Fahrenheit in the
almost entirely a conventional house with
winter up to the high 80s in the summer,
standard timber-frame construction and
The house under
with heavy rainfall through the summer
artificial foam insulation, but instead of
construction.
months . Designed by the client, it has two
using brick or concrete for the structural
stories where the second is of conventional
walls it uses the earthbags filled with the
construction, with high windows for pas
local earth.
sive solar access.
The earthbag part of the house took
This house was built by Dominic
three weeks to build. The floor area of the
Howes almost directly after construction
house including the first floor is approxi
of Allegra Ahlquist's house (page 127);
mately 1,500 square feet.
130
THE
EARTHBAG
ADVENTURE
131
Sue Vaughan in front of her scoria-filled earthbag dome, which is covered with standard cement stucco.
Above:The upper section of the dome from the inside, showing the geodesic structure.
SUE
VAUGHAN'S
HOUS E,
COLOR ADO
CA RO L
ESC OTT
AND
STEVE
KEMBL E'S
HOUSE ,
THE
BAHAM AS
Sue Vaughan wanted a very small, round house, so
Here is a house designed and built in the Bahamas by Carol Escott and Steve Kemble of
with the advice of Kelly Hart, she and two helpers
Sustainable Systems Support. The first phase of the construction, which consisted of the
built this 14 -foot (4 .2 meters) diameter, shallow dome with a sleeping loft made of scoria-filled bags. A concrete bo nd beam at the height of the door lintel supports a geodesic structure form ing the upper part of the dome.
structural earthbag walls, was constructed with the expert help of Kaki Hunter and Doni Kiffmeyer, who have developed site-built hand tools and a process for building that sim plified an d "neatened" this very labor -intensive cons tructio n met hod. Kaki and Doni's Honey House is described on page 140. This is a hybrid design where the first story is constru cted out of bags filled with native soil, upon which sits a second floor and roof constructed out of conventional timber frame. The second-floor joists are fixed to a reinforced concrete bon d beam on top of the earthbag wall. The house was built on a small island very close to the beach. Th e fill for the earthbags
Section of Sue Vaughan's dome.
was locally available sand dredged from the sea, which was very fine and contained a high propo rtio n of crushed coral, so it was very easy to compact. When slightly moistened and tamped, the bags turned to solid blocks.
The finished house. Preparing the foundation.
132
Since the ground around the house was sand, drainage was not a problem; there
133
ent. The most abundant and easily gath
to encourage biodiversity and habitat for
ered natural building resource is sand.
beneficial wildlife, as well as for privacy
fore, the foundation was very shallow with
Carol and Steve realized that where dredg
no gravel trench below, simply one row of
ing had occurred for a marina there were
To collect the breezes, Steve designed
piles of sand mixed wi th crushed coral,
the home to be two stories with an at
sand-filled bags below ground level.
around the house.
In an article in Earth Quarterly (see the
available free for the taking. When slightly
tached deck on the second level. The roof
bibliography), Carol and Steve describe
dampened and well tamped, the lime in
is hipped to shed heavy hurricane winds.
the premise of their design process: "Faced
the coral acts as a natural binder with the
The first level has walls made of sand- and
with the challenge of building on a remote
sand, which sets into a hard block.
crushed-coral-filled polypropylene bags
island in the Bahamas, we realized that...
Since the climate is subtropical, h ot and
along the perimeter, with a peaked, 8-
current construction trends in this part of
humid, ocean breezes are needed for com
point-ar ch opening in each of the six sides.
the world rely on the importation of al
fort. Most people clear-cut the bush to al
These arch openings have been left open
most all building materials in even the re
low the breeze to blow through and to
for breezes, and the covered lower level is
motest of locations. In keeping with our
eliminate hiding places for the mosqui
used for utility, storage, and a workshop.
work in the States, we want ed. .. to use this
toes, but Carol and Steve let the foliage
At the center of the lower level is a 3,000-
project as a demonstr ation of appropriat e
grow around their site in order to provide
gallon, concrete-block rainwater cistern,
earth building techniques . . . in hope of
overstory protection for new plantings,
which also serves as a load-bearing sup
influencing a shift in... building/develop
shade to help with moisture retention, and
port for the second level.
ment needs." First floor under construction.
Carol and Steve faced serious difficul ties: The Bahamas are subject to devastat ing hurricanes each summer and fall.
line of roof overhang
wall plate anchor bolted to bond beam
resulting in a 2 0 -inch-wide (50 -centime
reinforced concrete bond beam
ter) wall. The next four feet were built with
reinforcement rod pins
wide (35 centimeter) wall. Since the earth-
There are voracious termites, making any wood product is subject to attack. It also
continuous tubing, resulting in a 14-inch-
rains frequently and things may stay moist
bag walls were made very smooth with a
four-point barbed wire
for weeks. The intense summer sun can cause even pressure-treated wood, if ex posed, to deteriorate in as little time as five years. According to Carol and Steve, the Baha
These earthbag walls used misprinted
50 -pound rice sacks for the first four feet,
high-precision finish, there was no rough straps over the bond beam reinforcement rods
texture to permit the stucco to be effec tively keyed into the wall surface, which to reinforce the cement render was therefore
well-compacted bags filled with local sand
covered with a layer of chicken wire, se
mas have developed very little industry
cured to the walls with galvanized tie-
except for tourism, so most building ma
wires laid between bag courses as the walls
terials are imported from the United States. In terms of native resources, the
were built. The bond beam was strapped to the earthbag wall using both th e chicken
compacted sand
majority of vegetation is low bushes, with trees for lumber being virtually nonexist
wire and the poly strapping, which was ratchet tightened before stuccoing.
Plan of ground floor. Plan of ground floor, used as utility area and workshop.
134
THE
EARTHBAG
ADVENTURE
135
The 51 2 square feet ( 40 square meters) of the ground floor, earthbag stage of the house took three months to build, requir ing 50 0 bags and a 1,400 -foot roll of
polyp ropy lene tubi ng. Carol and Steve conclude: "After the completion of Phase 1 (the earthbag wall base) we were very pleas ed with th e resul ts of the project. The islanders have accepted it, stating that it looks like the old 'rubble stone' ruin s arou nd the island. It feels very stu rdy ... enough to take the worst hurri cane, relentless sun, and regular wind blown r ains . It cost a fract ion of the m oney any other option woul d have, to get to this poin t. Alt hough it to ok a lo t of ma nual la bor, i t is a doab le m eth od wit h onl y min i mal hand tools, and we had fun coordinat ing our team work into a smooth process. The three young men we trained are look ing at building houses for themselves us
K ELLY AND R O S A N A H A R T ' S H O U S E , C O L O R A D O
ing this method, and are even discussing
This house, designed and built by Kelly
beco ming contr actor s for o ther people. "
Top: Ground floor during construction. Bottom: Earthbag stairs.
wall covered with papercrete inside and
and Rosanna Hart of Hartworks, Inc., is in
out will have an R-value as high as 4 0 ,
a small town at 8 , 0 0 0 feet in the foothills of
which is higher than building codes re
the Sangre de Cristo Mountains of south
quire. Scoria is also light and fast to work
ern Colorado. Several interesting features
with.
distinguish the main dome of this house.
