by Steve Graham, Networx
Cob construction is like shaping a house with artists’ clay but never baking it. Cob (which borrows an Old English word for mound and has nothing to do with corn) is a mass of straw, clay, sand, and water. In a gradually reviving form of construction, it is hand-sculpted into buildings while the mixture is still wet.
Cob construction may be the world’s most environmentally friendly building process. There are no additives or chemicals. No energy is consumed in heating or forming the material, and no heavy machinery is required. In the right areas, the basic building materials all can be obtained locally.
Cob was used for many years in Europe, and is still widely used in Africa. Many European earth structures are still standing despite centuries of rain and harsh winters.
It is closely related to adobe, a popular building style in the Southwestern United States. The main difference is bricks. Adobe uses sun-dried earth bricks connected with mud mortar. Cob construction is a simpler concept, but takes detailed planning. Here are the first steps of cob construction.
Choosing a Site
The most important factor is drainage. Cob will break down if it is submerged. Make sure that even a 1,000-year flood won’t saturate your cob walls.
Instead, build on a hill to ensure good drainage. Cob works well on sloped properties that complicate standard frame construction. Also look for full sun exposure in the winter, and land with available clay soils, if possible.