build to resist hazards/ construire pour résister aux dangers

CONSTRUIRE POUR RESISTER AUX DANGERS/ CONSTRUIR PARA RESISTIR LOS PELIGROS/ BUILD TO RESIST HAZARDS DRAFT CONSTRUCTION MANUAL April 14, 2010

EARTHBAG HOW-TOS Patti Stouter, Owen Geiger, and Kelly Hart

Copyright 2010 Patti Stouter and www.earthbagbuilding.com

This work can be used according to the following Creative Commons License: Attribution Non-commercial 3.0

http://www.earthbagbuilding.com

BUILD TO RESIST HAZARDS: DRAFT CONSTRUCTION MANUAL WWW.EARTHBAGSTRUCTURES.COM

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MANYÈL SA A ANGAJE NAN FANMI YO AN AYITI, AN ESPWA KE YO KA RETE NAN KAY KI PI AN SEKIRITE.

THIS MANUAL IS DEDICATED TO THE FAMILIES OF HAITI, IN HOPE THAT THEY MAY BE ABLE TO DWELL IN SAFER HOMES.

CE MANUEL EST DEDIE AUX FAMILLES D'HAÏTI, DANS L'ESPOIR QU'ILS PUISSENT ETRE EN MESURE D'HABITER DANS DES MAISONS PLUS SURES.

ESTE MANUAL ESTA DEDICADO A LAS FAMILIAS DE HAITI, EN LA ESPERANZA DE QUE PUEDAN SER CAPACES DE VIVIR EN HOGARES MAS SEGUROS.

Tradui materyèl sa a ak translators yo entènèt nan Translate this material with the internet translators at http://www.google.com/ig?hlen\x26referrerign # max8. Traduire ce matériel avec les traducteurs internet à Traducir este material con los traductores de Internet en

Materyèl sa a se konesans ki pi bon sou dat ranfòse bilding ti sak sou latè. Li pral mete ajou jan nou jwenn plis konsèy teknik. Nou akeyi kòmantè pa toulede enjenyè ak Builders.

This material is the best knowledge to date about reinforcing small earthbag buildings. It will be improved as we gain more engineering advice. We welcome comments and advice by both engineers and builders.

Ce matériel est le meilleur des connaissances à ce jour sur le renforcement de petits bâtiments de sacs de terre. Il sera mis à jour comme nous obtenir des conseils plus techniques. Nous accueillons des commentaires à la fois par les ingénieurs et les constructeurs.

Este material es el mejor conocimiento hasta la fecha sobre la potenciación de pequeños edificios de sacos de tierra. Se irá actualizando a medida que ganan más asesoramiento en ingeniería. Damos la bienvenida a los comentarios de ambos ingenieros y constructores.

Kontakte nou nan anay ki nan lis ki sou paj wèb la Contact us at the email sites listed in the web page http://www.earthbagstructures.com/aboutus.htm. Contactez-nous à les e-mails répertoriés sur la page web Contacte con nosotros en el correo electrónico que aparece en la página web

http://www.google.com/ig?hlen

http://www.earthbagstructures.com/aboutus.htm


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3 CHEAP BUILDINGS: HAZARDOUS? 7 DESIGN EARTHBAG TO RESIST HAZARDS

SITE WORK 15 SOILS FOR EARTHBAG

18 HOW MUCH SOIL? & GRADING 20 CISTERNS

WALLS 24 FOOTINGS & WALL BASE REINFORCEMENT 28 STRUCTURAL MESH 29 CORNER REINFORCEMENTS 32 EXTERNAL WALL BRACING

OPENINGS IN WALLS 34 REINFORCING EDGES 38 ATTACHMENTS 41 LINTELS

45 OTHER OPENING DETAILS

ABOVE WALLS 49 BOND BEAMS 53 EAVES WIDTHS & PLASTER CHOICES

Image Credits:

Cover picture of project at Calvary Baptist Church at Delmas 83, Port au Prince, Haiti March 2010. Used by permission of Rodney Johnson. Page 8: Picture of the Sun House at Free the Kids courtesy of Father Theo and www.earthbagbuilding.com. Used by permission. Pate 10: Picture of builders in Sierra Leone courtesy of Shine On Sierra Leone and www.earthbagbuilding.com. Used by permission. Other photographs and drawings by Patti Stouter.




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CHEAP BUILDINGS: HAZARDOUS?

Many around the world need safe ways to build with cheap materials. In hazardous areas construction can be horribly expensive- and horribly confusing.

The results of not building safely may not be obvious at first. Unsafe buildings go up quickly. They look nice and are cheap. Often the differences become painfully visible when a crisis occurs.

Some hazards, like active volcanos, happen in very localized areas, but are hard to prepare for. These include flash floods and some chemically dangerous soils. Other hazards can sometimes be resisted but affect either localized areas or only well-sealed buildings. These include radon gas, avalanches, and permafrost settling.

Some hazards cause a lot of property damage, but do not as often kill or injure people. Careful building out of the greatest danger zones can lower levels of damage from swelling clay soils or wildfires.

It is tragic that other natural forces injure and kill many people around the world each year. These natural processes are so powerful that they cannot be resisted in the zones of greatest danger. Careful building can reduce the level of risk from these hazards for those who live in moderate danger zones:

• Tsunami:1 Locate 0.5- 2 km from coast and 15m or higher above sea level Maintain shelter belts of trees or mangroves towards the ocean

or build break walls (that can be closed) in the water Face buildings perpendicular to the sea and space buildings apart on roads Build on raised, open, waterproof foundations that extend deeply Build core walls of very strong reinforced materials Use hydro-dynamic shapes (rounded or angled corners) Include weaker wall and roof sections that will give to relieve pressure and allow waves to pass

through If far from higher ground leave strongly-rooted trees nearby or provide higher stories for shelter

1 Danbee Kim, Tsunami-Proof Building, http://web.mit.edu/12.00/www/m2009/teams/z/danbee.htm, retrieved 4-9-2010.

http://web.mit.edu/12.00/www/m2009/teams/z/danbee.htm


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• Land slide or mud flow:2 Locate away from the bases of steep slopes, especially of weathered shale or clay soil or with

springs or seeps Maintain deep rooted ground cover on slopes to naturally stabilize and de-water them Make sure runoff is never diverted to flow onto steep slopes Never add soil to the top of steep slopes or remove it from the base of slopes Excavate diversion channels and/ or build deflection walls to direct soil flow around buildings Face strongly reinforced buildings perpendicular to slopes and shape upslope ends hydro-

dynamically

• Liquefaction:3 Locate away from fine grained or deep soils that have high water levels in regions of earthquake

risk Find out if geologists can or have evaluated suspect soils (up to 30 m deep) Lower water levels in deep soils and build special spread or floating footings

The worst tragedies are those that could be prevented. Warning systems and evacuation plans are important for the next three types of hazard. But inexpensive buildings (including earthbag construction) can often be shaped or detailed to prevent the following natural forces causing disasters:

• Tornado: Build a shelter room or basement that is either not too well-attached to a light building, or at the

center of a well-reinforced structure Use very well-attached, heavy walls for the shelter room and fasten them well to a reinforced

roof and heavy foundation Use a securely latching reinforced door, and very small openings for ventilation on the shelter

room

2 Gary B. Muckle, Understanding Soil Risks and Hazards, USDA, (Lincoln, Nebraska: NRCS, 2004) 69- 70 Retrieved 4-9-2010 at

http://soils.usda.gov/use/risks.html.

3 Muckle, 74

http://soils.usda.gov/use/risks.html


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Flood: Raise buildings or living spaces above flood level Build strong walls with materials that can dry out without damage, especially materials without

internal voids Use either multiple deep footings with open spaces between them or a unified massive

foundation

• Hurricane: 4 Locate buildings above elevations subject to storm surges and/ or in the wind-shadow of hills Provide resilient plantings and / or erosion barriers at locations exposed to wave erosion Strengthen walls to resist wind pressure Fasten roofs securely with metal clips to strong, heavy walls or heavy foundations Build with materials that can dry out without damage, especially materials without internal voids Keep wind-driven rain out with special details like capillary breaks at footings and baffles on

vents Open shutters and doors outward and latch securely

• Earthquake:5 Isolate the base of a building from ground motion by a low-friction interface or shock absorption

in the footing Increase building flexibility or stiffness Keep weight low in the building by using lighter roofs and upper stories Use compact, symmetrical plans that unite walls and reduce vibration

• Earthquake (continued):

4 PATH, Build to Improve Storm Resistance, 5-21-2007. http://www.pathnet.org/sp.asp?id=12387, retrieved 4-9-2010

5 Various sources, including: Minke, Gernot, Construction Manual for Earthquake Resistant Houses Built of Earth, (Eschborn, Germany: Gate/ Building Advisory

Service and Information Network, 2001) 8- 9. Retrieved 4-11-2010 at http://www2.gtz.de/dokumente/bib/04-5487.pdf; Morris, Hugh, New Zealand: Aseismic Performance-Based Standards, Earth Construction, Research, and Opportunities, 60- 61 retrieved 4-9-2010 at http://www.getty.edu/conservation/publications/pdf_publications/gsap_part2b.pdf; Wikipedia, Earthquake Engineering retrieved 4-9-2010

http://www.pathnet.org/sp.asp?id=12387

http://www2.gtz.de/dokumente/bib/04-5487.pdf

http://www.getty.edu/conservation/publications/pdf_publications/gsap_part2b.pdf


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Locate buildings with a level ground-floor only slightly cut into existing slopes Tie corners together well and provide enough bracing perpendicular to walls Use monolithic or complex structures that share stresses even if a single element fails Have a three dimensional web of reinforcement that contains building elements even if cracking

occurs Note: Buildings can resist damage from higher levels of ground shaking than from ground

subsidence or displacement

Strongly reinforced, stable or heavy building walls are needed to resist many hazards.