Another unusual aspect of this house is
The walls are constructed of bags that
that although the main structural form
contain scoria, a very porous, pumicelike
appears to be a dome, it is not a self-sup
volcanic stone. It is locally available, and
por tin g corbele d dom e. For a tru e cor
like pumice, it has many air pockets and so
beled do me, th e design nee ds to be cir cular
is very light. Due to its porosity, scoria is a
in order to create an evenly curved wall
good insulator and also provides thermal
upon which the vertical and horizontal
mass, so the house can absorb the sun's
forces are equal everywhere. In this case,
heat and retain it throughout the night.
the plan is oval, so t imber poles have been
Kelly estimates that the finished scoria bag
used as a type of pitched-roof teepee ar-
Roof structure to support the scoriafilled bags.
136
THE
EARTHBAG
ADVENTURE
rangement, insulated with scoria-filled
below g rou nd level. Then 6 to 8 in ches of
(500 millimeters) wid e, making sure the sand is dam p when filling
bags partia lly s uppo rted by th e pol es.
loose scoria was put over the entire build
the bags, well tamped and buttressed.] So we switched to scoria,
This dom e is also covered with a differ
ing area to serve as insulation and good
which is a much lighter material and will pack into a tight, stable
ent type of plaster, which is water resistant
drainage. There is no other foundation or
wall. Because of the lightness of the scoria, in addition to the usual
and insulative: a mixture of paper and ce
drainage, since the soil is pure, fine sand.
four-point barbed wire running between each course of bags, we
ment or lime, or a combi nation of the two,
We tried using the on-site dry sand to fill
tied the bags to each other with poly baling twine [see photo on
often called "papercrete" or fibrous cement.
our polypropylene bags (misprinted rice
page 54] , which provides a mat rix of fabric across the entire wall to resist fragmenting. It also gives the finish plaster something to
The house is a hybrid, a juxtaposi tion of
bags) , but s oon dis covered th at at a c ertai n
different materials, as well as a net work of
poin t after about five feet of stack ing, the
grab on to (especially importa nt on interior walls, where in domes
interconnecting structures allowing the
bags wo uld n ot h old th eir s hape a nd wit h
you are working against gravity).
area of the house to be quite large without
out buttressing the wall would collapse.
"We used individual bags as building blocks, rather than using
using one single dome.
[Author's note: When building with very
long tubes of material, because the s mall bags are easy for one per son to carry, and when we tried putting the scoria in long tubes,
Kelly Hart describes part of the con
sandy soils, which consist of round par
struction process: "The sloping site was
ticles of sand, a test structure should be
leveled and dug down about a foot below
built pri or to cons truc tion of the main
the eventual floor level, which was 5 feet
house, with bags not less than 2 0 inches
With an old woodstove in the foreground, the dining area under the loft can be seen beyond. Flagstones are set in adobe in the foyer. Beyond the table is a windowseat constructed with earthbags.
Plan of ground floor.
137
138
THE
EARTHBAG
ADVENTURE
139
there was a tendency for the whole thing to roll off the wall. [Author's note: This was due to the fact that the tube was narrow and scoria cannot be made compact in the same way that slightly damp earth or sand can. Therefore it may be advisable not to fill the tu be completely bu t loosely, to allow for tamping. Also, always carry the fill to the bag, eli minating the need to lift.] With the i n dividual bags, the bottom seam provides a distinct flat orientation that resists rolling. "Bags were stacked over a wooden form for the arched door ways. We used a plastic pipe to make air vents. Many of the win Kelly applying
dows were created using old wagon wheels or culvert couplers to
papercrete to the
hold the circular shape, and since most of the windows are not
outside of the dome. This doorway has a
operable, the glass used was often unclaimed or cut to the wrong
span of 6 feet made
size; these thermal panes can be fou nd cheaply at glass shops. They
possible using the
were imbedded directly in the papercrete (which is so dimensi on-
double-bag, crosshatch method of scoria arch.
ally stable it will not break the glass), and a second, final coat of paper crete with sand w as ap plied to t he outs ide, overla pping the glass. "The space connecting the two domes is framed with wood on the south side, while the nor th side is an insulating scoria-bag wall in the shape of a semicircle. Because of the expanse of glass in this greenhouse section, a nd the need for a flat place to mou nt the solar
Kelly explains, "With the pantry dome open, you can
water panels and PV modules, I chose to use conventional wood
see how the bags are stacked, those long rafters
framing on the south. The north side of the house is bermed with
helping to support the bags. Because of the relatively shallow pitch, bermed with earth on the
about four feet of earth, and a moun d of earth covers the pantry in
Unbuttressed arch.To create an arch spanning more
outside, and the considerable weight it would bear, I
the north.
than 3 feet using lightweight scoria bags, Kelly
decided to use logs. Before the pantry was backfilled with sand, I put on two layers of 6-mil plastic sheeting. The dome has not leaked and stays around 40 to 50 degrees Fahrenheit."
"The final layer on top of the papercrete is lime-silica, sand, and white Portland cement plaster. "Because of the elliptical shape, this dome is not as inherently stable as it would be if it were circular, which is why I used the timber pole. The forces are not uniform, so I had to struggle to keep the shape I wanted. I would not recommend that anyone re peat t his expe rimen t, t hou gh I do love the shape and feeling as it has turned out." Kelly has made a video of this cons truction process (see the re sources list).
devised the crosshatched, double-bag arch system shown here.
140
THE
EARTHBAG
141
ADVENTURE
bags per person per hour, so a team of four
then backfilled with gravel and earth. The
averaged sixteen bags per hour, and abou t
interior walls are earth plastered with local
ninety-six bags in a 6-hour day. The
white clay and milk-based alis paint. The
Honey House is made of eight hundred
earthen floor is poured adobe over 4
bags overall. The whole structure took just
inches (100 millimeters) of gravel and
nineteen days to complete. The earthen plaster was made with 7
stone with mud mortar, sealed with a natural, oil-based floor finish.
tons of cob, which took seven days to apply
Except for utilities, windows, and
all the way up to the roof, which has a 6-
doors, t he cost of this house was $1,020,
inch base for a "live cob thatch roof," where
which was the cost of the bags (a quarter of
living grass roots were mixed into the final
the final cost, including delivery), home
layer of roof plaster.
made tools, plywood arch forms (which are reusable), chicken wire, backhoe rental, twenty bales of straw for the earthen plaster, two rolls of barbed wire, and the 40 tons of sand, delivered.
