Editing Earth shelter (section)

===Building materials===
The selection of construction materials should consider the type of structure, site characteristics, climate, soil type, and design. Stronger, longer-lasting building materials are required for structures that are buried deeply. Waterproof and insulated materials should also be utilized to withstand the pressure and moisture of the surrounding ground. For instance, concrete and reinforced masonry, wood, and steel are all viable materials. Concrete is the most common choice for earth-sheltered buildings due to its strength, durability, and fire resistance. Cast-in-place concrete is employed for non-critical structural elements such as concrete foundations, floor slabs, and exterior walls with less than {{convert|6|ft|m|abbr=off|sp=us}} of earth cover. In contrast, precast reinforced concrete can be used for floors, walls, and roofs. Concrete masonry units should be {{convert|8|in|mm|abbr=off|sp=us}} or greater, with the use of “A” or “H” facilitating unit placement around vertical reinforcing bars, depending on the required structural integrity. It is typically advised to use Type S mortar, grout with a minimum strength of {{convert|2,000|psi|MPa|abbr=on}}, and a concrete slab with a minimum strength of {{convert|2,500|psi|MPa|abbr=on}} and {{convert|4|in|mm}} thickness.<ref>{{cite web|last1=NREL / DOE |title="Earth-Sheltered Houses" |url=https://www.nrel.gov/docs/legosti/fy97/6993.pdf |access-date=15 November 2022}}</ref> Brick or stone masonry reinforced with steel bars can be utilized for walls that will be subjected to lateral or vertical pressure from earth cover. Masonry generally costs less than cast-in-place concrete. Wood can be widely employed in earth-sheltered buildings for structural and internal work, including floors, roofs, and exterior walls. However, wooden frame walls, which must endure lateral pressure, are limited to a burial depth of one story when used as a structural material. Beyond this depth, the cost will rapidly increase while using wood as a structural material. Although wood can be less expensive than other materials, it lacks steel's strength, therefore it might not be the ideal option for structural material in some earth-sheltered dwellings, especially in moist soil type. Steel is used for beams, columns, bar joists, and masonry reinforcement. The advantage is that steel has high tensional and compressional strength, while the disadvantage is that it must be protected from corrosion if it is exposed to air, water, or other chemicals. It must be used effectively because it is also expensive.<ref>{{cite web |title="Earth-Sheltered Buildings" |url=https://ncma.org/resource/earth-sheltered-buildings/ |publisher=NCMA |access-date=15 November 2022}}</ref>