Editing Earth shelter (section)

===Walls===
Several different methods of external ([[Load-bearing wall|load-bearing]]) wall construction in earth shelters have been used successfully. These include [[Concrete masonry unit|concrete block]] (either conventionally [[Mortar (masonry)|mortared]] or surface-bonded), [[Masonry#Stonework|stone masonry]], [[Cordwood construction|cordwood masonry]], poured concrete, and [[Wood preservation#Pressure processes|pressure-treated wood]].<ref name="roy2006" /> Earthships classically use rammed earth tire walls, which are labor-intensive but recycle used tires.<ref name="roy2006" />

Oehler prescribed a very low budget method he termed "post, shoring and polyethylene". This involves buried wooden posts to act as a frame, shored up with planks, and with a [[Vapor barrier|waterproofing barrier]] of polyethylene sheet between the planks and the backfill, but no foundation and nothing on the floor except a plastic sheet and carpeting.<ref name="oehler1981" />

Untreated wood in direct contact with earth rots within five years of use in earth shelter construction, but can be used for structural support construction in a well-insulated and water/moisture-proofed home. Reinforced concrete is the most commonly used structural material in earth shelter construction. It is strong and readily available. Steel can be used but needs to be encased by concrete to keep it from direct contact with the soil which corrodes the metal. Bricks and concrete masonry units are also possible options in earth shelter construction but must be reinforced to keep them from shifting under vertical pressure unless the building is constructed with arches and vaults.

Unfortunately, reinforced concrete is not the most environmentally sustainable material. The concrete industry is working to develop products that are more environmentally friendly in response to consumer demands. Products like [[Grancrete]] and [[Hycrete]] are becoming more readily available. They claim to be environmentally friendly and either reduce or eliminate the need for additional waterproofing. However, these have not been extensively used in earth shelter construction yet.