Natural building means sustainable building at its “greenest.”
Natural building utilizes minimally processed, nontoxic materials and systems used appropriately for the climate, site and intended use. It incorporates primarily natural materials rather than high embodied energy, processed commercial materials, with a focus on getting these natural materials from as local a source as possible–ideally, from the building site itself.
Natural Building Techniques:
“Cob” is an old English term meaning loaf or lump. Cob construction uses a mixture of clay, sand and straw, and is used mostly in a structural, or load-bearing, capacity as house and building walls. But it is an extremely versatile medium that can be used for garden walls, benches, bas relief, bread ovens, and more. Building with cob is like building a big clay pot, as it requires no formwork or preforming in to blocks. It is magnificently sculptural and lends itself well to curvilinear and freeform walls and artistic expression. The high thermal mass of cob helps reduce temperature swings by storing and releasing heat, and the clay can help control humidity – beneficial properties in Central Texas and elsewhere.
Houses made of bales of straw can be load bearing (carrying the load of the roof) or they can used to create the walls (infill) of a post and beam structure. Walls are generally plastered with lime on the exterior and earth on the interior, but other finish options are possible as well. The thick walls created by the 18″ thick bales (most Texas bales) not only provide phenomenal insulation (about R-43) but give a look of solidity and lovely thick-wall aesthetic at window and door openings. Appropriately designed and constructed straw bale buildings do well in nearly all climates, including hot and humid Central Texas.
Light clay straw walls are made by tossing loose straw with clay slip, then lightly packing the mixture into slip forms. It is a non-loadbearing material placed as infill between columns and intermediate supporting structure such as timber frame or steel. Light clay straw walls offer both insulative and thermal mass properties, with the balance depending upon the ratio of clay to straw. It can be used as perimeter walls or interior walls (even between 2×4 wood studs) and typically receives coatings of lime or earthen plaster.
Earthbag construction is a relatively quick process that uses woven polypropylene feed bags filled with clayey or sandy soil, sand or gravel to form foundations, walls, benches, and more. Beautiful curvey forms and domes can be created using earthbags.
Beautiful, thick, solid earthen walls can be created by ramming slightly moistened earth in sturdy forms. The resulting walls can be finished with a clear sealer to reveal the earthen stiations, or plastered with lime or earth plaster. Colored clays or artifacts such as geodes and fossils can be cast into rammed earth walls for added interest. Rammed earth walls are load-bearing and offer very high thermal mass but low insulating properties.
Compressed Earth Block
Slightly moistened earth is compressed under great pressure in to blocks that are immediately ready to put into the wall. Compressed earth blocks (CEB) can be used to form perimeter or interior load bearing walls or can be used for infill within another, structural system. These versatile blocks have been successfully used in both residential and commercial construction, and their familiar shape and method of laying can make acceptance in the conventional construction world more likely.
Several books and websites with information on natural building materials and systems are shown in our Resources section – see Print & Web Resources.
For another introduction to various natural wall systems, see a Comparison of Natural Building Techniques, a partial list of wall systems and properties by Michael G. Smith on the website of the Natural Building Network.
Rubble Trench Foundations
Natural Swimming Pools