Cob (building)
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Cob is a building material consisting of clay, sand, straw, water, and earth. Cob is fireproof, resistant to seismic activity, and inexpensive. It can be used to create artistic, sculptural forms and has been revived in recent years by the natural building and sustainability movements.
[edit] History and usageCob-building is a traditional technique that has been used for thousands of years and in all kinds of climates. In the UK it is most strongly associated with counties of Devon and Cornwall in the West Country, and the Vale of Glamorgan and Gower Peninsula in Wales, where many cob cottages have survived and are still inhabited. Many old cob buildings can be found in Africa, the Middle East, Wales, Devon, Ireland, Cornwall and some parts of the eastern United States. 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. Traditionally, English cob is made from the clay-based subsoil, mixed with straw and water, either by people shovelling or stamping the mass, or using oxen to trample it. It’s then ladled onto a stone foundation in courses and trodden into place by workers. After drying for up to two weeks, the walls would be trimmed and the next course added, with openings for doors or walls either built in, or lintels added and the material carved away after construction was completed. Where sand is not readily available paper pulp may be added to the clay to minimize cracking when the cob dries. [edit] Modern cob buildingsWhen Kevin McCabe built a two-storey, four bedroom cob house in England in 1994, it was reputedly the first cob residence built in the country in 70 years. His methods remained very traditional; the only innovations he added were using a tractor to mix the cob itself, and adding sand or shillet (a gravel of crushed shale) to reduce the shrinkage. In 2006, a modern, four-bedroom cob house in Worcestershire, UK,designed by Associated Architects sold for £745 000. Cobtun House was built in 2001 and won the Royal Institute of British Architect's Sustainable Building of the Year award in 2005. The total construction cost was £300 000, but the metre-thick cob outer wall cost only £20 000.[1] In the Pacific Northwest of North America there has been a resurgence of cob building both as an alternative building practice and one desired for its form, function and cost effectiveness. There are more than ten cob houses in the Southern Gulf Islands of British Columbia built by Pat Hennebery and the Cobworks workshops. Go here for examples of modern cobbing. [edit] See also
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