Earthbag construction is relatively low cost method to build structures which can be built quickly and are strong. It is a building technique which evolved from the historic military bunker construction and temporary flood control.
Earthbag technology requires very basic construction techniques, mainly strong sacks filled with inorganic material, subsoil. Sometimes instead of sacks, long tubes are used. The range of the fill can be anything from clay to pure sand and can also be gravel or crushed volcanic rock, but usually the bags are filled with subsoil that contains some clay to form a rammed earth type of consistency inside the bags. The way the walls are built and detailed greatly will depend on what the fill of the bag is, and what type of climatic condition, i.e. whether the area is prone to earthquake or flooding.
The bags or tubes are filled on site, the fill being brought to the bags. Usually the cheapest bags available are made out of polypropylene, although burlap or hessian bags can be found, or they can be made out of any material that doesn’t stretch too much. To improve on friction between the courses and tensile strength barbed wire is used. If the structure is not in an earthquake zone, and barbed wire wants to be avoided, then the wall can be pegged if designed appropriately.
Its important for the structure to be finished with a plaster or a render as the UV from the sun will deteriorate the polypropylene bags within a few months.
As well as vertical straight walls, Earthbag structures can be built as domes with arched openings therefore used in areas where there is no wood or clay. The main structural reason that Earthbag domes can be built is due to corbelling. This means each row of bags is inset slightly from the course below. Corbelled domes made of adobe and stone have been built for thousands of years. The concept has been applied to earthbags in the last few decades initiated by Nader Khalili who largely developed and popularized the methods and arch