Earthbag Homes

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 (offset by half a bag width to form a staggered pattern), 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. A roof can be formed by gradually sloping the upper walls inward to form a dome, or traditional types of roof construction may be used instead.

The most popular type of bag is made of woven polypropylene, such as the type often used to transport rice or other grains. Indeed many used grain bags are reused as earthbags. 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"; however, these will rot if not kept perfectly dry.

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 both the porosity of the material and the thickness of the wall. Crushed volcanic rock, pumice or rice-hulls (see Rice-hull bagwall construction), yield higher insulation value than clay or sand.

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. The addition of lintels allows square windows to be used.

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, plaster or adobe. Waterproofing is also needed for non-vertical elements, in all but the driest climates, and can be accomplished by using additives in the bag-fill material, or in 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.