Cob (material)

Cob, cobb, or clom (in Wales) is a natural building material made from subsoil, water, fibrous organic material (typically straw), and sometimes lime.^[1] The contents of subsoil vary, and if it does not contain the right mixture, it can be modified with sand or clay. Cob is fireproof, termite proof, resistant to seismic activity,^[2] and uses low-cost materials, although it is very labour intensive. It can be used to create artistic and sculptural forms, and its use has been revived in recent years by the natural building and sustainability movements.

In technical building and engineering documents, such as the Uniform Building Code of the western USA, cob may be referred to as "unburned clay masonry," when used in a structural context. It may also be referred to as "aggregate" in non-structural contexts, such as "clay and sand aggregate," or more simply "organic aggregate," such as where cob is a filler between post and beam construction.