Cob is a building material. It consists of a mixture of clay, sand and
straw.
Cob-building is a traditional technique that has been used for
thousands of years and in all kind of climates (cob houses can be found
in Africa as well as in Wales). However, in the U.K. it is most
strongly associated with counties of Devon and Cornwall, where many cob
cottages have survived and are still lived in. The walls of a cob house
are necessarily thick, and windows are correspondingly deepset, giving
the houses a characteristic internal appearance.
The thick walls also provide excellent thermal mass, so that, depending
on the climate, cob cottages are relatively easy to keep warm in
winter, and tend to be cool in summer. Surprisingly, the material is
entirely suitable for rainy climates, and so long as a cob house is
reasonably cared for, the structure will not deteriorate; many cob
cottages in Devon (one of the wetter counties in England) have been
inhabited for hundreds of years. Cob has many similarities to the adobe
associated with Mexico and the southwestern United States, but whereas
adobe is formed into bricks which are then stacked into a wall system,
cob is sculpted from the foundation up.
Cob has recently been rediscovered as a low-cost and artistic building
technique, and cob houses are now being built again.
