Cob

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Cob is a traditional British building technique that uses a mixture of clay, sand and other binders to create walls that can reach several stories. The material has stood the test of time - there are still many buildings in Devon that have been standing for several hundreds of years made from cob.

The technique has been revived recently, arguably by Ianto Evans, Linda Smiley and Michael Smith of The Cob Cottage Company in Oregon. They changed the mixture proportions and ingredients slightly to reflect more modern thinking. This is the “What is Cob” introduction given by the Cob Cottage Company:

Earth is probably still the world’s commonest building material. The word cob comes from an old English root meaning a lump or rounded mass. Cob building uses hands and feet to form lumps of earth mixed with sand and straw, a sensory and aesthetic experience similar to sculpting with clay. Cob is easy to learn and inexpensive to build. Because there are no forms, ramming, cement or rectilinear bricks, cob lends itself to organic shapes: curved walls, arches and niches. Earth homes are cool in summer, warm in winter. Cob’s resistance to rain and cold makes it ideally suited to cold climates like the Pacific Northwest, and to desert conditions.

Cob has been used for millennia even in the harsh climates of coastal Britain, at the latitude of the Aleutians. Thousands of comfortable and picturesque cob homes in England have been continuously occupied for many centuries and now command very high market values. With recent rises in the price of lumber and increasing interest in natural and environmentally safe building practices, cob is enjoying a renaissance. This ancient technology doesn’t contribute to deforestation, pollution or mining nor depend on manufactured materials or power tools. Earth is non-toxic and completely recyclable. In this age of environmental degradation, dwindling natural resources, and chemical toxins hidden in our homes, doesn’t it make sense to return to nature’s most abundant, cheap and healthy building material?

Here’s a nice example of a well planned, well made, cob house:

http://www.cobworks.com/maynegallery.htm

In line with ‘natural building’ philosophies, the house is positioned for maximum solar gain - using the low sun in winter to provide additional warmth, whilst the large roof overhang not only protects the walls from rain, but shields the house from direct sun (i.e. heat) in the summer. The thermal mass that cob provides enables the walls to soak up warmth during the day in a massive heat sink and release slowly at night - the net result is a house where the temperature should remain more even and be more comfortable than a ‘conventional’ dwelling.