The type of reinforcement and detailing that is appropriate to resist earthquakes will be strong enough for most other hazards. Walls designed to resist

earthquakes can be strong enough to resist winds up to 50 meters/ second.6

6 Australia/ New Zealand Technical Committee, Earth Buildings Not Requiring Specific Design (Wellington, New Zealand: Standards Council: 1999) 46


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DESIGN EARTHBAG TO RESIST HAZARDS

Earthbags are easy to build with. They cost very little if people have time for building.

Earthbags are heavy. When reinforced, earthbag walls can be very strong and stable. In addition earthbag walls also are non-flammable, nearly soundproof, and cannot be pierced by gunfire.

But how strong are they?

We want to know exactly how little reinforcement we can use. We want to know exactly how high we can build earthbags that will stay standing in earthquakes and floods.

We don’t know everything we want to yet.

In some places people have to have all the answers before they build. Some builders in these places have ignored questions by putting earthbags between wood or cement posts. Others pump all earthbags full of cement.

But in Les Cayes, Port au Prince, Haiti, earth-filled bags at an orphanage made a one-story building that was stuccoed with cement plaster. This was untouched when buildings nearby were damaged by multiple earthquake shocks this year.

Instead of overbuilding we can work with what we do know.


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We know that bearing walls can be better than post and beam systems in earthquakes:

• Monolithic bearing walls on floating foundations weather earthquakes better than post and beam construction on separate footings.7 • Straw bale walls contained by fishing net on a footing of gravel-filled earthbags passed a recent shake table test at the University of Nevada,

Reno. The structure withstood ground acceleration of 0.82g, double the record-breaking Mw 6.7 quake in Northridge, California in 1994.8

We know that structural skins are strong:

• Mesh with either cement or earthen plaster greatly increases the initial shear strength and stiffness of mud block walls.9

We know that geo-textiles are strong:

• Tens of millions of sand bags, placed mostly by volunteers, are effective each year at controlling floods. • Archaeologists use sandbags to support collapsing walls, and the military uses them for bunkers. • Geo-textiles combining soil with fabrics and/ or plants are preferred for stabilizing streambeds with serious erosion problems.10

• Earth-filled bags are almost 10 times stronger for supporting weight than wood stud walls.11

7 Khalili, Nader and Phil Vittore, Earth Architecture and Ceramics: The Superadobe/ Superblock Construction System (Building Standards Sept-Oct. 1998) 27.

Retrieved at www.earthbagbuilding.com/pdf/buildingstandards_calearth.pdf.

8 Charly Champion, Seismic Response of Innovative Straw Bale Wall Systems and System Identification, Unpublished thesis (Reno, Nevada: University of

Nevada)

9 Torrealva, Daniel, Julio Vargas Neumann, and Marcial Blondet, Earthquake Resistant Design Criteria and Testing of Adobe Buildings in Proceedings of the

Getty Seismic Adobe Project 2006 Colloquium (Peru: Pontificia Universidad Católica del Perú: 2006) 6. Retrieved 4-9-2010 at www.getty.edu/conservation/publications/pdf_publications/gsap.html.

10 United States Department of Agriculture, Stream corridor restoration: Principles, processes, and practices, (Washington, DC: Natural Resources Conservation Service. 1998, revised 2001) 8-62 to 65. Retrieved 4-11-2010 at http://www.nrcs.usda.gov/stream_restoration/.

11 Daigle, Bryce Earthbag Housing: Structural Behavior and Applicability in Developing Countries (Kingston, Ontario, Canada: Queen’s University: 2008) thesis

for Masters in Civil Engineering 130 retrieved at www.earthbagbuilding.com.

http://www.earthbagbuilding.com/pdf/buildingstandards_calearth.pdf

http://www.getty.edu/conservation/publications/pdf_publications/gsap.html

http://www.nrcs.usda.gov/stream_restoration/



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We also know that earth building materials are strong:

• Good adobe blocks are many times stronger than the weak sand-cement blocks that have been commonly used in places like Haiti. Adobe blocks have a compressive strength of at least 250 pounds per square inch dry, and 200 psi wet. Although different soils have strengths of 70- 680 psi, they can easily be tested with simple lever devices. 12

• Ancient buildings in Yemen of adobe are four to eight stories in height. • Many houses in Europe are of earth, like the 6-story house built of rammed earth in Weilburg, Germany

dating from 1828.13 • Soil of 12-15% clay that is tamped repeatedly can reach compressive strengths of 400- 600 pounds per

square inch. 14 • Earthbag builders use informal tests on tamped and cured earth-filled bags to evaluate soil, like holding

the weight of a 3/4 ton truck without deforming. 15

Earthbags are similar in size or slightly larger than the largest traditional adobe blocks. They are tamped in a way that compacts and strengthens them. Walls of earthbag can be designed to carry weight and resist lateral forces (winds and earthquake motion) the same way that adobe can.

12 A 2- 3 m (6-10’) long pole with some chain and a person’s weight can test a small block of 15 x 7 x 5 cm (6 x 3 x 2 inches). Wolfskill, Lyle, Handbook for

Building Homes of Earth: Appropriate Technologies for Development.(Washington, DC: Department of Housing and Urban Development, Peace Corps Information Collection and Exchange Division, 1981) 34- 38. Retrieved 4-11-2010 at http://www.eric.ed.gov/ERICDocs/data/ericdocs2sql/content_storage_01/0000019b/80/34/73/03.pdf.

13 Minke, Gernot, Building With Earth: Design and Technology of a Sustainable Architecture, (Basel, Germany: Birkhãuser, 2006) 13

14 The same soil can be 10- 14% stronger when vibrated and tamped than when compressed once into a CEB. Minke, Building With Earth, 44

15 Hunter, Kaki, and Donald Kiffmeyer, Earthbag Building: The Tools, Tricks and Techniques, (Gabriola Island, BC: New Society Publishers, 2008) 21

http://www.eric.ed.gov/ERICDocs/data/ericdocs2sql/content_storage_01/0000019b/80/34/73/03.pdf


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We have learned that existing earth buildings can resist earthquakes well with some reinforcement:

• Old adobe buildings reinforced on the exterior weathered major earthquakes that destroyed unreinforced but similar buildings nearby. In some cases reinforcement consisted of wide strips of 1mm wire mesh (spaced at 2cm) fastened by nailing through metal bottle caps, and covered with sand-cement mortar. These were applied at corners, top of walls, and intermittently spaced in long walls.16

And we have learned how to build earth buildings safely in the highest seismic risk regions:

• New Mexico, which includes the UBC seismic zone 2b with frequent earthquake activity, allows earth block and rammed earth construction. More than 75,000 homes of adobe or rammed earth had already been built there by 1996. 17

• New Zealand, with high seismic activity, has historic earth buildings that have survived multiple major quakes. They have a code that specifies parameters for adobe, rammed earth, and compressed earth block buildings that do not require special engineering.18

Earthbag walls have more horizontal strength than traditional adobe because of their interface of barbed wire and fabric. They are tied together vertically with intermittent bands of wire or strapping of cord and /or rebar. Their higher tensile strength and flexibility, like straw bale construction, may make earthbag walls more intrinsically suited than adobe or rammed earth to areas subject to earthquakes.

Earthbag walls can easily be built with extra reinforcing. It is simple to attach a flexible fishnet or chicken wire grid to building walls. Rebar can be hammered through multiple bags. Strips or grid of metal or plastic can be laid between bag courses.

Earthbags are better suited than adobes to damp climates. Because earthbags can be filled with a wider variety of soil types than those used for adobe, a wider variety of plasters can be used than on unstabilized adobe blocks. Although cement plaster degrades adobe or CEB that are made without cement, it can be used on bags filled with certain types of soil without any cement or bitumen stabilization.

16 Blondet, Marcial and Gladys Villa Garcia M., Adobe Construction (Catholic University of Peru: 2005?) 5. Retrieved at www.world-

housing.net/uploads/adobe.pdf.

17 www.deatech.com/natural/cobinfo/adobe.html.

