What is Cob?

Cob is a building material that is usually made of a mixture of sand, straw and clay. The materials are mixed wet, by foot or with a mechanized method (tractor or mortar mixer).

One can then use this mixture to build strong, thick earthen walls, using the cob as if it were "modeling clay". Often we make "cobs", blobs of material about the size of a loaf of bread, with which we then sculpt our house, giving us the ability to easily make curved walls, arched windows, niches, built-in furniture, etc.

Cob involves no forms, no ramming, no cement, no expensive tools or materials and a "people friendly" way of building. Often we can find the bulk of the materials on site.

Once the material is dry, cob is incredibly strong (trust me here; I have had to take cob walls apart!). Although there is no conclusive research done on cob in earth quakes, there is all the indication that they would do great: Many cob buildings have survived major earthquakes. In Yemen, many 10 story cob buildings have been there for over 500 years.

How about moisture? England and Wales, no dry countries by any standard, know 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 key to survival in wet climates.

Cob works well in all but the coldest 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. It is easy to learn, inexpensive, beautiful, healthy, comfortable and the materials can be found almost world-wide. It is no wonder that about half the world population is living in a variation of a cob house.

In the United States, cob is experiencing a growing popularity. Besides the above mentioned advantages over conventional building methods, cob often offers people an 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. There are now hundreds of cob buildings in the USA, with a concentration in Oregon and California.

Once you know how to build with cob, it also enables you to do more than build walls. We teach how to build ovens, fire places, earthen plasters and cob floors. Garden walls are among the most popular application due to their "beautification power". Cob can easily be integrated with a conventional house and used to practice "natural renovation".