In their manual Earthbag Construction (see the bibliography), Kaki and Doni have described their method this way, "We have adopted the FQSS stamp approval—Fun, Quick, Simple, and Solid. By following this The Honey House with
criterion, we have made the ease of the con-
sculpted gutters and grass seeded in the
KAK I
HU NT ER
AND
DO NI
KIFFMEYER'S
HONE Y
HOU SE,
First floor under construction.
final layer of earthen plaster.
struction process our priorit y. As long as the
UTAH
This house was designed and built in
down buttresses, and away from the foun
Moab, Utah, by Kaki Hunter and Doni
dation.
Kiffmeyer of the pioneering firm OK OK
No cement was used in this structure!
OK Productions, who have elevated earth-
The bags used were small "misprint"
bag constr uction to a precision craft. The
bags of two sizes: 17 inches wide by 30
structure is a corbeled earthbag dome with
inches long and 22 inches wide by 36
a 12-foot (3.6 meter) interior diameter.
inches long. The fill material used was "re
Forty tons of earth were needed to fill the
ject" sand from a local gravel yard. This
bags, and 9 more tons were used for
had the ideal ratio of 25 percent clay to 75
sculpted adobe and for a "living thatch"
percent sand for rammed earth co nstruc
roof. The gutter system is sculpted adobe,
tion. The time taken for filling and tamp
which steers the water around windows,
ing the bags averaged four of the smaller
work is Fun and Simple, it goes Quickly and the results are Solid. When the work
The interior has a sunken floor, 2 feet
becomes in any way awkward, FQSS de
(60 centimeters) deep. The earthb ag wall
teriorates into Frustrating, Quarrelsome,
starts at this level; there is no concrete
Slow, and Stupid, prompting us to stop,
foundation. Plastic bags were wrapped
change tactics, or blow the whole thing off
around the exterior of bags below grade
and have lunch (returning refreshed often
for waterproofing from ground moisture,
spontaneously restores FQSS approval)."
142
THE EARTHBAG ADVENTURE
THE
L ODGE
TH E
"NJAYA," MAL AWI
NE W
HO US E
OF
143
THE YAQU IS,
ME XI CO
the village, and no sanitation facilities
In structures like the bathing room in the backpackers' lodge "Njaya" in Malawi, in s outheast
The indigenous Yaqui community of
Africa, Adrian Bunting experimented with the sandbag technology prior to constructing
Pueblo de Sarmiento is located on the out
apart from an outho use. In spite of the low
a larger sandbag project—an eco-lodge in southern Tanzania. As Adrian explains, "I was
skirts of the city of Hermosillo, capital of
standard of living, we remarked upon a
trying to get the ha ng of the sandbag technology based on a couple of photos on the Web.
the Mexican state of Sonora, which bor
sense of cheerfulness all around.
The beach in Tanzania is as remote as you can probably get, so the plan was to build as
ders the United States. Mexico's govern
much as possible with the available materials, basically sand and coconut trees. In Africa,
ment gave a ten-acre parcel of undevel
on-site, we saw that one of the
concrete is what everybody wants to build with, bu t a lot of this is done with lime obtained
oped land to the Yaquis of Hermosillo in
few resources that was abun
from live coral reefs, sustaining huge damage. It's also very expensive. I was sent to Malawi to
1995. This land is a desert at the bottom of
dant was earth—very sandy
see if the sandbag technology was a viable option for constr ucting chalets in Tanzania. As
the surrounding hills.
with hardly any clay—so the
far as I could see, it was worth trying if only to achieve the thermal insul ation these build
Giovani Panza, of the organization
ings provide, and also the ease of sealing against mosquitoes, since any timber b uilding is
Itom Yoemia Vetchivo, whose mission is to
impossible to make bug-free." The construction procedure used in Malawi is very different from the method de
Taking stock of the materials available
earthbag technology would be very appropriate.
find funding for projects that improve the
The house was to be a Nader
Yaqui community's living conditions, be
Khalili-designed, low-cost pro
scribed in this book. As Adrian explains, "The bags are filled with pure dr y lake sand, of a
came acquainted with Pueblo de Sarmi
totype, the "three-vault house,"
granite type. There is no barbed wire, and I did find the bags slipped during construction
ento through a conference of indigenous
which utilizes a simple design
so the roof has reinforcement bars bent and used as a permanent form. The corr idor is just
people s of th e Mex ico-U .S. b order , whi ch
based on th e re petit ion o f single
stacked in an arch.
was held in Hermosillo. In the spring of
arched units, simplifying con
"You might be interested in a conversation I had with the builder when we started the
1997, Itom Yoemia Vetchivo received a
struction. Khalili's arrangement
roof. He was shaking his head, so I asked him why. He replied that this wasn't a roof. I asked
grant of four thousand dollars to build the
of vaults eliminates the need for
him why, and he replied, 'A roof is made of tin.' I
Yaqui community a prototype low-cost
corridors, and additional vaults
said, but tin is noisy when it rains, it
shelter, and they approached Cal-Earth
can be added later easily. Resi
for help. With two volunteers experienced
dents have a view through the
in conventional construction who were
depth of two vaults at one tim e,
carrying out apprenticeships at Cal-Earth,
increasing the sense of interior
plied. But this is ten times
I offered to coordinate this project, which
spaciousness, and variety can be
cheaper, I pointed out.
was organized as a three-week volunteer
introduced through placement
'I see,' he said.. .."
project .
of windows and other elements
heats up quickly in the sun, and
bent reinforcement rods (rebar) forming a dome shape
when it's old mosquitoes get in. 'It is still a roof,' he re
earthbags stacked flat without barbed wire
The people of Pueblo de Sarmiento
such as niches and alcoves. A Top: A house con
usually build their own homes out of
wind catcher faces prevailing summer
whatever is on hand: cardboard, corru
breezes to direct air into the hous e for
gated asphalt sheeting, and s mall pieces of
cooling. In addition, the vaulted curve of
unbearably hot in the
The permanent, dome-
found timber. These structures need to be
the roof creates sh aded zones of cooler air,
Mexican sun.
shaped structure used
rebuilt after the seasonal hard rains. They
while the sun's path overhead encourages
to support the
had one source of fresh water coming into
air movement inside house by gradually
sandbags.
structed of corrugated asphalt, which becomes
Above: Prototype of the three-vault house.
