"Cob is a structural composite of earth, water, straw, clay, and sand, hand-sculpted into buildings while still plaible. There are no forms as in rammed earth, no bricks as in adobe, no additives or chemicals, and no need for machinery."—Ianto Evans, The Hand-Sculpted House, 2002, p. xv.
cob "A mixture of straw, gravel, and unburnt clay; used esp. for walls."—Dictionary of Architecture and Construction, Cyril M. Harris, ed., McGraw- Hill, 1975, p. 111.
cob wall "A wall formed of unburnt clay mixed with chopped straw, gravel, and occasionally with layers of long straw, in which the straw acts as a bond>"—Dictionary of Architecture and Construction, Cyril M. Harris, ed., McGraw- Hill, 1975, p. 111.
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.
The Hand-Sculpted House: A Practical and Philosophical Guide to Building a Cob Cottage by Ianto Evans, Linda Smiley, and Michael G. Smith, Chelsea Green Publishing Company, 2002
The Cob Builders Handbook: You Can Hand-Sculpt Your Own Home by Becky Bee, Groundworks, 1998
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