18 New Zealand Standards. Earth Buildings Not Requiring Specific Design provide detail and plan standards for up to 600 m2 single story buildings of these earth

materials (or a light frame story above an earth ground floor) in their most risky seismic region. Information about the standards and links to purchase them are available at http://www.earthbuilding.org/nz/standards.htm.

http://www.deatech.com/natural/cobinfo/adobe.html

http://www.earthbuilding.org/nz/standards.htm


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To resist waves, short-term flooding, hurricanes or tornados earthbags need some additional modifications. These can include special shapes, deeper footings, and/ or extra stabilization or reinforcement. Their woven polypropylene skins allow earthbags to resist short-term soaking better than adobe. Adding lime or cement or bitumen to earth-filled bags can create a building material resistant to prolonged flooding.

Plans are underway for more engineering tests of earthbags. As results are reported, information will be posted at www.earthbagstructures.com. This information may allow us to reduce or modify recommendations for reinforcement because of earthbag’s qualities of flexibility.

The information we now have is enough to use earthbags to build simple, small buildings safely. People building in high seismic risk areas will need to decide what sort of strategy they are most comfortable with to ensure their building designs will survive earthquakes.

SUCCESSFUL STRATEGIES FOR EARTH BUILDINGS THAT SURVIVE EARTHQUAKES

Adobe or cob buildings that have survived quakes set a good precedent for small earthbag buildings in high seismic risk areas. They have:

• Good footings that do not move apart during earthquakes

• Load-bearing walls with a height 5 or 6 times their thickness (thick walls experience reduced earthquake stresses)

• Perpendicular bracing provided by intersecting walls or piers evenly spaced throughout the plan

• Openings small and well-spaced, with at least 1m between openings or openings and corners

• Very limited un-braced walls- only short walls like buttresses extend alone. (1 or 1.2 m maximum may be best unless they step down in height)

More information about safe dimensions and plan types for earthbag is available in the booklets Choosing Shelter Plans for Hazardous Areas or Choosing House Plans for Hazardous Areas at www.earthbagstructures.com/choosing/choosing.htm..

The kind of reinforcement most successful at helping existing adobe structures survive earthquakes may be the best to use on earthbag structures until further testing can be done. Adobe buildings that have a plastered web of reinforcement with some flexibility suffer less damage than buildings reinforced with

http://www.earthbagstructures.com

http://www.earthbagstructures.com/choosing/choosing.htm


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welded wire mesh or stiffer materials. Reinforcement that has a compatible level of give to the amount of flexing between layers of stacked adobe blocks enables adobe buildings to survive higher levels of shaking without damage. Engineers testing existing buildings recommend a reinforcement web:

• of a grid of horizontal and vertical elements

• that are connected to each other

• fastened frequently to the wall

• are well fastened to the bond beam or top of wall reinforcement.

Successful materials have included:

• plastic mesh

• cord

• nylon straps

• natural materials like bamboo, wood poles, cane, or vines.19

These existing structures often have wood instead of reinforced concrete bond or ring beams. Bond beams transmit point roof or ceiling loads uniformly to the full length of the wall as well as reduce deflection along the length of the wall. Bond beams must stiffen the wall and be continuous, but some hinge action at corners is acceptable. Bond beams that can flex somewhat vertically over their length allow force to be transmitted in less damaging ways. If reinforced

concrete bond beams are used, they should be the full width of the walls but no more than 15 cm (6”) thick.20 Wide corrugated metal strips sandwiched near

the top of an earthbag wall may work more effectively than concrete for a bond beam. They provide effective horizontal bracing, but can flex vertically during earth vibrations.

The function of roof, ceiling, or upper floor structures at stiffening buildings should also be recognized. Collar ties or upper level floor joists can provide significant bracing to ground floor earth walls when connected to a well-anchored bond beam. When combined with wide boards or sheet floor or roof materials they can become a structural diaphragm. Diagonal cabling may also be an effective method of bracing wall tops when plywood or wide boards are not included in floor or roof construction.

19 Torrealva, 9

20 This article discusses the effect of conventional engineering formulas recommended by current US adobe codes (New Mexico, Arizona): Fred Webster, Some

Thoughts on Adobe Codes. Retrieved 4-12-2010 at www.deatech.com/natural/cobinfo/adobe.html.

http://www.deatech.com/natural/cobinfo/adobe.html


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EXISTING EARTH BUILDING CODES Some people building small structures (600 m

2 or less) without special engineering help may be reassured by the New Zealand code Earth Buildings Not

Requiring Engineering (NZS 4299). It includes a complex check of wall bracing supplied by the buildings own walls, adjusted for different wall heights, levels of reinforcement, roof weights, and conditions with lofts or upper levels. NZS 4299 also has standards for size of eaves and levels of durability required for exterior earth materials in different wind environments that may be helpful to those designing for humid climates.

But the New Zealand code also insists on reinforced concrete for footings in high seismic risk areas. This may unnecessarily limit the inherent flexibility of earthbag. It allows wood bond beams in high seismic risk areas if united to a structural ceiling or roof or floor diaphragm. But because it has been written with adobe and rammed earth in mind, it does not include metal bond beams.

And the New Zealand code’s definitions of what constitutes reinforcement may not apply to small earthbag buildings. Earthbag’s matrix of bags and wire provide more reinforcement than adobe. New Zealand’s guidelines for rammed earth may be more applicable than the guidelines for adobe, because they do not require horizontal reinforcement. If barbed wire is laid in earthbag outside of corner rebar reinforcement, it contributes to horizontal reinforcement. But the requirements for vertical rebars in rammed earth may also be more than necessary for ordinary earthbag buildings that are not exposed to direct floodwater or waves. Required spacing starts at 1.15 m on center average for 2.4m ht. walls, and declines to 0.5 m on center for 3.3 m height walls).

Current earth building codes (like those in the southwestern US or New Zealand) should not be slavishly followed for earthbag construction. An engineer influential in developing the 1998 New Zealand code believes the specifications assuming great needs for tensile reinforcement need to be re-examined. He mentions the stability provided by mass in unreinforced earth buildings, and states that more testing is needed to explore the actual performance of structures

with little tensile strength.21

Most codes use strength design concepts developed for reinforced concrete and reinforced fired brick walls. Adobe (and earth bags as well) do not form a tight bond around rebar reinforcement in the same way that concrete does. Wall reinforcement can actually reduce adobe building strength in earthquakes by concentrating stresses. Anchor rods fastening bond beam to walls can also concentrate stresses unless they are more closely spaced at 30- 60 cm (12-24”).

Earth building codes to date include a level of internal reinforcement that has not been proven successful by testing.22

21 Morris, 64.

22 Webster


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The type of intensive reinforcement with rebar recommended at present by earth building codes may not be as damaging to earthbag as it is to adobe, because of earthbag’s cohesive strength from the woven bag fabric. But it may be unnecessary.

The construction techniques in this booklet are chosen because they are low-tech and low-cost. Combined with good quality control, they can create buildings and site structures strong enough to survive hurricanes and resist earthquake damage. Good quality construction includes:

• appropriate siting • plumb and level walls • adequate tamping • strong bags • correct soils • appropriate building dimensions • maintenance of exterior plaster layers and roofs

These are all necessary to create hazard-resistant buildings. More information on these topics is available at www.earthbagstructures.com or www.earthbagbuilding.com.

All the information and details that follow are intended for small single story houses built of 38 cm (15”) wide walls of 50# bags filled with an earth mix containing some clay. Rebars are to be 12 mm diameter (#4 or 1/2 inch) diameter minimum.

These details and notes are general and may not apply in all situations.

Engineers or expert earthbag builders can make specific recommendations better suited to your site, your soil, and your particular building configuration.




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SITE WORK Earthbag is especially inexpensive if soil can be found on the building site. The yard can be sloped to drain or to excavate a cistern to save rainwater while digging enough soil for a small house. It is important to locate the building floor level correctly to allow enough soil to be dug out without leaving low areas that will not drain well.

A single small 2.4m x 3.3 m (8’ x 11’) shelter room can take 8 cubic meters (10 cubic yards) of good subsoil. If it is located on a gentle slope, the ground level may have to be lowered 0.8- 1 m (32 – 29 inches) at the uphill side of a 4m x 5m (13’ x 16’) area to provide enough soil for this tiny building.

A 3m x 6m (10’x 20’) building can take 21 cubic meters (700 cubic feet) of soil. These figures do not include soil needed for buttresses or benches.

In some parts of the world people begin house building with a sturdy cistern beneath the floor. This saves precious space in the cities, and can provide soil for earthbags. But this makes walls higher and requires stronger buildings. To keep earthbag walls strong to resist earthquakes without using a lot of cement, cisterns are best located a meter (3 feet) away from earthbag building walls.

SOILS FOR EARTHBAG Many soils become very strong in earthbags. Soil usually needs to have a little clay in it. Soil used for roads (called road base) usually works well. Test subsoil to find out if it is strong enough without any cement or lime added. It is best to make a test bag and let it dry for a couple of weeks. But some information can come instantly by squeezing some, dropping small balls, and rolling it. More testing information is at www.earthbagstructures.com.