THE
144
shifting the shaded zone up and over the
merriment, they embarked on this adven
vault.
ture with space-age technology. Their first
Contrary to my intentions, the people
day of laying bags was very slow, but soon
of Sarmiento were asked to prepare a con
they gained experience and speed. The
crete foundation prior to our arrival,
Cal-Earth advisers, who were not them
which was the first of many unnecessary
selves accustomed to alternative construc
measures in this project. Due to this extra
tion, had insisted on putting 12 percent ce
work, time was lost.
ment into the earthen fill, thereby treating
A team of fifteen Yaqui workers had as
the bags as concrete forms instead of
sembled for the project. Some were from
ramme d earth. In six days, the laying of the
this community, and others came from the
earthbags was complete and the structure
village of Ciudad Obregon, farther south.
was ready for the vault construction. Over
They were all to receive standa rd Mexican
the whole week, the speed of the bag laying
wages, which to us meant that their motive
averaged 23 feet per hour per team, with
for working hard would not be primarily
three people in each team.
EARTHBAG
ADVENTURE
145
educational. Yet with all this available la
At this stage, we faced a huge di
is the point of building a house without
the roof structure; and rigid foam, for the
bor, I could not have f oreseen w hat could
lemma—whether to build some kind of
any wood if you are going to use vast
insulation. There were numerous possible
go wrong.
timber formwor k (the cost of which would
amounts of wood for the formwork?" was
alternatives. For instance, the foundations
Once the concrete of the footings had
come to more than what was budgeted for
the commonsense question. A way of
could have been inexpensive gravel- or
cured, the work began. At first, earthbag
the whole house), or instead to try and
buil ding a vault usin g rein force ment rods ,
rubble-filled trenches; or two stabilized
construction seemed very strange to the
devise a way of constructing the vault us
expanded metal mesh, and rigid foam in
earthbag rows laid directly on undisturbed
Yaquis, and reluctantly, but with great
ing permanent, built-in formwork. "What
sulation was devised. "What happened to
ground, since this is not an earthquake
the idea of natural, alternative construc
area; or two courses of bags filled with
tion?" was my constant question.
gravel laid on undistur bed ground (see the
Unfortunately, the concept of empow erment through use of the simplest tech
descriptions of earthbag foundations in
chapter 3 ) .
niques and the most available materials
There was no need to put any cement in
was almost lost, because the local people
the fill for the walls. The earthba g technol
were unable to build more of these build
ogy has been specifically developed for
ings due to the vast cost of the materials
buil ding in areas wit h no clay or wood, an d
used in the prototype. So what went
using unstabilized earth would have been
wrong? Why did the project's cost escalate
entirely practical at Sarmiento. For the
from the four thousand budgeted to ten
roof structure, it would have been better to
thousand dollars? The most expensive
use the locally grown, bamboo-like carrizo
material costs of the project were: cement,
reed for vaults (see page 6 7 ) , or corrugated
for foundations, walls, and roof; metal, for
metal sheeting, which is cheap and easily
THE
146
EARTHBAG
ADVENTURE
available. As for insulation, a straw-clay
ways was a success. The Yaqui workers
mix would have been preferable to expen
from Hermosillo had never worked so
sive rigid foam (see the discussion of roofs
closely with Yaquis from other areas, nor
in chapter 5).
with foreigners. The process was truly a
This project underscored the truth that
tinuous
technique is necessary to avoid unneces
laughter. Everybody was learning one or
sary cost and complexity. Moreover, when
and resilient. Above: Expomat mesh fixed under the reinforcement rods to form a rough surface for the soil-cement coating layered on top. Right: View from vault 1 of the proposed entrance area and the intersection of vaults 1 and 2.
problem-solving
and
endless
two of the languages that were being spo
working with builde rs who speak different
ken at all times. Yaquis were actively in
languages, it is important to acquire the
volved in the formulation of the budget
basics o f the local p eople' s langu age i n or
and the purchase of the materials (Kari
der to work effectively. Unless your trans
1997). Ultimately, the "New House of the
lator has extensive knowledge of the build
Yaquis" was truly a surprise to everybody.
ing process, it will be difficult to have any
It was built by the concentrated labor of
in-depth communication.
the whole communi ty, and because the ef
several big mistakes, the project in many
fixed in their arched shape, the structure is strong
communal experience, marked by con
a thorough understanding of any building
Yet in spite of our feeling that we made
Top, and top, right: When the reinforcement rods are
147
fort was demanding of everyone, it left a deep impression on every person involved.
BIBLIOGRAPHY
AFTERWORD
Andreson, Frank. "Oh Muddy Clay, O Clayish Loam: Introduction to German Clay Building
To live in a natural hous e is a privilege. Through the process of natural building, we can reconnect with the basics. We can find simple solutions to seemingly complex prob lems , often allowing nat ure inste ad of ma chin ery to do the work. We can create communiti es that reconnect us with the earth and with each other, for earth itself is the most wonderful mate rial, feeding us and housing us. And to possess knowledge of some of earth's mysteries is a great gift, allowing enormous freedom. I hope that all those looking through the pages of this book draw inspiration to create their own home, and to adapt their house to its unique, individual, and distinctive environment. It's your game, it's your joy—go a nd play!
Techniques." Joiners Quarterly:
The Journal of Timber Framing and Traditional Building 37
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The Cob Builders Handbook: You Can Hand-Sculpt Your Own Home. Cottage Grove,
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The Cob Buildings of Devon 1 : History, Building Methods, and
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Engineering 2, no. 3 (1989).
Minke, Gemot.
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Rudofsky,
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The New Independent Home: People and Houses that Harvest the Sun, Wind, and
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W o o d w a r d , I . Nature's Little Builders. Thailand: Sirivanata Palace Press / Electric Paper, 1995. Zelov, Chris, and Brian Danitz.
Ecological Design: Inventing the Future. Video recording. Ecological
Design Project, 1996. Distributed by Chelsea Green. Ziesemann, Gerd, Martin Krampfer, and Heinz Knieriemen. Naturliche Farben: Anstrkhe und Verputze selber herstellen. Aarau, Switzerland: AT Verlag, 1996.
