Cob is an earthen building material that is made of clay, sand, straw, and water. It has been used for thousands of years to construct homes and buildings. It has been used worldwide, but has only recently started to attract interest from Western countries. Cob has its origins in millennia of traditional building, in some of the oldest permanent human dwellings. Humans have made shelters this way for so long that we may carry a genetic memory of how to do it.
The word ‘cob’ comes from an old English word meaning ‘lump’ or ‘loaf’. The wet cob mixture is used to build thick earth walls; the building technique is very similar to sculpting with modelling clay. Because cob building requires no forms, we can build our walls into any shape we choose. Curves, niches, arched windows and built-in furniture are common features in cob buildings.
Cob building requires no cement, no expensive tools or materials and is a ‘people friendly’ way of building. Once the material is dry, cob is incredibly strong. The drying-out, setting process of clay products can be reversed if necessary, so even when the building material is hard and dry, you can usually alter it by wetting down whatever you want to change. This is different from lime and concrete products, which set and become hard through an irreversible chemical process.
Often we can find the bulk of the materials on or near the building site. In natural building, we make an effort to build with materials that are found locally. Unless they are recycled materials, we also prefer to harvest these materials ourselves, with the least amount of industrialization, so that we can be gentle on the earth.
One of the most commonly asked questions about cob is “What happens when it rains?” The cob tradition originates in England and Wales — which are not dry places by any standard. These areas have whole villages of cob buildings, many of them hundreds of years old. The secret is the same as that of any building style: A good roof and a good foundation are the keys to survival in wet climates. Cob works well in all climates. If it gets too cold, it is easy to add extra insulation on the outside of a cob building. Cob houses benefit greatly from good passive solar design.
For all these reasons and more, cob is an almost ideal building material — offering new advantages and opportunities to the developed world. Building with earth and other natural materials is becoming a solution to our world’s energy and consumption problems. Cob is dirt cheap and ecologically friendly. It is easy to learn, inexpensive, beautiful, healthy, comfortable and the materials can be found almost anywhere
Besides the above-mentioned advantages over conventional building methods, cob can offer people a way out of the crazy real-estate market, an unhealthy lifestyle and a job with no joy. Many people who never considered themselves builders have created a cob house for themselves. Cob is useful for much more than houses, too. You can make cob ovens, fire places, cob furniture and cob floors.
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