Earthbag construction

Earthbag Construction Basics and Techniques
– Earthbag is a natural building technique derived from military bunker construction and flood-control dike building methods.
– It requires basic construction materials such as sturdy sacks filled with organic material.
– The walls are built by laying the bags in courses, forming a staggered pattern.
– Earthbag walls can be curved or straight, and can be topped with conventional roofs.
– International standards for bracing walls and seismic risk areas exist.
– Standard earthbag fill materials include moist subsoil with enough clay or water-resistant angular gravel.
– Walls can be curved or straight, providing good lateral stability.
– Barbed wire is used between courses to improve friction and tensile strength.
– Rebar can be hammered into walls to strengthen corners and opening edges.
– The structure is typically finished with plaster to shed water and prevent UV damage.
– Construction often begins with a trench filled with stones and/or gravel for a rubble trench foundation.
– In high seismic risk regions, a reinforced concrete footing or grade beam may be recommended.
– Bags filled with gravel form a water-resistant foundation with barbed wire on top.
– Bags are offset in each course and can be pre-filled or filled in place.
– The weight of the fill material locks the bags in place, and tamping consolidates the moist clay-containing fill.
– A roof can be formed by gradually sloping the walls inward to construct a dome.
– Vaulted roofs can be built on forms, or a bond beam is used under a traditional roof type.
– Hip roofs, gable-type trusses, or vigas may be needed to reduce outward stress on earthen walls.
– Windows and doors can be formed with a traditional lintel or with temporary forms.
– Light can be brought in by skylights, glass-capped pipes, or bottles placed between bag courses.
– Walls should be covered with cement-based stucco, lime, or earthen plaster to protect the bags from UV rays or moisture.
– Infill plaster of earth with straw is used to fill the nooks between bags or courses.
– Roof overhangs reduce plaster waterproofing requirements.
– Some buildings use a planted-earth living roof (green-roof) or a conventional framing and roof placed atop earthbag walls.
– Buildings last a long time when maintained properly.

Key Figures in Earthbag Construction
– Paulina Wojciechowska wrote the first book on earthbag building in 2001.
– Kelly Hart developed a massive online database of earthbag information.
– Kaki Hunter and Doni Kiffmeyer worked on various projects after studying with Khalili.
– Owen Geiger and Patti Stouter have developed free online booklets on earthbag construction.
– Owen Geiger’s e-book provides step-by-step illustrations and discussions of new techniques.
– Akio Inoue from Tenri University and Scott Howard of Earthen Hand have tested and built earthbag buildings.
– Robert Shear built an earthship-inspired earthbag house in Utah.
– Nader Khalili reintroduced earthbag construction as superadobe for humanitarian efforts.
– Dr. John Anderton of South Africa tested a triple channel bag version and developed a narrow wall contained sand system.
– Fernando Pacheco of Brazil pioneered the use of lighter HDPE mesh tubing for hyperadobe walls.

Terminology and Materials
– Earthbag is a varied family of techniques with different strength and reinforcement requirements.
– Contained earth (CE) is the original technique with specific soil strengths and reinforcement chosen for hazard levels.
– CE uses damp, cohesive, tamped bag fill that bonds strongly with reinforcement as the wall cures.
– Contained sand (CS) uses sand fill or any fill too dry or with poor cohesion that performs like sandbags.
– Contained gravel (CG) uses fill of any aggregate larger than coarse sand.
– Inorganic material is generally used as filler, but some organic material can be used with reinforcement.
– Earthen fill may contain clay and can be reject fines, road base, engineered fill, or local subsoil.
– Soil fill can contain a high proportion of aggregate, as long as it tamps and cures strongly.
– Sands, stone dust, and gravels can survive prolonged flood conditions but require special bracing during construction.
– Stabilization with cement, lime, or bitumen allows clay soil to withstand flooding or sands to be used with a non-structural plaster skin.

Reinforcement and Structural Performance
– Solid CE may require less barbed wire in low-risk areas as walls solidify between courses.
– Earthbag with barbed wire is more flexible than adobe and may resist collapse when detailed carefully.
– Earthbag of weak soil without steel is half the shear strength of unreinforced adobe.
– Domes tested in California resisted approximately 1 g forces due to their stable shape.
– Special reinforcement is needed for earthbag walls to resist higher forces.

Applications and Environmental Considerations
– Earthbag building techniques used in Sri Lanka after the 2004 tsunami.
– Multiple earthbag construction projects completed in Haiti after the earthquake.
– First Steps Himalaya and other charities built over 50 earthbag buildings in Nepal before the 2015 earthquake.
– Local builders in Nepal received earthbag training after the earthquake.
– International NPOs built hundreds of earthbag buildings in Nepal.
– Khalili proposed using earthbag construction techniques for building structures on the Moon and other planets.
– Earthbag construction could be a cost-effective solution for lifting supplies to space.
– Lightweight bags and a few tools would be the main supplies needed for earthbag construction in space.
– Pre-sewn hook and loop fastener strips could replace barbed wire in space construction.
– Earthbag construction uses very little energy compared to other durable construction methods.
– 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.
– The energy-intensive materials used, such as plastic, steel wire, and plaster, are used in relatively small quantities.
– Buildings last Source:  https://en.wikipedia.org/wiki/Earthbag_construction