A couple of handfuls without any topsoil or debris must be dry (dry it in the sun or in an oven). See how it acts when it is barely damp enough to hold together.

This soil is very sandy. It feels gritty between the fingers, and barely holds together until it is bumped. Extra water won’t make it hold together.

This soil is too sandy for ordinary earthbags. It could be used with a lot of clay mixed into it. It could be used with wood bracing during construction until a reinforced cement plaster can be completed.



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This soil feels gritty, but it will hold together a little. It is a sandy soil with some clay or silt.

Make the soil into several 4 cm (1.5 inch) balls and drop them one at a time from 1.5 m (5’ height).

This was one ball that shattered. The soil makes a ball if squeezed very hard, but it doesn’t hold together well. This soil has very little clay in it.

If a soil like this stains your hands, it contains a little clay. It may work for earthbags although it doesn’t have enough clay for adobe or CEBs or earthen plaster. A test bag will show you how strong the soil will be when tamped.

If a soil like this colors your hands but can be brushed off it is probably sand and silt with little clay. Silts are weak soils and are not good for filling earthbags unless cement and lime or bitumen is added.

This soil split into a few pieces when dropped. It has enough clay to make good earthbags.

If a soil doesn’t feel gritty in your fingers but only holds together this much it might have a lot of silt. It would be a good idea to test a smooth-feeling soil like this in a bag, or ask someone who knows earth construction or soils more about it.


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This soil makes a sticky lump, even when it is only barely damp enough. If it is cut with a table knife, the cut surface looks smooth and shiny. It contains clay.

Make it into a few 4 cm (1.5 inch) balls and see what happens when they are dropped from 1.5 m (5’) high.

If it leaves a wet spot it’s too wet- mix in some dry soil until it doesn’t look shiny any more.

If the balls flatten like this one with few or no cracks, they are 15% or more clay.

Clay soils can be good for earthbag or not, depending on the amount and kinds of clay. Do a ribbon test to find out more about the clay.

Take moist soil, remove any pieces of grit, and knead it in your fingers to mix it very well and develop its strength. Roll it on a flat surface or roll or press it very carefully into three shapes these different sizes. Then cut each 4 cm (1.5 inches) long.

6mm thick (a little less than 1/4 inch) 4mm thick (a little more than 1/8 inch) 2 mm thick (if possible- halfway between 1/8 and 1/16 inch)

If you can hold up a 6mm thick piece by one end and it doesn’t break it has some plastic clay, but can work in earthbags.

If you can hold up a 4mm thick piece by one end and it doesn’t break it has too much plastic clay. This soil will shrink and swell too much to use in earthbag, or to put a building wall on it either. It may make a good earth plaster, but build on different soil.

If you can make a 2mm thick piece, and can hold it up by one end without it breaking apart, it is a very plastic soil. This might be good for making pottery, but it is probably not good for building.


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HOW MUCH SOIL? If your soil is rocky, estimate how much of it is rock. You will need to dig up a larger area to get enough soil.

If you have to buy soil for building, some discarded material may be less expensive. Reject sand or ‘crusher fines’ are soils left over from making gravel and/ or washed sand sold for concrete work. Test a small amount to see if it will work well for building before you order a truckload.

These figures are for the standard 22 kilogram or 50 pound bags. Adjust for larger or smaller bags.

Bag size: 38 cm wide x 12.5 cm high x 60 cm long, holds almost 30 liters, compacts to 670 cm2

of wall space when tamped.

15” wide x 5” high x 2’ long, holds about a cubic foot, compacts to about 0.70 square foot of wall space when tamped.

Wall height 2.4 m 7’-10” 2.7 m 8’-10” 3.0 m 9’-10”

Requires per linear meter foot meter foot meter foot

Amount of soil 1 cubic meter3 11 foot

3 or 4/10 yard

3 1.1 meter

3 12 foot

3 or 0.44 yard

3 1.25 meter

3 13.5 foot

3 or 1/2 yard

3

Soil is not needed for openings like windows and doors, but about 10% extra is a safe factor to cover mistakes or small changes. Better to have too much than not enough… But for heavy clay soils you should dig up at least 10% more, because clay compacts more than other soils.

If cement and/ or gravel are available you can dig out a cistern to save rainwater and use the soil to build the house. This is how much soil a cistern can provide. (Dimensions are to outside of cistern walls.) Less soil will be left over if earth-filled bags are used to build the walls, more if gravel or rubble from other locations are used to build with:

3700 LITER (1000 GAL.) 4.2- 8.4 CUBIC METERS- 2.6 M DIAMETER, 1.5 M HIGH OR 5.5- 11 CUBIC YARDS- 8’-6”

DIAMETER, 5’ HIGH 6000 LITER (1600 GAL.) 6.5- 12.2 CUBIC METERS- 3.8 X 2.3 M, 1.5 M HIGH OR 8.5- 16 CUBIC YARDS- 12’-6” X 7’-6”, 5’ HIGH


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GRADING FOR DRAINAGE Before building, land may not seem to have a water problem. Rain soaks into the open ground.

After building, rain runs off immediately from the roof, and quickly from the yard. There is a lot less of open ground to soak up the rain. If the earth was made firmer by machines or a lot of people walking, what is left won’t soak up the rain as well as it used to.

Saving rainwater in a large enough cistern can give you drinking water and help prevent damage water can cause downhill.

Very flat land can end up with soggy areas that breed mosquitoes. Very steep land can have streams that run into your house or wear away at your walls.

Buildings resist earthquakes best if the ground level floors do not step up or down.

They also resist earthquakes best if they do not have a lot of soil heaped up against the building walls. To be safe in earthquakes it is better to dig some soil out of the higher side of the hill and use a separate wall if necessary.

A house on a slight mound is less likely to have water

entering the home. The ground should slope down in all directions for at least 3 m (10’). This slope should be at least 1:50 (1 inch in 4’) for rain to run off well. A swale (gently sloping drainage ditch) on the uphill side of the house should start 6 cm (2.5 inches) lower than the level outside the door if it is 3m (10’) from the house. Leave enough room for the swale to fit around future buildings or additions.

To get enough soil to build with you will need to dig out more soil on the uphill side. When you choose where the house will go, the floor of the house will need to be a little higher than the ground level on the downhill side. If there is loose rock or rubble nearby, you can use that to fill inside the house to raise the floor level up.

Additional rock or rubble is safer to use for benches or retaining walls instead of house walls.


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CISTERNS Materials: Bags and/ or tubes, gravel, cement, #4 (1/2”) minimum rebar, galvanized metal mesh, poly or nylon fishnet, latex waterproofing, pipes, strong poly or nylon cord, and lid.

Locate any cistern 1 m (3’) or more from any proposed building walls. Be careful to not disturb the soil where the building will be placed.

These designs are only intended for frost-free climates. Models included are sub-grade cisterns, but round water tanks can be built at grade next to buildings.

Left: Cross-sectional view

Bags filled with only earth are not recommended for underground use. They can be damaged by high water levels or by leaking from the cistern itself. This can cause the walls to fail.

The first 3/4 meter (30”) can be built with bags filled with angular gravel if it interlocks well enough to be stable. Bag and test your gravel to be sure. The upper courses must be filled with rubble or gravel mixed with a slurry of cement, or earth mixed with enough cement to fully stabilize it.

The curving top is built of ferro-cement tied to a thick interior cement plaster reinforced with mesh.

Left: Use a pole compass to build round walls Pound a 60- 90 cm (24- 36”) pipe into the ground at the center of the cistern location. Put a 1.6 m (5’-3”) height round stake or smaller pipe inside. This must be perfectly plumb. Slide a pipe clamp or clip onto the stake. This will be adjusted to the height of the bag course you are measuring. Then add a ring or a short piece of pipe above it. Tie a sturdy rope or fasten a metal arm to this moveable ring or piece of pipe.


21

CISTERN CROSS-SECTION Note: Provide bracing if necessary until the cement plaster interior is completed.

Sac/ Bag: Doubled poly bags filled with gravel. Angle bag ends to center of dome to accommodate curve. Fasten interior layer of metal mesh to exterior layer of fishnet every 2 courses and 60 cm (24”) horizontal.

Fil de Fer/ Wire: Use 2 rows of barbed wire between each layer. Tube/ Tube: Tubes or bags filled with stabilized earth or with gravel or rubble in a cement slurry. Test to find the best ratio of cement and/ or lime needed for your fill material.

Terre/ Soil: Place bag walls on undisturbed subsoil.

Barre/ Rebar: Hammer rebar for ferro-cement framework through upper courses of bags or tubes before cement sets.

Ciment/ Cement: Bend vertical rebar and wire horizontal rebar to it to form top. Attach mesh for top following best practices for ferro-cement. Place reinforcement of mesh or rebar for tank floor.

When ferro-cement framework is complete add a thick cement finish plaster layer inside of tank and tank top, and pour reinforced concrete floor. Complete as much as possible in one day to avoid cold joints between separate cement areas, which will be more likely to leak. A latex cement additive will also improve waterproof quality. Trowel interior cement smooth for ease of cleaning. Add rough cement plaster to exterior.


