Earthbag construction

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 long tube-shaped bags, see Superadobe), filler materials based on inorganic soils available on site, such as sand, gravel, clay or crushed volcanic rock. Walls, are built up by laying the bags in courses, forming a staggered pattern much like bricklaying. The walls are almost always curved, mainly to provide improved lateral stability, thus forming round rooms and domed ceilings (like an igloo). (The curved structures also enable efficient use of materials, and energy efficient buildings.) To improve rigidity between each row of bags, barbed wire is placed between the courses, and sometimes twine is wrapped around the bags to tie one course to the next, which serves to hold the structure together and add strength. The structure is typically finished with plaster, stucco or adobe to shed water and to protect the bags from UV rays. The construction technique can be used for emergency shelters, temporary housing, barns or almost any conceivable long-term structure.

Nader Khalili

Architect and builder Nader Khalili is one of the pioneers whom has helped develop the construction methods and architecture, and has popularized earthbag construction and Superadobe, particularly for residential buildings. 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.

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 (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.

Bag Types

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.

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 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.

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

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, 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.

Green building

Earthbag construction arguably uses the least energy of any other durable construction method. Unlike concrete, brick or wood, no energy is needed to produce the filler material, other than for digging the soil out of the ground. When on-site soil is used, no energy is used in transportation of materials. Unlike rammed-earth construction, no additional energy is needed to compact the soil. The energy intensive materials that are used, including plastic (bags & twine), steel (wire), and plaster, are used in very low quantity compared to most other types of construction. The buildings can last a long time, and can either be recycled or allowed to erode without causing damage to the environment because no harmful substances are used.

Colonization of the Moon

Mr. Khalili has proposed the use of earthbag construction for structures on the Moon or other planets. 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).

ee also

* Rice-hull bagwall construction
* Green Roofs
* Natural building
* Super Adobe

External links

* [http://www.earthbagbuilding.com EarthbagBuilding.com] - Sharing information and promoting earthbag building.
* [http://www.grisb.org Geiger Research Institute of Sustainable Building] - Promoting natural building, and sustainable design and development, through research, training, education and consulting services.
* [http://www.calearth.org 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.
* [http://www.earthhandsandhouses.org Earth Hands and Houses building with earthbag in Poland]
* [http://www.archearth.com ARCHEARTH DESIGN] : SOUND TEMPLE Koh Phangan Thailand, "'DOME in Portland Oregon