Cob - What is It?

Earth is probably still the world's most common building material. Cob building is the art of building homes using earth materials. Usually when I tell someone about cob for the first time, they think 'corn cobs.' That's not what it's really about. The word 'cob' comes from an old English word that means 'a rounded lump or mass.' We get our modern word 'gob' from the same root word. Cob is basically a mixture of straw, sand and clay. Once the walls are built (by stacking the cob balls or lumps to build walls) they are covered with plaster to seal them. There are no forms, brick shapes or frames. Since cob is basically the same consistency as modeling clay, it lends itself to organic shapes that are more curved and natural. Cob can also be used to build sculpture, garden walls and outdoor ovens. 

Cob is literally 'dirt cheap' since it is made from materials readily found in nature. It can also be sculpted to provide beautiful artistic touches to your home, as these pictures illustrate. Not only that, but it's so easy a child could do it. Ever make mud pies when you were a kid? Then you've already got most of the basic skills to build with cob! In fact, as a child growing up on the farm back in the late 1960s and early 1970s, I built play forts with cob before I even knew what it was called. Cob is almost instinctive.

Cob has been around for thousands of years. Some of the earliest structures on Earth, in the Mesopotamian region, were made of a type of cob. There are cob homes in Western Europe that have been continuously occupied for centuries. With a little regular maintenance, a cob home is extremely durable.

Cob is also non-toxic. It is made from natural materials that contain no toxins. Cob doesn't require any products that don't come directly from the Earth. This ancient way of building also doesn't contribute to deforestation, mining or pollution. Since it is a natural form of building, it does not rely on manufactured materials. Since it is made using materials on the building site, it doesn't use fossil fuels transporting materials to the site.

One drawback of working with cob is that many building inspectors are unfamiliar with the material. Cob is not covered by most building codes; however, adobe is covered in many. If you can convince your local building inspector that cob is a modified form of adobe, you may have better luck in getting your project approved. Another drawback is with insurance companies. Most won't insure cob because they have no experience with the material. There's some tradeoff in this department. You might not be able to get the building insured, but since cob is so durable and cheap, in the unlikely event that a disaster occurs and damages your building, it can be rebuilt for about the same amount of money that you would have spent on insurance premiums. If this is really a concern for you, consider the fact that cob itself is fireproof and extremely durable. For a story of about how her first cob studio survived a hurricane, visit Christina Ott's Barefoot Builder website.

If you are having problems with the local building inspector, this can usually be worked around by finding an architect or an engineer who has experience working with cob. If you can get an architect to sign off on your project, most building inspectors will work with you. I'm starting a list of architects and engineers who work with natural materials. If you are such an architect, or you can recommend one, please email me and I'll add their name to the list.