RESO URCE S
PERIOD ICALS
Adobe Builder. Southwest Solar adobe School, PO Box 153, Bosque NM 87006 USA. Telephone: +(505) 861-1255. Internet: www.adobebuilder.com . Adobe Journal. Published by Michael Moquin, PO Box 7725, Albuquerque NM. 87194 USA. Telephone: +(505) 243-7801. Building f or a Future. The Association for Environment-Conscious Builders. Nant-y Garreg, Saron, Llandysul, Carmarthenshire, SA 44 5EJ England. Telephone: +01559 370908. Building with Nature. PO Box 4417, Santa Rosa CA 95402. USA. Telephone: +(707) 579-2201. Designer/Builder. 2405 Maclovia Lane, Santa Fe NM 87505 USA. Telephone: +(505) 471- 4549. Earth Quarterly. Box. 23, Radium Springs NM 88054 USA. Telepho ne: +(505) 526-185 3. Eco Building Times. Northwest Eco Building Guild, 217 Ninth Ave., North Seattle WA 98109 USA. Eco Design. PO Box 3981, Main Post Office, Vancouver BC V6B 3Z4 Canada. Environmental Building News. 122 Birge Street, Suite 30, Brattleboro VT 05301 USA.
Telephone:
+(802) 257-7300, internet: www.ebuild.com . Erosion Control:
The Journal for Erosion and Sediment Control Professionals. Published m onthl y by
Forester Communications, Inc., 5638 Hollister #301, Santa Barbara CA 93117 USA. Telephone: +(805) 681-1300. Green Building Digest. Queens University of Belfast, 2-4 Lennoxvale, Belfast BT9 5BY Northern Ireland. Telephone: +01232 335466. Green Connections. PO Box 793, Castlemaine 3450 Australia. Telephone: +(03) 5470 5040. Home P ower. The Hand s-o n Journal of Home-Made Power. PO Box 14230, Scottsdale AZ 852674230 USA. Telephone: +(919) 475-0830. Joiners Quarterly.
The Journal of Timber Framing and Traditional Building.
PO Box 249, Brownfield ME 04010 USA. Telephone: +(207) 935-3720. Permaculture. Permanent Publications, The Sustainability Centre, East Meon, Hampshire GU32 1HR, England. Telephone: 01730 823311, internet: www.permaculture.co.uk . Positive News. The Six Bells, Bishops Castle, Shropshire SY9 5 AA. England. Telephone: + 01588 630 121/122. The Last Straw: T he Grassroots J ourn al of Straw Bale and Natural Building. HC 66, Box 119, Hillsboro NM. 88042 USA. Telephone: +(505) 895-5400. e-mail: [email protected], internet: www.strawhomess.com .
153
RESOURCES
154
The Permaculture Activist. PO Box 1209, Black Mountain NC 28711 USA Telephone: + (828) 298-
155
The Cob Cottage Company Workshops and resources in cob construction and passive solar design.
2812.
PO Box 123, Cottage Grove, OR 97424 USA. Telephone: +(541) 942-2005, internet: ORGA NIZAT IONS
AND
COMP ANIE S
IN THE
U.S.
AND
THE
U.K.
Frank Andresen Construction with light clays and clay plasters; also offers dry clay products as well as workshops and
www.deatech.com/cobcottage Construction Resources
consulting.
Kiefernstrasse 2, 4000 Dusseldorf, Germany. Telephone: +0211 7333216. Kevin Beale.
Specializing in ecological construction techniques. Exhibition center, resources,
lectures.
16 Great Guildford Street, London SE1 OHS UK. Telephone: +020 7450 2211. Constructive I ndividuals Architects specialising in
alternative construction,
self-build projects,
and construction
workshops.
London, UK. Telephone: +020 7515 9299.
Design, consultation, and construction using earthbag, straw bale,
and other methods.
Ty-Capel-Graig , Talsarnau, Gwynedd, Wales. LL47 6UG, England. Telephone: +(0) 1766 770 696, e-mail: [email protected].
CRG Design Healthy Homes
Black Range Lodge Videos, educational materials, and resources for straw bale, cob, techniques.
Bed &
and other alternative building
breakfast lodging for educational retreats.
Star Route 2, Box 119, Kingston NM 88042 USA. Telephone: +(505) 895-5652, internet:
e-mail:
Design and
consultation services.
[email protected].
Building code information
Building Biology and Ecology Institute of New Zealand 22 Customs Street West, PO Box 2764 CPO, Auckland, New Zealand. Telephone: +(64-9) 358 2202.
Founded by Iranian Architect Nader Khalili to pursue research in sustainable human shelter earthen materials and an earthbag technique called "Superadobe" for domes
and vaulted structures. Apprenticeship retreats,
and educational resources.
David Eisenberg, PO Box 27513, Tucson AZ 85726 USA. Telephone: +(520) 624-6628, e-mail: [email protected], internet: www.dcat.net. Earth Hands & Houses, and PWA Architects
California Institute of Earth Art and Architecture ( Cal Earth)
and weekend visitations to the demonstration site.
Cal-Earth , 10225 Baldy Lane, Hesperia CA. 92345. USA. Telephone: +(1) 760 244 0614, e-mail: [email protected], internet: www.Calearth.org.
Design, consultation, workshops and construction of sustainable,
ecological,
'organic' projects
in
developed and developing countries. Paulina Wojciechowska, Architect. 18 The Willows, Byfleet, Surrey KT 14 7QY England. Telephone: + (0) 1932 352129, e-mail: [email protected], internet: www.EarthHan.dsAndHouses.org. Earthwood Building School
Canelo Project Set up by the co-authors of The Straw Bale House. Offering comprehensive straw bale construction workshops and educational resources,
with a focus on
practices including earthen plasters, floors, and bread ovens.
traditional materials and
Workshops in southern Arizona and
Mexico. HC1, Box 324, Elgin, Arizona 85611 USA. Telephone: +(520) 455-5548, e-mail: [email protected], internet: www.caneloproject.com
Workshops and educational resources, living
Resources,
workshops,
mortgage-free living,
and design
consultations for cordwood-masonry construction, stone circles,
and off-the-grid energy strategies.
Rob and Jaki Roy, 366 Murtagh Hill Road, West Chazy NY 12992 USA. Telephone: +(518) 4937744. Gourmet Adobe Specializing in clay slips with mica and adobe. Carole Crews, HC 78, Box 9811, Ranchos de Taos, NM 87557 USA
Centre for Alternative Technology sustainable
Supplier of natural building materials.
Cedar Rose, PO Box 113, Carbondale CO 81623 USA. Telephone: +(970) 963-0437,
Development Centr e for Appropriate Technology
www.epsea.org/straw.html
principally through
CRATerre-EAG School of Earth Construction Maison Leurat, Rue du Lac, BP 53, F-38092, Villefontaine Cedex, France.
with a
large bookshop for alternative construction and
information.
