Natural building means building with natural materials.
In most definitions, nautral building materials include:
- earth (the sand, clay, and silts in soils)
- fibre (straw, manure, or wood fibers
- Oil and crystaline finishes
These materials can combine to make an entire house, or can be mixed with a limited amount artificial materials to ease the process of construction.
Natural building styles include:
- Wattle and daub
- Light-clay straw
Cob is a mix of Sand, Clay, and Straw. This is an incredibly accessible technology–with these three materials a huge variety of sculptural and building forms can be easily made. The sand provides compression strength, the clay provides grain-scale tensile strength, and the straw provides wall-scale tensile strength. Compare to Sand, Cement, and Rebar: Sand provides compression strength, cement binds on a grain level, and rebar provides tensile strength. Cob’s advantages are high thermal mass, ease of use, lack of toxicity, sculptural fun, fireproofness, bug-proofness, low sound transmission. Cob’s limitations include below-ground application, inabilty to endure chronic moisture. It also has low R-value: heat passes through.
Wattle and daub is a mix of young sapling bows and earthen materials. It makes a thinner wall than is possible with cob–great for building shells or interior walls.
Strawbale is a technique using waste-products from wheat production. What a great re-use of a waste product. Straw has extremely low thermal conductivity as well as enough structural (compressive) strength to support a roof. Sheathed in natural plasters strawbale houses can perform better than most artificial materials for thermal resistance, sound impermiability, quality indoor air.
Clay-straw is a great infill material for post-and beam wooden structures. Health benefits of cob and strawbale are prevalent, but does not have compressive strength.
Log: logs are a great tradition. Cabins from Lincoln to today are still performing well. Their ability to make cornerless buildings is limited.
Cordwood is a mix of cob and log building–with short, firewood length logs. Good thermal mass and insulation, soundproof, durable, easy to build. Less flexible and massive than cob but more insulative. Less insulative than Strawbale, but more mass.