Cob Building Tutorial

Chapter 1: What is Cob?

Video: An Evening at the Moon Unit:

  Modern building methods are very taxing on the environment. Cement production is one of the most energy intensive of all industrial manufacturing processes.  Cement production now accounts for over 8% of total carbon dioxide emissions from all human activities. Cement kilns in the United States are the third largest source of dioxin contamination. Part of this is due to the fact that kiln operators are allowed to burn toxic wastes as fuel. Concrete trucks require about 500 gallons a day of highly alkaline wash water to operate. This type of water is toxic to fish and other aquatic life.

Steel, another predominant building material, is made from iron ore and other non-renewable resources. Steel production is energy intensive due to the amount of heat required. The fuels used to fire steel forges are also a major source of carbon dioxide and other forms of air pollution air pollution.

Vinyl siding and other plastics used in the construction industry are made from non-renewable petroleum by-products. Plastic manufacturing requires toxic chemicals and produces more toxic waste. Plastics don't breathe like natural building materials. Many plastics emit toxic fumes. Some plastics can take up to 50,000 years to deteriorate!

Commercially harvested lumber products are usually treated with preservatives that are highly toxic. For example, arsenic is a component in many pressure-treated lumber products. Commercial forests harvested for lumber often use hazardous pesticides and preservatives. Irresponsible deforestation causes soil erosion, contamination of waterways from silt and pesticide runoff, and loss of biodiversity in the forest ecosphere. Composite wood products such as plywood and other particulate boards are often held together with toxic compounds which in addition to contributing to the degradation of the environment, are suspected to cause allergies and other health problems.

Commercially manufactured building materials cause problems for health and the environment at all stages of their life cycle, from production and manufacturing, to use in building, to disposal when buildings are razed. Additionally, long-distance transportation of building materials contributes heavily to transportation costs, not to mention the additional pollution caused by the large diesel-burning engines required to transport them.

Clearly our current methods of building homes are extremely taxing on the environment! But there is a better way.

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. In my home state of South Carolina, 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. According to the U.S. Census Bureau, housing square footage is four times larger today than it was 40 years ago, and couples living alone occupy nearly half of these homes!  Think about how much unused space you have in your home now and you’ll see the advantages of a smaller home. 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.

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.

About the pictures in this tutorial: Not all of the cob structures in the pictures shown here were built by the Culture Artist Cobbers. Many are from cobbers at various sites around the world. I have attempted to get permission for all the photos used on this site, and to properly credit them wherever possible. When the cobbers in question have a website, I have tried to link the picture back to their site, or list them in the Cob Builders' Directory, or both. I have made every effort to gain permission for all the pictures shown. If I inadvertently used one without permission, please contact me at chuck@cultureartist.org and I will either credit the source or remove it. Thanks!

Chapter 1	Chapter 8	Chapter 15
Chapter 2	Chapter 9	Chapter 16
Chapter 3	Chapter 10	Chapter 17
Chapter 4	Chapter 11	Appendix A
Chapter 5	Chapter 12	Appendix B
Chapter 6	Chapter 13	Appendix C
Chapter 7	Chapter 14	Appendix D