Hartworks, Inc. Producers of a two-hour video (see the Bibliography) available in
U.S. standard NTSC VHS
Machynlleth, Powys SY20 9AZ, Wales, UK. Telephone: +01654 702400, e-mail: [email protected],
format. Includes a section on earthbags, as well as covering other natural building techniques.
internet
Another video specifically on
http://www.cat.org.uk
earthbag construction is in production.
Kelly and Rosana Hart, Hartworks, Inc., PO Box 632, Crestone, CO 81131, USA. Telephone: +(719) 256 4278, e-mail: [email protected], internet: www.hartworks.com .
156
RESOURCES
157
Heartwood School Johnson Hill Road, Washington MA 01235 USA. Telephone: +(413) 623-6677. EQUI PMEN T
Willbheart@aol. com
Dominic Howes, other
alternative
AND
SUPPLIES
Continuous berm machine for filling earthbags
Imagination Works builder and consultant of alternative
home construction
using earthbags and
Can extrude a continuous berm at r ates of 10 to 50 feet per minute. "No trenching or stacking required.
methods.
With weight typically exceeding 100 pounds per foot,
the continuous berm
conforms
RO. Box 477, Dragoon, AZ 85609 USA. E-mail: [email protected], internet:
tightly to underlying soil surfaces, will not blow over, and is extremely difficult to dislodge from
www.sfhet.net/imagination.
original placement location. Additionally the berm bank stabilization,
Intermediate Technology Centre
(description from Erosion
Bookshop and educational resources.
0378 USA. Telephone: +(414) 644-5234.
International Institute for Bau-Biologie & Ecology.
Aur o Pro duct s
PO Box 387, Clearwater, F L 33757 USA. Telephone: +(813) 461-4371, e-mail:
For casein, natural paints,
bau bio log ie@ ear thl ink .ne t, int er net : www .ba u-b iol ogi eus aa. com
writer,
and peripatetic scholar of natural building and ecological design.
internet: www.dcn.davis.ca.us/go/sinan/auroinfo.html or www.auro.de/
Livos Phytochemistry of America
Teaches, gives workshops and consultations.
Natural,
Star Route 2, Box 119, Kingston, NM 88042 USA. Telephone: +(505) 895 5652, e-mail:
nontoxic paints and stains.
13 Steeple Street. PO Box 1740, Mashpee MA 02649, USA.
[email protected].
Tel: 508 477 7955. www.livos.com for natural paints and wood finishes.
OK OK OK Productions Providing earthbag construction, training, along with workshops on wild clay and lime plasters, consultations for dome and
259-8378, e-mail: [email protected].
Out on Bale by Mail (un)Ltd. Straw bale consultation,
educational programs, wall raising supervision, and bulk orders
of the
book Build It With Bales (s ee the bibliography). 2509 N. Campbell, #292, Tucson, AZ 85719 USA.
Sustainable Systems Support consultation, workshops.
Specializing in earthbag and straw bale construction methods.
Source of printed and video resources. Carol Escott and Steve Kemble, PO Box 318, Bisbee, AZ 85603 USA. Telephone: +(520) 4324292, e-mail: sssalive@primene t.com, internet: www.bis beenet .com/b uildna tural/ .
Wom en Bui ld Hou ses Workshops, referrals, and tool library. 1050 S. Verdugo, Tucson AZ 85745 USA. Telephone: +(520) 882-0985, e-mail: [email protected] .
Livos UK Unit 7 Maws Croft Centre, Jackfield, Ironbridge, TF8 7LS UK. Telephone: +0 1952 883288
arch construction.
Kaki Hunter & Doni Kiffmeyer, 256 East 100 South, Moab UT 84532 USA. Telephone: +(435)
Design,
oil solvents, waxes, and other finishes.
Sian Company, PO Box 857, Davis, CA 95617-3104 USA. Telephone: +(916) 753-3104,
Joseph Kennedy
earthen floors. Design
or used separately for check structures."
Control journal.)
Available from Innovative Technologies, PO Box 378, 250 Hartford Road, Slinger, WI 53086-
103-105 Southampton Row, London WC1B 4HH, UK. Telephone +020 7436 2013.
Architectural designer,
can be cut into sections and stacked for stream-
'sand bagging,' fluids containment,
INDEX
INDEX
159
finishes, 76, 83, 90, 97
finish stabilizers, use of, 79
materials for, 13, 38, 43-45
furniture, 114, 115
roofs for, 65, 71, 80
recycled bags, 44, 45
soil mix, 17, 46, 103, 107-108 thatched roofs, 68-70
Devon Earth Building Association, 97
cold climates
Devon Historic Building Trust, 108
earthen plasters, effect on, 77
bees wax, 119- 20
cement
butt res sing , 26, 44, 5 4-5 7, 136
connecting, 13, 24-25, 136, 139
insulation for, 111
compass for, 34, 48-49
lime plasters, application of, 87
corbeled, 27, 49, 110, 135, 140-41
soil mix for, 106
defined, 22, 26
in dry area, 35-37, 66
earthbags, construction using (See
examples, 123-47
compression rings, 46, 79
additives. See stabilizers
bin der s. See also clay
environmental impact, 46, 79, 89, 92
compass, construction, 34, 48-49
finish stabilizer, 46, 66, 75, 78-79,
compression rings, 26, 46, 54, 57, 79,
in limewash, 97
