In Old English, cob
was a root word that meant lump
or rounded mass
. Cob houses are made of clay-like lumps of soil, sand, and straw. Unlike adobe and straw bale construction, cob does not use bricks or blocks. Instead, wall surfaces can be sculpted into smooth, sinuous forms. A cob home may have sloping walls, arches and lots of wall niches.
Cob homes are one of the most durable types of earth architecture. Because the mud mixture is porous, cob can withstand long periods of rain without weakening. A plaster made of lime and sand may be used to windproof the exterior walls from wind damage.
Cob houses are suitable for the desert or for very cold climates.