Earthbag construction

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Earthbag construction is a very inexpensive method of construction that is very strong and can be built very quickly. It is a natural building technique that has evolved from historic military bunker construction techniques, and temporary flood-control dike building methods. The technique requires only very basic construction materials: earthbag sacks or tubes (see Superadobe), filler materials based on inorganic soils available on site, such as sand, gravel, clay or crushed volcanic rock. Barbed wire is placed between each row of bags, and sometimes twine is wrapped around the bags, which serves to hold the structure together and add strength. The construction technique can be used for emergency shelters, temporary housing, barns or almost any conceivable long-term structure.

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[edit] Nader Khalili

Architect and builder Nader Khalili is one of the pioneers whom has helped develop and popularize earthbag construction and Superadobe. He is closely associated with many aesthetic designs, building techniques, and proposed innovative uses. Several books and videos have been produced to demonstrate the method, and a number of individuals and groups offer training workshops.


[edit] Construction Method

The basic construction method begins by digging a trench down to undisturbed mineral subsoil. In this is placed a foundation, consisting of a row of woven bags or tubes, filled with the material of choice. On top of these, one or more strands of four-pronged barbed wire are placed, which dig into the bag's weave and prevent slippage between it and subsequent bag rows or layers. On top of the barbed layer, the next row of bags (or tube) is placed, either to be prefilled with material and hoisted up, or filled "in place", particularly for the tube style "Superadobe". The weight of this earth/sand-filled bag pushes down on the barbed wire strands, locking the bag in place on the row below. The same process continues layer upon layer, to form walls.

[edit] Bag Types

The most popular type of bag is made of woven polypropylene, such as the type often used to transport rice. Polypropylene is chosen for its resistance to water damage, rot and insects, and its low cost. Some of the organic/natural material advocates prefer hemp, burlap or other natural-fiber bags, like "gunny sacks".

[edit] Filler Materials

Almost any inorganic material can be used as filler material.

Thermal insulation is an important consideration, particularly for climates that experience temperature extremes. The thermal insulating value of a material is directly related to the porosity of the material and the thickness of the wall. Crushed volcanic rock, pumice or rice-hulls, yield higher insulation value than clay or sand.

[edit] Roofing

Various methods of roofs may be used, including earthbag extensions of the wall which create barrel vaulted or domed roofs. Windows and doors are typically formed in with corbeling or brick-arch techniques, sometimes on temporary forms, or with a lintel supporting the top. Light may be brought in by glass-capped pipes or salvaged bottles which are placed between the rows of bags during construction.

[edit] Finishing

To prevent UV damage to the fabric, it is necessary to cover the outer surfaces of the exposed bags with an opaque material. There are many possible choices for this material, including stucco or plaster. Waterproofing is also needed for non-vertical elements, in all but the driest climates, and can be accomplished by additives to the bag-fill material, the stucco or as an added layer on the outer surface. Some designers/builders use a planted-earth "living roof" ("green-roof") to top the structure, or more conventional framing and roof finishes may be placed atop earth-bag walls.


[edit] Colonization of the Moon

Mr. Khalili has proposed the use of earthbag construction for structures on the Moon. Currently, it is extremely expensive to launch a payload from earth. So this would be an ideal solution, because the bulk of the cargo would consist of lightweight bags and some tools to fill the bags. The bags would have pre-sewn "hook and loop" (i.e. Velcro) fastener strips in lieu of barbed wire. The bags would be filled with moon-dust (powdered pumice).

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