89-91, 100-101, 136
cracks allowed, 105
in paint, 95
earthbag foundation, 38
as sealant, 93
finishes, 76, 80, 90
soil mix using, 103, 105-109
stucco, 90, 123, 127 cement-stabilized earthbags, 37, 38, 46,
123, 125, 136 concrete. See also cement bo nd be ams , 18, 60 -6 3, 123, 127,
62, 89, 123, 144-45
130-34
finishes (See finishes) labor intensity of, 13
earthquake resistance of, 15
layout of, 13-14
examples, 123-26, 135-42
recycling, 17
form, use of, 49
seismic and structural testing, 14-15
openings [See openings)
shape of, 32-33 (See also domes)
Center for Appropriate Technology, 15
furniture, 114
bo nd be ams , 15, 18, 46, 60- 63, 66, 79 ,
Ceramic Houses (Khalili), 21-22, 26
connectors. See passageways
for roofs, 66
clay-based building materials, 5-6, 19,
Constructive Individuals, xiv
shell, determining thickness of, 27
corbeling, 16, 26-27, 43-44, 49, 110,
spanned, 22
123, 127, 130-34
soil mix, 17, 46, 103, 107 Africa, 6, 16, 18, 19, 22, 142 Ahlquist, Allegra, 56, 127 alis, 95-97, 114, 141 alkaline materials, 81, 83, 84, 106
Building Biology and Ecology Institute of New Zealand, 98 bui ldi ng co des, 4, 14, 90, 105 Bunting, Adrian, 142 bur lap bags
46. See also adobe; cob construc tion; straw-clay blends as binder, 6, 103, 105-109 bit ume n used with , 89 interior walls, floors, furniture, 103
135 tion for, 38 costs, 13
moisture control and, 76
Ahlquist square house, Arizona, 127
apses, 22, 26
for insulation, 110
soil analysis, 80, 103-105
of earthbag bags, 45
arches, xvi, 13, 21-24, 138-39. See also vaults for additions, 17 butt res ses for, 2 3- 24, 57, 60
butt res ses . See also tension rings
clay finishes
for arches, 23-24, 57, 60
erosion of, 77
domes, 26, 44, 54-57, 126, 136
interior plaster, 92
dry area, construction in, 35
as sealant, 93
sand-filled earthbags, 49, 136
waterproofing, use for, 88-89
corbeled, 26
spring line, 23, 26
clay in earthbags, 13, 17, 18, 49
keystone, 23, 24, 59-60
straight walls, 127
cement stabilization of, 89
lancet (catenary), 22-23, 44
damp areas, construction in, 35-38,
unbuttressed, 139 Australia, 10 B
bags . See earthbag bags Bahamas, 16, 131-34
C
49
California, 14-15, 24, 34, 105
lime stabilizer use and, 83
California Institute of Earth Art and
poly pro pyle ne ear thba gs, use of, 75
Architecture (Cal-Earth), xiv-
clay slip, 95-97, 114, 141
xviii, 14, 43, 124
Cobber's Companion, The (Smith), 70,
Canelo Project, Mexico, 71-72, 100, 116
ban ana leaf juic e, 81
casein, 82, 97-100
bar bed wire , 36, 46, 5 4, 58 , 137
catenary (lancet) arch, 22-23, 44
104 cob construction, 4, 5, 6, 8-9, 141 earthbag foundation, 16
stability, increasing, 49 doors. See openings
for earthbags, 18, 43-45, 76
Escott-Kemble house, the Bahamas, 134 Hunter-Kiffmeyer house, 141 Njaya backp acker s" lo dge, Mala wi, 142
D damp areas, construction in, 13, 35-40, 49, 66. See also flood-prone areas, building in; waterproof ing; water resistance finishes for, 75
13, 43-63. See also bond beams; butt res ses ; ear thba g fil l; tion; openings
earthen floor, 117
appropriate use of earthbags, 16-17
gabions, 30, 39-40
cutting into bag, 17
gutters, 140
forms, use of, 25, 49, 58-59, 144-46
dry areas, construction in, 35-37, 66
for furniture, 18, 114
dryboard, 109-10
keying, 36, 54, 137
dry-stone foundation, 40
materials, 44-46 simplicity of, 19
Yaquis vault house, Mexico, 145, 147 Crews, Carol, 82, 90, 95-96, 107
earthbag construction m ethods, xiv, 4,
foundations; hybrid construc
drainage, 30, 37, 38, 75, 136
Tassencourt dome, Arizona, 125 CRATerre, 10, 78-79, 81
Earthbag Construction (Hunter and Kiffmeyer), 141
thickness of shell, determining, 27
animal product stabilizers, 79, 82, 106 arched openings, 13, 14, 21, 22, 58-60
utilities, 32, 120-21, 139
on square structures, 27
cordwood masonry, earthbag founda
80
methods)
bit um en, 79, 89
foundations, 38, 127, 144-45
design considerations, 13, 17, 29-33,
earthbag construction
floors, 118-19 roofs, 66
domes; waterproofing
hybrid house for, 128-29
ben ton ite clay, 8 8-8 9
bit umi n, use of, 89
damp areas, construction in; additions, planning for, 17, 32-33
additions, building, 17, 32-33
casein as, 98-99, 100
domes, xvii, 13, 14, 15
sources of, 19, 44 earthbag buildings, 13-19. See also
bric k, 18
ben ches . See furniture
adobe, 4-8, 140
disaster-relief housing, 13, 16, 43
"seconds," 44, 45, 133, 140 small bags, 52, 137
finish stabilizers, use of, 79
acidic materials, 81, 83, 92, 106
bon d be ams , 46 , 7 9
Devon Earth Builders, 90, 106-107
Cob Cottage Company, 109 bui ldin g ori ent ati on for, 31- 32
A
design considerations, 13, 17, 29-33, 80
E
earth architecture, xiv, 3-19. See also
structural walls of conventional house, 128-29
specific building methods, e.g.
