Earth Bag Structure
Earthbag building uses polypropylene rice bags or feed bags filled with soil or insulation that are stacked like masonry and tamped flat. Barbed wire between courses keeps bags from slipping. Earthbag construction is a low-cost construction technology that uses primarily local dirt to produce structures that are both sturdy and rapid to construct. It’s a natural construction approach that evolved from past military bunker construction methods and temporary flood-control dike construction methods. The approach calls for only the most basic building materials: strong bags filled with organic stuff.
Standard earthbag fill material has internal stability. Either moist subsoil that contains enough clay to become cohesive when tamped, or a water-resistant angular gravel or crushed volcanic rock is used. Walls are gradually built up by laying the bags in courses-forming a staggered pattern similar to bricklaying
The walls can be curved or straight, domed with earth or topped with conventional roofs. Curved walls provide good lateral stability, forming round rooms and/or domed ceilings like an igloo. The structure is typically finished with plaster, either cement stucco on a strong mesh layer or an adobe or lime plaster, to shed water and prevent fabric UV damage.
Environment Friendly Technique
Earthbag construction uses very little energy compared to other durable construction methods. Unlike concrete, brick or wood, no energy is needed to produce the earthen fill other than gathering soil. If on-site soil is used, little energy is needed for transportation. Unlike rammed earth construction, only human labor energy is required to tamp the soil lightly. The energy-intensive materials that are used – plastic (for bags & twine), steel wire, and perhaps the outer shell of plaster or stucco – are used in relatively small quantities compared to other types of construction, often totaling less than 5% of the building materials. Buildings last a long time when maintained. However, if “raw” or un stabilized soil is used as fill, when the building is no longer useful the earthen fill can be recycled into either garden areas, backfill, or new earthen buildings.
Use in Disaster Areas
Earthbag building techniques were also explored in Sri Lanka after the 2004 tsunami. Multiple earthbag construction projects have been completed in Haiti, most of these after the earthquake. First Steps Himalaya and other charities had built more than 50 earthbag buildings in Nepal prior to the April 2015 earthquake. Since then, local builders flocked to ongoing earthbag training opportunities, including those by Good Earth Global, which have led to official Nepal building code acceptance of this technique for residences. International NPOs have built hundreds of contained earth or earthbag buildings in Nepal as well, more residences than larger clinics or schools. NPOS are asking for more structural information to be better able to choose reinforcement types and intensity appropriate to local soil strength and seismic risk. University testing has begun but more is needed.