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ROUND 3700 LITER (1000 GALLON) CISTERN PLAN

Bâtiment/ Building: A cistern should be located at least 1m (3 feet) from an earthbag building wall.

Pipe/ Pipe: Build a ferro-cement pipe with an overflow spout, sloping up from the tank to 30 cm (12”) above grade. This pipe must be larger than the gutter downspout, and be screened. Add a second pipe for a water supply line.

Citerne/ Cistern: The cistern walls and roof must be backfilled and covered.

Trappe/ Hatch: Provide a hatch of 2.5 cm (1”) thick cast concrete or heavy metal that overhangs the scuttle beneath it. The hatch should be at least 30 cm (12”) above grade to prevent contamination of the stored water.

Do not backfill until ferro-cement structure has completely cured. Use scrap cardboard or straw to protect bags from damage if backfill material contains rocks.

Note: Locate overflow spout above stone water spreader in swale.


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OBLONG 6000 LITER (1600 GALLON) CISTERN PLAN Bâtiment/ Building: A cistern should be located at least 1m (3 feet) from an earthbag building wall.

Pipe/ Pipe: Build a ferro-cement pipe with an overflow spout, sloping up from the tank to 30 cm (12”) above grade. This pipe must be larger than the gutter downspout, and be screened. Add a second pipe for a water supply line.

Citerne/ Cistern: The cistern walls and roof must be backfilled and covered. This oval cistern will be stronger if the straight wall section includes a pier on each side.

Trappe/ Hatch: Provide a hatch of 2.5 cm (1”) thick cast concrete or heavy metal that overhangs the scuttle beneath it. The hatch should be at least 30 cm (12”) above grade to prevent contamination of the stored water.

Do not backfill until ferro-cement structure has completely cured. Use scrap cardboard or straw to protect bags from damage if backfill material

contains rocks.

Locate overflow spout above stone water spreader in swale.


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WALLS Earthbag walls must be built carefully on solid footings, braced well, and tied together well at the top to resist hazards.

FOOTINGS Reinforced concrete footings can be built for earthbag buildings. It makes sense in areas where the ground freezes deeply, or where rock is not available. Rubble footings are used in many parts of the world where the ground never freezes. Rubble footings may be safer than poorly mixed concrete. If reinforcing steel is too expensive, rubble footings can be strengthened without rebar. Earthbag buildings, like adobe or straw bale buildings, can flex to survive earthquakes. Rubble footings with some wall base reinforcement may be a better solution for earthbag construction in high seismic risk areas.

RUBBLE FOOTINGS Materials: rubble, stone, gravel

Tranchée/ Trench: The bottom of the trench must be level and at least 20 cm (8”) deep on the downhill side of the building. It must be dug down to firm, undisturbed subsoil. The trench must be 45- 50 cm (18- 20”) wide, as wide as the bags and the plaster layers both inside and outside.

Gravier/ Gravel: Use finely crushed rubble or gravel to fill 3 courses of doubled poly bags for a footing.

Sol/ Floor: Fill the building interior with rubble or clean fill and earth.

Décombres/ Rubble: Use a 12- 15 cm thick layer of rocks and pieces of rubble mixed with gravel for the trench footing.

Ouverture/ Opening: Make sure that two courses of bags fit beneath the floor level at the door.

Décombres/ Rubble: Set the floor level 10 cm (4”) below the top of the third course of footing bags. If a concrete floor is added later it will still be below the earthbag walls.


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WALL BASE REINFORCEMENTS: MESH FOOTING CONFINEMENT Materials: Plastic or galvanized metal mesh, poly bags, rebar, metal or plastic fasteners.

If reinforced cement footings are not used in earthquake prone areas, heavy mesh or geogrid can help to confine the wall base. Structural mesh on the walls is strengthened by earth or cement plaster, but mesh at the footing level should be much stronger and resistant to corrosion.

Tranchée/ Trench: The footing trench must extend under all the walls and doorways. Place a 12- 15 cm (5- 6 inch) thick layer of rubble and/ or gravel.

Latte/ Mesh: Place a 60 cm (24”) wide minimum strip of sturdy mesh around the outside edge of the entire foundation. Overlap edges 30 cm (12 inches) minimum and fasten securely with wire or sturdy plastic ties.

Gravier/ Gravel: Lay three courses of gravel-filled bags on straps that will be used to secure the bags to the mesh.

Latte/ Mesh: Keep overlap joints away from corners. Bend the mesh over the bag layer if necessary. If desired, several strips of heavy wire or cord can be used to bind around the entire footing outside the mesh.

Sangle/ Strap: Fasten mesh securely every 60 cm (24”) or more often with sturdy water-resistant straps or cord around footing bag layers.

Barre/ Rebar: Hammer 45 cm (18 inch) lengths of rebar into corner bags and/ or all footing bags.


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WALL BASE REINFORCEMENTS: CORRUGATED METAL REINFORCEMENT Materials: Corrugated metal strips, poly bags, rebar, 7.5 cm nails, metal or plastic fasteners.

If reinforced cement footings cannot be used in earthquake prone areas, metal can help to reinforce the wall base.

Bande/ Strip: Place 15- 20 cm (6-8”) wide strips of corrugated metal on the center of the entire first course of earth-filled bags, including under all door openings. Overlap strips 30 cm (12”) minimum at ends. Use 7.5 cm nails to pin at overlaps and at corners to the bags below.

Sac/ Bag: Earth-filled bags are laid on top of the three layers of double bags filled with gravel that form the footing below.

Barre/ Rebar: Hammer 45 cm (18”) lengths of rebar into each bag at the second course of earth-filled bags to hold the corrugated strip below in place. Space rebars 30- 60 cm (12- 24”) apart, and drive in at alternating 15 degree angles to interlock well to bags. Bend the tip of the rebar over.

Gravier/ Gravel: Three courses of gravel-filled bags will prevent dampness from damaging earthbags filled with soil alone. If soil is to be backfilled higher against the walls, use enough courses of gravel bags to keep earth-filled bags 15 cm (6”) above finish grade as well as the floor level.


27

WALL REINFORCEMENTS: Earthbag is very strong in compression (carrying loads) but can benefit from additional reinforcing in key locations, including corners, to resist lateral movement.

Mesh with a thick plaster coating becomes a reinforced shell. It can be very effective at help earthbag walls resist wind loads and earthquake forces. Plastered mesh transmits lateral forces safely and and reduces cracking of plaster. But most importantly, it confines separate earth units if severe wall cracking occurs, and prevents walls from falling outward, or apart.

All earthbag walls should be tied together vertically at least every 24″. Nylon strapping, the kind used to secure loads on shipping pallets, makes an excellent tie down. Wrap over the bond beam and under the wall and then cinch down with special tool and fasteners. All fasteners must be strong poly or nylon cord or strapping or galvanized metal, and protected with an earth or cement plaster.

Because earthbag is also a flexible form rammed earth, walls can be a little bit soft or flexible until they harden and cure. This process usually takes a couple of weeks if a wall is covered from rain. Temporary bracing can be used during construction. Some of these reinforcement techniques will also add stiffness during the building process.

Corners can be strengthened with metal, by overlapping or extending them, or by curving them. Walls can be stiffened by corrugated metal bracing, piers, buttresses, or by curving or jogging them.


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STRUCTURAL MESH Materials: Cord, some type of plastic or galvanized mesh- possibly poly fishnet, plastic plasterer’s lath, wire lath, or chicken wire

The use of well-plastered mesh has proven effective at keeping adobe and other masonry buildings from failing during severe earthquakes.

Latte/ Mesh: Start mesh underneath the lowest gravel bags used for the footings. When the walls are completed pull it up and over the bond beam. Overlap mesh at least 30 cm (12”) and keep seams at least 60 cm (24 inches) from corners.

Cord/ Twine: Lay 60- 70 cm pieces of strong twine across the bags every fourth course and every 60 cm (24”) horizontally along the wall. Use this to firmly tie the mesh each side of the walls together.

Sangle/ Strap: These straps form part of the metal bond beam.

Plaque/ Plate: Fasten the mesh securely by stapling into the wood top plate, or nailing and bending the nails over to hold it firmly in place without slipping.

Barre/ Rebar: These rebar pins attach the top plate and sandwiched metal bond beam to the wall.

Note: Stronger mesh may be helpful at corners or above doorways where stresses may be concentrated. A good plaster layer of earth or Portland cement stucco is necessary to create a structural skin that strengthens the building.


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CORNER REINFORCEMENT: REBAR Materials: Rebar

Barre/ Rebar: When walls reach 1.5 m (60”) height, hammer a 1.5m (5’) long piece of rebar through the corner bags.

Sac/ Bag: Always alternate bags at corners and stagger joints for strength.

As high as possible on the finished wall, hammer a second rebar of the same length in. It will overlap the first.

This is the simplest way to strengthen corners of earthbag buildings.