tamping, 52-54
adobe
tools, 13, 46-49
clay-based building materials, 5-6 history of, 3, 5, 6, 22 revival of, 4-5 earthbag bags cost, 45 making, 45
tying courses together, 49, 137 earthbag fill, 16-17, 49-50, 131, 140 cement-stabilized (See cementstabilized earthbags ) filling process, 45-46, 50-52, 137-39 pH of, 81
,
i6o
INDEX
earthbag fill, continued
extenders (fillers), 93, 95, 103, 105-109,
pro ced ure , 140
114. See also sand
flood-resistant, 30-31
Hart dome house, 135-39
casein paint on 99
functions of, 34-35
Howes conventional-style house,
making, 86-87
soil analysis, 80, 103
extensions, building, 17, 32-33
gabions, 30, 39-40
width of filled bag, 45
exterior finishes. See plasters
ground, connection to, 35
external features, 18, 30, 32
level plane provided by, 33, 47
Earth Building Association, 88
for non-earthbag buildings, 16, 33,
Earth Construction (CRATerre), 78-79, 81 earthen floors, 103, 107, 115-20
38
F fiber. See also straw; straw-clay blend
161
128-29
pozz olan ic addit ives to, 87- 88 I insulation, 142
making (slaking), 84-86
construction, 118-19
interior finish plaster, 92
site preparation for, 33-34
scoria as, 136
in lime plasters, 83-84
trench, 35-38
walls, 50, 110, 112-14, 139, 145
in soil mix, 11, 106-109
walls, attaching to, 38, 39
fiber composite board, 109-10
France, 9-10
maintenance, 119-20
fill. See earthbag fill
furniture, 18, 30, 32, 103, 114-15
repair, 120
fillers. See extenders (fillers)
finishes for, 75
sealants, 93, 117, 119-20
finishes. See also plasters; sealants;
soil mix for, 106-107
for upper story, 118
casein, 98-100
interior finishes, 92-100 interior partitions, 103, 109-10, 114-15
J jar test, 104- 105
earthen plasters, 66, 75-77, 80
K
floor, 93, 117, 119-20
gabions, 30, 39-40
kaolin, 5-6
advantages/disadvantages, 76-77
interior, 92-100
geodesic structure, 130
Kemble, Steve, 16, 131-34
application of, 77-78, 91-92
keying in, 76, 86, 87, 126, 133
glass, 139
Kennedy, Joseph R, 15, 16, 18
clay slip (alis) finish, 95-97, 114, 141
maintenance, 77, 91, 100-101, 109
glue, casein, 82, 97, 98-99
keying
for furniture, 114
pape rcr ete , 101
Gourmet Adobe, 82, 90, 96
interior finish use, 92
roof, 66, 73
gravel, 13, 30, 35-38, 46, 49, 50
maintenance, 77, 91, 100-101, 109
soil mix for, 106-107
Great Britain. See United Kingdom
nonstabilized, cement plaster on, 90
spray application of, 76, 92
Great Wall of China, 9
perm eabi lity, 76, 80, 90, 93
fire protection
Obregon project, Mexico, 25
linseed oil
off-the-grid, 32, 126
lime-wash additive, 97-98
bra nch es, 36, 54, 137 finishes, keying in, 76, 77, 86, 87, 126, 133
oil-based paints, 100
as sealant, 93, 117, 119
OK OK OK Productions, 16, 140
as stabilizer, 81, 89
openings, 26, 54, 57-60, 138-39. See also compression rings
living roofs, 65, 70-71, 140,141
arched, 13, 14, 21, 22, 58-60
love, role in designing of, xvii
forms used for, 58-59 in hot climates, 110, 126
M
Outram, Iliona, xiv, 14
finishes, 77, 91, 100-101, 109
ovens, 30, 75, 103, 114-15
Malawi, 142
greenhouse, 63
keystone, 23, 24, 59-60
lime/manure render, 88
earthen plasters, 76
Guatemala, 15
Khalili, Nader, xiv, 14, 15, 21-22, 26, 34,
manure/wheat flour/sand plaster, 82
insulation, 110
gypsum, 81, 82, 86, 92, 114
waterproofing, 66, 88-89
thatch, 70
earthquake resistance, 15, 38, 54-55, 62 seismic testing, 14-15 tire foundation, 39 Egypt, 6, 19, 22 electricity, 32, 120-21 emergency relief, earthbags used for, 13-16, 19, 43
31 , 38, 43, 49 floors
38, 43, 124, 143 Kiffmeyer, Doni, 16, 52, 131, 140-41
flood-prone areas, building in, 17, 30-
H Hartworks, Inc. (Kelly and Rosana Hart), 12, 16, 130, 135-39 Hermosillo project, 16, 25, 56, 143-47
landscaping, 30, 31, 32
earthen (See earthen floors)
Hesperia Museum/Nature Center, 14,
lime-based stabilizers, 38, 46, 78-79,
Bauen, 15 foundations, 15-16, 34-4 1, 75, 76
24, 34
81-83, 86
casein, 99-100
Canelo project, 71-72, 100, 116
clay slip (alis), 95-97, 114, 141
Hermosillo project, 16, 25, 56, 143—
limewash, 95, 97-98, 100
47 Obregon project, 25 Save the Children project, 108-109 mica, 92
oil-based, 100 pape rcr ete , 75, 135, 136, 13 8, 139 plas ter mix reci pe, 12 pro per tie s of, 11- 12, 101
Middle East, 9, 19, 22, 25, 32
as roof covering, 65, 66
lime from coral reefs, 142
mineral stabilizers, 79, 82-83, 106
par ape t-t ie w all b uttr ess es, 23
Howes, Dominic, 16, 125-29
Lime in Building: A Practical Guide
moisture
passa geway s, 2 4- 25, 136, 139
concrete, 127, 144-45
Hunter, Kaki, 16, 52, 131, 140-41
in damp areas, 35-40
hybrid construction
erosion, 3 1, 32, 75, 76, 77, 106
details, 36-37
Ahlquist square house, 127
Escott, Carol, 16, 131-34
in dry areas, 35-37
earth and straw bale, 112-14
alkalinity of, 83, 84
Europe, 9-10, 68. See also United
dry-stone, 40
Escott-Kemble house, 16, 131-34
application, 86, 87
earth-filled tire, 39
foundations, 16, 33, 38-41
capping earthen plasters, 46, 77, 80,
examples, 127, 132, 136, 144-45
greenhouse, 63
expomat mesh, 25, 145, 146
P pai nts , 94- 100
hot climates, 31-32, 126, 132-33, 142
environmental building, xiv, 3-4
Kingdom
Mexico
L lancet arch, 22-23, 44
alternative, 118-19,127 Forschungslabor fur Experimentelles
overhangs, 32, 75, 76, 80
manure
stabilizers (See stabilizers)
Earthmother Dwelling Retreat, xvi-xviii
square, 57, 58, 60 Othona Community Retreat, xiv
earthen floors, 119-20
sealants, 80, 92-94
earth-filled tires, 39, 111
oil, 81, 115, 117, 119. See also linseed oil
in oil-based paints, 100
maintenance
of earthbag walls with barbed wire/
O
limewash, 95, 97-98, 100
lintels, 18, 62 G
Nub ian vault , 26, 59
mixing with sand, 86, 87
stabilizers
Earthen Floors (Steen), 100, 119
natural building, xiii, 4 Njaya back pack ers ' lo dge, Mala wi, 142
gypsum added to, 92
heating in, 127 layers, 116-17
lime putty, 97
roof, 70, 72-73
in earthen plasters, 77-78
N nailer boards, 114-15
foundation, 37, 38
alternatives to, 118-19, 127
insulation in, 111, 116, 117
rubble or mortare d stone, 39
recipes for, 88 water resistance of, 75, 90
earthen floor, 110, 111, 116
pum ice- cre te, 40- 41
resistance to (See water resistance) montmorillonite, 5-6
per mea bili ty of, 82- 83, 90, 93
(Schofield), 87
bar rier , 30
connecting, 13
lime mortar recipe, 88
damage caused by, 90-91
passiv e s olar. See solar energy
lime plasters, 66, 83-88, 136, 139
earthbag fill, moisture content of, 46
pH , 8 1, 83, 84, 92, 106
earthbags, moisture wicked into, 17,
plas ters , 16, 19, 25, 126, 1 39. See also
92, 93, 100, 114
30 per mea bili ty/ eva por ati on of (See walls, breathability)
earthen plasters; lime plasters application of, 91-92 for burlap bag construction, 76
