Cob building is the art of building homes using earth materials. Earth has been used for thousands of years as a building material, and is probably still the most common building material on Earth. The word ‘cob’ comes from an old English word that means ‘a rounded lump or mass.’ We get our word ‘gob’ from the same root word. Cob is basically a mixture of straw, sand and clay. These natural building materials are often available right on the building site, so transportation costs for materials are greatly reduced or eliminated altogether. Once the walls are built (by stacking the cob 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. An artistically designed cob home fits in with its surroundings. These structures feel more at home and in harmony with natural landscapes. In addition to making beautiful homes, 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. Many cob homes I’ve visited have been built for less than $5,000, and a few have been constructed for less than $500! Not only that, but it’s so easy a child could do it. Ever make mud pies when you were a child? Then you’ve already got most of the basic skills to build with cob!
Cob is at home in most environments. 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. A friend of mine once built a cob pottery studio in Gulf Breeze, Florida. It survived two hurricanes, even when the surrounding buildings were demolished. Many cob structures in earthquake zones have demonstrated remarkable durability as well. No building system is earthquake-proof under every seismic condition, but a cob mansion in Nelson, New Zealand has survived two major earthquakes that destroyed the town around it. In South Yemen, in a fault zone, there are medieval cob houses 13 stories high. A cob building is one monolithic unit reinforced by straw, so it has no weak straight-line mortar joints, making it stronger than brick or block. Cob is also non-toxic and recyclable. 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 directly from the building site, it doesn’t use fossil fuels transporting materials to the site. When properly constructed, it is highly resistant to rain and humidity even in environments such as the Pacific Northwest and the British Isles. In fact, of the hotbeds of cob building right now in the United States is Oregon!
Due to the fact that walls in a cob home are one or two feet thick, they offer excellent thermal properties. When built with passive solar design in mind, these homes often don’t require extensive heating or cooling in temperate climates. The earthen walls capture heat from the sunlight in the daytime and radiate it at night. Such homes rarely need cooling in the summertime, and can be heated with a small wood stove in the wintertime.
The tradeoff with a cob home is that it is a labor-intensive process. The savings come in part from getting the materials for free, straight out of the ground. Building it yourself means additional savings. You keep the money that would have gone to pay a contractor. If you’re not a hands-on, do-it-yourself type of person, cob is probably not for you; but if you don’t mind getting your hands (and feet) dirty, then cobbing can be a very relaxing and meditative experience. Most of the cob structures I’ve seen were built by groups of people in ‘cobbing bees,’ where friends and neighbors get together for a weekend or two to share the experience. Since no power tools are involved, people often spontaneously break into song or conversation while cobbing together. It’s a great opportunity to socialize while doing something positive for yourself and the environment! In fact, people who have experienced cob building firsthand often talk about it in terms usually reserved for those who have undergone a religious experience. Cobbing brings people together at an instinctual community level.
Due to the fact that cob is labor-intensive; cob homes are usually smaller than the average stick-built home. This loss of space isn’t really that noticeable in a well-designed cob home because you can shape alcoves and shelving right into the walls to take advantage of vertical space. The organic shapes that are possible with cob also make it possible to use space more efficiently. By building smaller, more space-efficient and natural buildings, not only can you save on building costs, but you also save on the energy required to heat, cool and light the extra space. Cob homes can be designed to make living more comfortable in less space, so they’re perfect for the tiny homes revolution.
Cob homes may take a little longer to build than a traditional home, but there are several factors that can come into play, including the weather, the size of your cobbing crew, and the size of your home. A crew of six to twelve people can build up to a foot of height per day in a cob home of about 800 square feet or less. One advantage to cob building is that other than applying plaster to the finished wall, there is no finish work required. Plumbing and electrical fixtures are laid in place inside the wall as it is built, and there is no framing to be done. There is no need for insulation, sheet rock, taping, and finish framing. Once the final plaster coat is applied, the walls are done.
I have seen a small cob cottage (about 300 square feet) built in one weekend by a dozen dedicated workers. But racing to finish the home is missing the point. If you’re in a hurry to build, cobbing is probably not for you. Half the fun in building with cob is in taking time to feel the materials take shape under your hands. It’s a very tactile experience, similar to sculpting with clay. If you have a ready stable of volunteers, you’ll find that your group will eventually settle into a rhythm that is almost like a dance. Since there are no power tools, you can enjoy the sounds of nature while you work. Cobbing is an activity that naturally lends itself to parties, since it doesn’t require a lot of skill, and who doesn’t like playing in the mud! It’s a chance to indulge your inner child; and if you have children of your own, they’ll love it! If you don’t mind putting a little sweat-equity into building your own home, it makes a lot of sense to return to nature’s most abundant, inexpensive and healthy building material!