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CORNER REINFORCEMENT: MESH Materials: Sturdy mesh of galvanized metal or plastic, bamboo strips or steel angle or pipe or tubular steel, twine or cord

Latte/ Mesh: Place a 1m (39”) wide strip of sturdy mesh on the outside of the corner from top to bottom.

Cord/ Twine: Fasten the exterior mesh securely to the inside corner at every other course.

Vertical/ Vertical rod: Use metal or bamboo rod or additional mesh placed on the interior corner.

Sac/ Bag: Alternate earth-filled bags at corner.

Bamboo is very strong and flexible for reinforcing cement or earth construction. It can be either well encased in earth or left uncovered for inspection. Termites are very persistent. In hot regions they may be able to tunnel through earth floors. Bamboo (or wood) should be covered with thick earthen plaster that contains

something like borax to deter termites if it is not left uncovered inside so that it can be checked and replaced if damaged.


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CORNER REINFORCEMENT: CORRUGATED METAL Materials: Corrugated metal roofing, rebar, nails, strapping or twine

Barre/ Rebar: Drive 60 cm (24”) long rebar through corrugated metal strip at the corner to tie the reinforcement to the wall below. Repeat rebars at ends of metal strip or every 60 cm (24”).

Bande/ Strip: Cut pieces of corrugated metal roofing into strips 20- 30 cm (8- 12”) wide and at least 75 cm (30”) long. Overlap at corners and nail them into the bag below.

Sangle/ Strap: Use strong cord or mesh with wire or strapping every 60 cm (24”) to secure three layers of bags tightly around the metal.

Sac/ Bag: Stagger joints of earth-filled bags and alternate at corners.

This corner reinforcement stiffens and strengthens as well as unites walls if repeated every 5 bag courses.

Galvanized metal lasts well when exposed to rain and damp air. But if metal is well incased in dry earth in a roofed building, and has been firmly tamped, it does not need to be galvanized.

Corrugated metal or geogrid may also be useful to unite walls just below the window sill level.


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EXTERNAL WALL BRACING: BUTTRESSES Materials: Extra bags and barbed wire

Buttresses strengthen corners without rebar, and stiffen straight walls. Straight walls need a buttress or pier, intersecting interior wall, or a minor corner every 3- 3.5 m (10’- 11’). They also make it easier to add on earthbag to extend houses in the future.

Buttresses can be straight, sloping, or stepped. Benches or wider wall bases will also strengthen straight walls if the bags are well woven into the wall.

A vertical-edged buttress must stick out from the wall at least 60 cm (24”), and a sloping or stepped buttress 75 cm (30”).

Left: First Course

Fil de fer/ Wire: Lay barbed wire between each course. Loop wire from one wall into buttresses and out the other wall.

Sac/ Bag: Extend one wall out into the buttress.

Left: Fourth Course

Mur/ Wall: Stagger bag joints on all walls.

Contrefort/ Buttress: Criss-cross bag courses at buttressed corners every course to fasten it into the wall.

When plastering, clay-rich earth can be added to create curves or add decorations.


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EXTERNAL WALL BRACING: PIERS Materials: Extra bags and barbed wire

Straight walls need a buttress or pier, intersecting interior wall, or a minor corner every 3- 3.5 m (10’- 11’). A pier is usually a thickened wall section. It only projects out from the wall the width of a single bag.

Criss-cross the bag courses to tie the pier well into the wall.

Lay barbed wire between layers so that it loops from the wall out into the pier and back into the wall.

Left: Piers at a corner


34

OPENINGS IN WALLS Earthbag benefits from additional reinforcing at the edges of all wall openings.

All earth-filled bags at doorway openings should have the bag bottom pre-tamped as they are filled. Face this firmer bag bottom towards the opening to simplify plastering. Locate openings or adjust bag sizes near opening so that partial bags are not too short, but 30 cm (12”) long minimum.

Use wood, metal, or strawbale forms in window or door openings to allow adequate tamping while maintaining neat and plumb edges of openings.

Clay-rich cob building techniques can be used to add trim to building elements including the edges of openings. Metal or plastic mesh is helpful to reinforce this type of earth decoration.

REINFORCING EDGES: REBAR Materials: Rebar

Sac/ Bag: Face bottoms of bags to openings.

Ouverture/ Opening: Keep edges of bags straight and plumb.

Linteau/ Lintel: Level of the bottom of the future lintel.

Barre/ Rebar: Drive a rebar 30 cm (12”) longer than the height of the window opening through the bag wall. Drive it vertically through the center of the smallest bags along the opening edges.

For a door use 2 rebars 1.2- 1.5 m (4’-5’) long overlapped 45- 60 cm (18- 24”).

If a poured concrete lintel is planned leave rebar extending 10 cm (4”) up into concrete.


35

If a wood or corrugated metal lintel is planned drive rebar through a hole in the lintel and bend the tip of the rebar over to pin the lintel in place.

REINFORCING EDGES: PIERS Materials: Extra bags and barbed wire

Mur/ Wall: A window or door within 50 cm (19”) of an intersecting wall does not need rebar reinforcement.

Pilier/ Pier: A window or door within 50 cm (19”) of a pier does not need rebar reinforcement.

Ouverture/ Opening: Unreinforced openings must have 1 square meter of wall cross section between them.

In 38 cm (15”) thick walls two openings can be located 50 cm (19”) each side of a pier that is 50 cm (19”) wide and juts out 38 cm (15”) from the wall.

Piers, buttresses, or interior walls must have bags overlapped to connect well to walls. Extend barbed wire from walls into piers and buttress.


36

REINFORCING EDGES: METAL FRAMES Materials: Metal frame, rebar

Cadre/ Frame: Brace a sturdy frame and build bag walls up to it.

Barre/ Rebar: Weld 4- 30 cm (12”) long eyebolts or pieces of rebar to each side of the frame to be located between courses.

Sac/ Bag: Use horizontal braces or additional temporary framework to keep bag ends from bulging past edge of frame when tamped.

Drive vertical rebar pins through eye bolts to secure, or use long staples or bent nails hammered into bags to secure rebar extensions in center of bags.


37

REINFORCING EDGES: WOOD FRAMES Materials: Wood frame, nailer plates

Cadre/ Frame: Build a sturdy wood frame as thick as the bag wall. Add temporary horizontal bracing until tamping is completed. Locate bracing so workers can pass through doorway during construction.

Sac/ Bag: Lay bags up to the frame. Embed nailer plates in bags at edge of opening.

Use 4 nailer plates (see next page) or anchor bolts per doorway side, 2 per window side for small windows, or 3 per side for windows taller than 60 cm (24”).


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ATTACHMENTS: NAILER PLATES Materials: Plywood, small nails, 5x10 cm (2x4 inch)

Sac/ Bag: Keep bags near openings or wall ends tamped firmly.

Fil de fer/ Wire: Continue barbed wire between bag courses and under nailer plate.

Plaque/ Plate: Screw a 30 cm (12”) long piece of 5x10 cm wood (2x4 inch) to one side of a 30 cm (12”) wide piece of plywood or sturdy metal plate. Size the plywood or metal 10 cm (4”) longer than shortest bags at opening.

Clou/ Nail: Tack the nailer well to bags below with 7.5 cm (3”) long galvanized nails. Leave some nails sticking up at least 2.5 cm (1”) above the nailer plate.

Cloutier/ Nailer: Place nailers with 5x10 (2x4) lumber edge exposed.

Screw door or wall frames to 5x10 (2x4) end of nailer plate.

Nailer plates will be covered by rough and finish coats of plaster.


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ATTACHMENTS: ANCHOR BOLTS Materials: Galvanized or painted metal plates, threaded rods

Metal connectors will not be subject to damage by insects or fungus in hot or humid climates. Plaque/ Plate: Place a galvanized or painted metal strap or a plate 6” long with 2 holes between the 2 bags nearest to the opening. Tringle/ Rod: Insert a galvanized or painted bolt or threaded rod through each end of the metal plate. Use a washer and nut to fasten rods to door, window, or wall frame. Fil de fer/ Wire: Lay barbed wire every course to the end of the bag row. Sac/ Bag: Set small end bags between rods. Note: Locate opening so small end bags will not be smaller than 30 cm (12”).


40

ABOUT LINTELS AND ARCHES Openings in earthbag buildings are simpler to build in an earthquake resistant manner if they are limited to 60- 80 cm (24- 31”) width.

A lintel must be sturdy enough to support the weight of the heavy earthbag wall material and the portion of the roof that is supported above the opening. Size lintels for the:

• Length of span

• Weight of wall material and bond beam above

• Proportion of total roof weight resting above the opening

• Live loads on roof and walls

A lintel in an earthbag wall may need to be stronger than a lintel used in a sand-cement CMU wall or a double withe (double thickness) brick wall. Because the walls are thick, the earth in a square face meter (2’ x 5’-5”) of a 38 cm (15”) thick earthbag wall alone can weigh 150- 180 kg (330- 400 pounds) without considering the plaster and wire.

