Cob (building)

Cob, cobb or clom (in Wales) is a natural building material made from subsoil, water, some kind of fibrous organic material (typically straw), and sometimes lime. The contents of subsoil naturally vary, and if it does not contain the right mixture it can be modified with sand or clay. Cob is fireproof, resistant to seismic activity, and inexpensive. It can be used to create artistic, 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, cob may be referred to as an "unburned clay masonry" when used in a structural context. It might also be referred to as an "aggregate" in non-structural contexts, such as a "clay and sand aggregate" or more simply an "organic aggregate," such as where the cob is an insulating filler between post and beam construction.

Cob is an English term attested to around the year 1600 for an ancient building material that has been used for building since prehistoric times. The etymology of cob and cobbing is unclear, but in several senses means to beat or strike, which is how cob material is applied to a wall.

Some of the oldest man-made structures in Afghanistan are composed of rammed earth and cob. Cobwork (tabya) was used in the Maghreb and al-Andalus in the 11th and 12th centuries, and was described in detail by Ibn Khaldun in the 14th century.

Cob material is known by many names including adobe,lump clay,puddled clay, chalk mud,wichert,clay daubins,swish (Asante Twi),torchis (French),bauge (French),bousille (French mud with moss), and cat and clay.

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