Earthbag construction is a building method that uses stacked bags filled with soil or other mineral materials to create walls. The technique has gained popularity as a low-cost, low-impact building method suitable for owner-builders. Earthbag walls are strong, fire-resistant, and provide excellent thermal mass. The method is particularly well-suited to climates with large diurnal temperature swings, where the thermal mass of the walls moderates indoor temperatures.
The primary materials are polypropylene bags or tubes, typically 45 to 60 centimeters (18 to 24 inches) wide, and soil. The ideal soil for bag filling is a mix of 70 percent sand and 30 percent clay, which compacts to a stable, durable mass. Purely sandy soil may not bind adequately, while high-clay soil can shrink and crack. The soil is slightly moistened before filling to aid compaction. Each bag is filled to approximately 80 percent capacity, allowing the material to be tamped into a solid block.
The wall is built course by course, with each bag laid in a running bond pattern similar to brickwork. Between each course, two strands of four-point barbed wire are laid to prevent the bags from slipping and to provide tensile reinforcement. The bags are compacted with hand tampers, and the wall's alignment is checked with a level and line after each course. Openings for doors and windows are framed with wood or reinforced Concrete Foundation. The walls are typically stuccoed or plastered with a cement, lime, or earthen plaster for weather protection.
Earthbag construction is used for homes, garden walls, greenhouses, and small outbuildings. The walls can be built straight or curved, allowing for round or domed structures. A 30 centimeter (12 inch) thick earthbag wall provides a thermal mass equivalent to 30 centimeters of concrete. The method requires no specialized skills and can be learned by most builders in a few days. Cordwood Masonry and Timber Framing framing are complementary building methods for different parts of a homestead.