A lintel for a 38 cm (15”) wide wall should be at least 30 cm (12”) wide. Plastering is easier if the lintel is the full width of the wall.

Construction is easier if the total height of the lintel is a multiple of the height of a bag course: 12.5 cm or 25 or 37.5 cm (5 or 10 or 15 inches).

Unless the lintel is to remain exposed from the opening beneath, add mesh to the top of the opening to help the plaster adhere to the upper opening surface.

An arch can be built of unstabilized or cement stabilized earthbags. Arches require rounded forms, a lot of care, and a skilled builder. See other resources for arch design and construction techniques.

In wet climates window sills and door and window jambs can be subject to leaking from wind-driven rain. Overhangs and/ or extended drip edges that protect windows and doors can be helpful. Place door and window frames near the exterior side of walls. Provide sloping exterior window sills of stone or cement or tile. If an earthbag building is finished in earth or earth and lime plaster, use a waterproof gasket above a layer of fired bricks supporting a window sill. If cement plaster is used, metal or reinforced concrete lintels may be best.


41

LINTELS: WOOD FOR DRY CLIMATES Materials: Wood, Plywood, Nails

Cloutier/ Nailer: Nail or screw a plywood or metal nailer plate 75 cm (30”) long to the lintel. Or secure each side with vertical rebar through the lintel.

Linteau/ Lintel: Use solid timber, a built up lumber beam, a laminated beam or box beam, or multiple poles sized for the weight the lintel will carry. Lintel must extend 40 cm (16”) past the opening on each side.

Clou/ Nail: Hammer 7.5 cm (3”) long nails through nailer plate into well-tamped earth-filled bag. Leave several nails sticking 2.5 cm (1 inch) above nailer plate to hold next earthbag in place.

Note: Exposed structural wood may be subject to attack by insects and rot in hot or temperate humid climates. See next page for alternate wood lintel detail for wet climates.


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LINTELS: WOOD FOR HUMID CLIMATES Materials: Wood, plywood, nails, metal flashing, sturdy plasterer’s mesh

Wood structure must be protected against insect attack and rot in hot and humid regions. If cement or metal lintels are not available, encase wood in a generous layer of clay plaster and provide good drip edge to keep it dry. Earth plaster reduces humidity, but cement plaster attracts moisture instead and accelerates wood decay.

Step 1:

Bande/ Strip: Nail or screw a corrugated metal nailer strip 75 cm (30”) long to the lintel.

Linteau/ Lintel: Recess lintel 10 cm (4”) from exterior wall. Use solid timber, a built up lumber beam, a laminated beam or box beam, or multiple poles sized for the weight the lintel will carry. Lintel must extend 40 cm (16”) past the opening on each side.

Solin/ Flashing: Cover lintel with metal flashing that extends past each end and is wide enough to cover the outside edge of the lintel.

Latte/ Mesh: Lay mesh under the lintel and attach to the exterior edge of the bags beneath.

Alternate fastening: place lintel on layer of fired bricks and drive a 1.2m (48”) long rebar through a hole in the lintel on each side of the opening.

Step 2 (Cross-section):

Sac/ Bag: Step earth-filled bags gradually out to meet plane of wall.

Solin/ Flashing: Bend flashing to create drip edge and protect the lintel.

Latte/ Mesh: Fold mesh up and attach to lintel.

Plâtre/ Plaster: Encase exposed wood in fiber-reinforced clay-rich plaster.


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LINTELS: METAL Materials: Wood, plywood, metal

Cadre/ Frame: Hollow rectangular cross-section tubing forms a bond beam in the center of the bag wall.

Barre/ Rebar: Tie the frame to earth-filled bags with 60 cm (24”) long rebar hammered through holes in the frame. Bend end of rebar over.

Linteau/ Lintel: Place more rectangular cross-section tubing next to the bond beam frame. Size the tubing for the span and the weight that the lintel must carry.

Trou/ Hole: Alternate threaded rods extending upward between bags with rebar hammered downward into lower bags through holes every 30 cm (12”).

Clou/ Nail: Drive nails through three holes minimum each side of opening, or bolt lintels to bond beam.

Note: If window sill is lower than bond beam or bond beam is of a different type, use three metal lintel beams of the same length .


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LINTELS: LIGHTWEIGHT CORRUGATED METAL Materials: Corrugated metal strip, angle steel, nails, rebar

For use with 60 cm (24”) maximum width windows placed between roof rafters or under concrete bond beam.

Bande/ Strip: Cut corrugated metal 35 cm (14”) wide.

Cadre/ Frame: Use angle steel of a large enough size to support the courses of bags and bond beam above.

Attache/ Fastener: Bolt or screw metal frames to corrugated strip.

Barre/ Rebar: Pierce corrugated metal with 60 cm (24”) minimum length rebar driven into bags below.

Clou/ Nail: Drive 7.5 cm (3”) long nails through corrugated metal into bags.


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OTHER DETAILS: VENT BLOCK TRANSOM & PANEL Materials: Ventilation blocks (or brick or tile with mortar for openwork), wood or metal lintel, tile or stone sill

Linteau/ Lintel: The lintel is placed above the transom to distribute weight to the bag walls. Ventilation blocks or openwork of brick or tile are not very strong.

Sac/ Bag: In earthbag walls keep openings or vent block panels at least 1m from corners or other openings.

Ouverture/ Opening: For ventilation in hot climates tall and narrow openings work well in earth walls. Panels of vent block allow increased area for ventilation with some horizontal wall reinforcement. A smaller lintel or a separate frame can hold up openwork in the transom above the window because it will not bear the weight of the wall above.

Rebord/ Sill: A sill that extends past the wall surface can reduce rain infiltration somewhat into openings below.

Bloc/ Block: Vent blocks or openwork patterns of tile or brick can callow ventilation but provide security and reduce views in.

Use tarps or screens and/ or curtains inside.


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OTHER DETAILS: WINDOW GRILL Materials: Rebar, nails

Sac/ Bag: Build edges of opening neatly.

Barre/ Rebar: Lay rebar horizontally between bag courses. For added security or if exterior mesh will not be used on walls, pin rebar in place with big staples or with nails placed on the exterior side and bent over.

Ouverture/ Opening: Openings wider than 60 cm (24”) may require vertical grill work as well as horizontal.

Linteau/ Lintel: This is the level of the bottom of the lintel.

A simple way to provide security but allow breezes and light to enter.


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OTHER DETAILS: VENT PIPES Materials: Plastic or metal or tile pipes, clay plaster, optional screens and wire.

Sac/ Bag: Place shorter earth-filled bags between vent pipes.

Pipe/ Pipe: Center pipes above bags. Pipes must be long enough to extend past interior and exterior plaster layers, and protrude 2.5 cm (1”) minimum on exterior.

Dedans/ Interior: The pipes must slope up towards the inside.

Plâtre/ Plaster: Raise the inside of the pipes and fill gaps with the thickened clay plaster that will form the first plaster coat. In humid areas vent pipes near the floor and near the ceiling allow better air

circulation and may reduce mold growth. Vent pipes can have screens fastened around them with wire on the exterior side to prevent animals entering.


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OTHER DETAILS: LIGHT BOTTLES Materials: Glass bottles and jars, clay plaster.

Dedans/ Interior: Place nested bottles or glasses flush with both wall surfaces.

Bouteille/ Bottle: Use larger bottles on the outside and pack with clay-rich plaster to prevent animals or insects nesting in exposed pockets.

Sac/ Bag: Use bottles at bag joints, but do not replace more than 25 cm (10”) length of wall with bottles. Continue barbed wire above and below bottles.

Unless earthbags are stabilized with cement, alternate regular courses of bags with courses that have bottles added.

If more light is desired than ventilation, glass bottles can also be anchored with clay-rich plaster inside a wall opening. Fill the spaces around the bottles with thick fiber-reinforced clayey earth. Use a standard lintel above.

Since the bottles and clay infill are much thinner than the bag walls, a light-filled shelf or niche will result.


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ON THE WALLS Earthbag walls need the right amount of overhang, and the right kind of roof and ring beam.

A continuous ring or bond beam helps to distribute the weight of the roof evenly and to unite earthbag walls during an earthquake. A roof or ceiling that includes a diaphragm of framing and strong sheeting can also provide stiffening and lessen wall motion during an earthquake.

Roofs for earthbag buildings in seismic areas should not add extra outward forces on the tops of the wall. Gable or hip roofs with collar ties or ceiling joists are better than shed roofs.

BOND BEAM: REINFORCED CONCRETE Materials: Cement and sand, wood or metal for forms, rebar, wire, (optional bolts or brackets).

Forme/ Form: Use metal or wood to form for the bond beam 15 cm (6”) high and as wide as the wall. Use temporary braces to support the rebar.

Fil de fer/ Wire: Fasten rebar in place with wire nailed to bags. Overlap rebar 30 cm (12”) minimum at ends and tie well with wire at ends

Barre/ Rebar: 2 rows continuous rebar and hammer 60 cm (24”) long rebar 45 cm (18”) down into bags every 60 cm (24”) minimum

Sac/ Bag: Set earthbags level and tamp well before building the form for the bond beam above

A standard bond beam used on most masonry walls.

