Earthbag construction
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Earthbag construction is a very strong, very cheap way of creating structures. It is an alternative-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: sacks, filler material such as sand or gravel, barbed wire (using the barbs on the wire as well as the wire for reinforcing). This system allows for rapidly and inexpensively constructing temporary or emergency shelters or for long-term structures in milder climates.
Nader Khalili is one of the pioneers most associated with this approach. Several books and videos have been published/produced demonstrating if and a number of individuals and groups offer workshops on it.
The basic idea is that one starts by digging a trench down to undisturbed mineral subsoil. In this is placed a first row of woven bags or tubes (usually woven polypropylene, but some of the organic/natural material advocates prefer hemp, burlap or other natural-fiber bags, like "gunny sacks"), filled with gravel, sand or crushed volcanic rock. On top of these, one or more strands of four-pronged barbed wire are placed, which dig into the bag's weave and prevent sippage 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 filled "in place" with sand or on-site earth, or prefilled with the same. The weight of this earth/sand-filled bag pushes it down onto the barbed wire strands, locking it in place on the bag-row below. The materials cost for earthbag buildings is very low.
The same process continues layer upon layer, to form walls or even up to the top of resultant 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. Or light may be brought in by placing glass-capped pipes or salvaged bottles between rows.
For finishing, it's necessary to stucco or plaster the bag surfaces, to prevent UV damage to the fabric. Water-proofing is also needed for non-vertical elements, in any but the driest climates, and can be accomplished by additives to the bag-fill material, the stucco or as an added layer on the 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.
Mr. Khalili has even proposed its use for structures on the Moon, in which case only the bags would be transported from Earth (with pre-sewn-on velcro strips in lieu of barbed wire), and then filled with moon-dust (powdered pumice). An alternative that offers far greater insulation values than earth, for harsher climates on our "home planet", is to substitute pumice or rice-hulls for the earth or sand fill.
[edit] See also
[edit] External links
- The Natural Building Network - Find natural builders, teachers and resources.
- Green Home Building
- Cal-Earth - The California Institute of Earth Art and Architecture has developed a patented system called Superadobe, in which bags filled with stabilized earth are layered with strands of barbed wire to form a structure strong enough to withstand earthquakes, fire and flood.
- Earth Hands and Houses building with earthbag in Poland
