Cob Building

by Chuck Hall

Throughout most of the history of humankind on this planet, homes have been made of some type of earth. In the Mesopotamian region, bricks made of clay and straw were used for construction for thousands of years. Variations on this type of adobe can be seen all over the world. In fact, most homes today are still made of some sort of earth.

A method of building with earth, called cob, is similar to adobe construction. Cob, like adobe, is a mixture of straw, sand and clay. The difference in cob building is that with cob you don’t form the mixture into bricks. It is built layer upon layer ‘freestyle.’ Once the walls are built, they are covered with plaster to seal them from the elements. Cob is durable, comfortable and non-toxic. It can be modified to suit almost any climate. There are cob homes still standing in England that were built in the 16^th century!

Cob is a versatile and aesthetic material in that it can also be used to build sculpture, garden walls and outdoor ovens. Since its major component is clay, it can be sculpted into any shape that will bear the weight of the materials. Cob is literally 'dirt cheap' since it is made from materials readily found in nature. Not only that, but it's so easy a child could do it. If you ever made mud pies when you were young, then you've already got most of the basic skills to build with cob!

One drawback of working with cob is that many building inspectors are unfamiliar with the material. This can usually be worked around by finding an architect or an engineer who has experience working with cob. Cob is not covered by many building codes, but adobe often is. If you can convince your local building inspector that cob is a modification of adobe you might have better luck than you would otherwise. Get an architect or construction engineer to work with you, and most building inspectors will issue a permit. The amount of difficulty you may have obtaining a permit will depend on the local building inspector’s experience with alternative building materials. It can sometimes be an uphill battle, but as more inspectors become educated in this great sustainable alternative, the process will become easier. The beautiful results that can be obtained are well worth the extra effort. If you’ve never seen cob construction, http://www.cobprojects.info/ is a great place to start.