Use the right amount of Portland cement in the mix, and don’t add extra water.

Anchor brackets or bolts in concrete, or leave vertical rebar exposed above concrete to attach roof framing.


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BOND BEAM: TUBULAR METAL Materials: threaded rod, hollow rectangular section tube, wood, rebar, brackets.

Sac/ Bag: Set earthbags level and tamp well

Plaque/ Plate: Drill holes in 5x10 cm (2x4 inch) wood top plate every 60 cm (24”) to receive threaded rods.

Tringle/ Rod: Use threaded rod 50 cm (19”) long to sandwich three courses of earthbags between the top plate and the lower metal tube. Align bags to fit between rods.

Barre/ Rebar: Hammer 60 cm (24”) lengths of rebar into bags below through holes in metal tube. Drive in at alternating angles every 60 cm (24”) and bend the tops over.

Métal/ Metal: Drill holes 30 cm (12”) on center in a 1.5x10 cm (1/2”x 4”) piece of hollow rectangular section tube. Lay it flat on the exterior walls 3 courses below the top. Pass galvanized threaded rod through every other hole. Use metal brackets or plates to screw or bolt the metal tubes and the

wood top plates together well at building corners.


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BOND BEAM: CORRUGATED METAL Materials: Corrugated metal, nails, rebar, wood, twine or strapping.

Plaque/ Plate: Use heavy metal bracket or plate to screw wood top plates together firmly.

Barre/ Rebar: Hammer 60 cm (24”) lengths of rebar through holes in wood plate into bags below, punching through corrugated metal strip. Drive in at alternating angles and bend the top over to tie the bond beam to the walls.

Sac/ Bag: Set earthbags level and tamp well

Sangle/ Strap: Use strong cord or strapping or wire with mesh every 60 cm (24”) to sandwich one course of bags beneath the metal strip and two above to the wood top plate.

Bois/ Wood: Drill holes in 5x10 cm (2x4 inch) wood top plate every 60 cm (24”).

Bande/ Strip: Cut pieces of corrugated metal roofing into strips 20- 30 cm (8- 12”) wide. Overlap strips at least 30 cm (12”) and nail to the bag below at overlap points. Lay two courses of earth-filled bags above the corrugated metal strips.


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BOND BEAM: STABILIZED EARTH (FOR ROUND BUILDINGS ONLY) Materials: Tubular bag, cement, rebar, metal for fasteners.

Barre/ Rebar: Before the soil mixture hardens drive 60 cm (24”) lengths of #4 (½”) rebar at alternating angles into the bags beneath. Bend rebar end over and hammer rebar in 60 cm (24”) on center maximum.

Tube/ Tube: Lay earthbag walls level and tamp well. Lay and fill one 30- 38 cm (12- 15”) wide tubular bag 75% full with a mixture of cement-stabilized earth. Place rebar and wire above before bag hardens. Fill a second tubular bag placed on top 75% full with cement stabilized earth.

Attache/ Fastener: Use h-shaped metal fasteners to pin the rebar to the tube beneath, and anchor the bag above well.

Fil de fer/ Barbed Wire: Lay 2 strands of strong barbed wire continuous on top of lower bag.

Barre/ Rebar: Lay 2 lengths of #4 (½”) rebar continuous on top of lower tube. Overlap rebar at least 30 cm (12”) and wire together securely.

Sac/ Bag: Taper earth-filled bags to fit radius and lay level and plumb. Tamp well before adding bond beam.

Test soil to determine minimum amounts of lime and cement required to stabilize.

Provide roof fastening before stabilized soil sets hard. Drive rebar through wood nailer plates, drive long, bent bolts for roof attachment into upper bag, or leave top of rebar exposed to attach brackets for fastening roof.


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EAVES WIDTHS AND PLASTER CHOICES Earthen plasters on exterior walls are very durable in dry climates. In dry areas buildings can have narrow roof overhangs, or domed or vaulted roofs without any overhang at all.

In areas where it rains more often, at least a 30 cm (12 inch) minimum roof overhang will lead rain away from the bases of walls.

Clay resists water better than cement plaster if it can dry between soakings. Clay swells in contact with water and seals the pores of the plaster surface more tightly. But clay plasters and the wall underneath must dry thoroughly between soakings or they will start to erode. In hot regions with stronger sunlight, walls will dry more quickly than in temperate regions. Walls that face the sun will also dry out more quickly.

Eaves widths are often chosen based on local traditions and building styles shaped by the climate. Many tropical buildings rely on wide eaves to shade and cool verandahs and building walls. But narrow eaves may be desired to reduce lift from high winds. In temperate areas, narrower eaves let low winter sun in to warm the building. It may be wisest to select eaves widths first and then investigate whether clay plasters will need extra protection in your climate with the preferred eaves widths.

Many people assume they will put cement stucco on an earth building. Cement is too stiff to use on earthbags made with heavy clay soils because cement will crack when the underlying clays expand and contract. Cement also attracts humidity and prevents the clay wall materials from drying. Cement plasters added on the exteriors of older adobe buildings often cause serious damage.

Earth plasters can be stabilized with lime. This type of plaster can be used on bags filled with most types of soils. In some areas special craftsmen make and age lime plaster to sell.

In frost-free regions cement-stabilized plasters can be more safely used than in cooler regions. They are best kept off of bags filled with very heavy clay soils. But in tropical regions cement plasters should last well on bags filled with lighter soil mixes that contain less than 12- 15% clay.

In temperate regions cement plasters can be used on bags filled with gravel or sand. These will need to be braced well until a sturdy cement stucco combined with mesh can be completed.

If you need to use a clay plaster, it can be protected in different ways. The lower sections of exterior walls often need more protection from rain and splashing water than the upper portions. In some places exterior earth plasters are finished with aggregate layers of pebbles or mosaics that resist erosion. Tile or stone veneer can also be inset into clay plasters and grouted with cement. Some types of clays can be made more resistant to cycles of wetting by the addition of natural materials like milk, blood, or urine, or of chemical additives like sodium silicate. Traditional craftsmen may have good advice about choosing soils and additives for durable plasters.


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NEW ZEALAND’S OVERHANG REQUIREMENTS FOR A VERY HUMID, TEMPERATE REGION:

RATIO WALL HEIGHT WALL HEIGHT WIND CONDITIONS WALL HEIGHT: EAVES 2.4 M (7’10”) 3.0 M (9’10”) Low wind (32 m/ sec.): Cities, subdivisions, farm near a hedge 4:1 60 cm (24”) eaves 75 cm (30”) eaves Medium wind (37 m/ sec.): Farmland with some scattered trees 8:3 90 cm (36”) eaves 1.13 m (45”) porch High wind (44 m/ sec.): Large fields and pastures, near beaches 3:2 1.6 m (5’3”) porch 2.0 m (6’6”) porch

High wind but wall faces the sun 2:1 1.2 m (4’) porch 1.5 m (5’) porch

New Zealand is a temperate country that includes very humid areas. Queensland has freezing ground 7 months of the year, and a very high average humidity of 76%. It rains 900 mm average per year, and only receives 1900 hours of sunshine per year.

The New Zealand code for earth buildings includes ratios for wall height to eaves width that they feel are wise to protect un-stabilized clay plasters. Wider eaves are required in windier locations. Wide eaves can be created by porch roofs with separate supports, or clay plaster can be reserved for interior walls.

Building codes are written to protect building officials from liability. Builders who regularly use earth plasters on exterior walls can give you the best advice about where to use which plasters. If you need to plan for a building without a local expert, how much protection is enough? Compare climates to evaluate how difficult conditions are for exposed earth plasters. Regions with frost will keep clay surfaces soggy longer. Humid regions with fewer hours of sunshine will not let walls dry out very often. Although Port au Prince, Haiti receives more rain than Queensland, it has no frost, a lower average humidity (49%), and receives 150% as much sunshine every year. If earth plasters are able to dry out twice as quickly as they do in Queensland, NZ, approximately half as much roof overhang may be needed to protect earth buildings. The following chart is a wild guess, but provided to give some perspective on the issue of clay plaster durability.

50% LESS OVERHANG FOR A MODERATELY RAINY TROPICAL REGION:

WIND CONDITIONS WALL HEIGHT: EAVES 2.4 M (7’10”) 3.0 M (9’10”) Low wind (32 m/ sec.): Cities, subdivisions, farm near a hedge 8:1 30 cm (12”) eaves 35 cm (14”) eaves Medium wind (37 m/ sec.): Farmland with some scattered trees 5:1 50 cm (20”) eaves 60 cm (24”) eaves High wind (44 m/ sec.): Large fields and pastures, near beaches 3:1 80 cm (31”) eaves 1 m (39”) eaves

High wind but wall faces the sun 4:1 60 cm (24”) eaves 75 cm (30”) eaves

build to resist hazards/ construire pour résister aux dangers

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