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10 years of cob

It has been about 10 years since I took my first 1-week cob workshop. I sank my bare feet into the mud to mix the sand straw and clay together, wondering how this could possibly lead to the building of a house.

I have now designed and built more than 30 structures and taught workshops all over the USA and the world. I want to share some of my reflections on cob building, the materials, the method, the community and it’s place in the world.

The beauty of cob

Cob buildings are virtually irresistible! The beauty of cob buildings far surpasses that of any other building style. I have yet to find a cob building that was not magical, even though almost all cob buildings were designed and built by novices. The combination of thick, earthen walls with the freedom to sculpt your house as you build it, leads to a quality of space that is impossible to describe or draw. In my experience it is the building style that people worldwide fall in love with the easiest.

Thermal performance of cob Due to its mass, it out-performs every other building style (including straw bale) in all but the coldest (northern) climates. Given a good passive solar site, the cob not only stores the heat well, it has the quality of providing comfort at a lower temperature then other houses. As I am writing this the temperature in my house (Straw bale cob hybrid) is about 60 degrees. People have found that surrounded by massive walls that are radiating 60 degrees is more comfortable than having warm air blown through the house (convection heat) at 70 degrees. That makes a lot of sense as air movement adds a “windshield factor”, cooling you off by evaporating the moisture on your skin (mostly your head).

The strength of cob Although I don’t have any engineering data available, I have had to take some cob walls apart and I was always awestruck by how hard that was. We’d use grinders, saws-alls, jackhammers, drills, sledgehammers and more, but still have not found an easy way to demolish a cob wall (short of putting a hose on it for a couple of days). In part the strength of cob depends on the properties of the ingredients that are being used. Having said that I have discovered that in relation to strength, cob is very forgiving. Interestingly enough, we have found that in particular adding a lot of good long straw to the mix adds incredible amounts of strength to the material.

The time it takes to build with cob We have found that building with cob is about as fast as any other building style, conventional or alternative. During the workshops people are often questioning the speed of cob, as we build everything by hand as mix everything by foot. However, add a tractor and some power tools, and cob will go as fast as any other building technique, which also uses a large amount of power tools. Think about it this way: In conventional construction builders buy materials that are prepared in a form that has led to huge time-savings: The tree does not need to be peeled and sawed anymore, but comes in the shape of a 2×6. One could pay someone to harvest clay, sand and straw and deliver it in the form of cob to the job site. In either case the job will go a lot faster, but also at a cost: People are more prone to get hurt, the building site becomes loud and unpleasant, the building tends to become less personal, unique and infused with the human spirit. Most of all, the attitude at the jobsite tends to slide from lovingly enjoying the building process to grinding your way through the day in order to get the building done. You choose!

The cost of cob buildings The cost of any building, including cob, depends on how much money you spend on materials and labor. Doing everything g yourself may save you some money, but you have to take into account that as you are building you are not working somewhere else to make money. Work parties and workshops can help a lot; so do finding second hand doors and windows for free. In that sense, the notion that cob is so inexpensive has been exaggerated. It all depends on how creative you are in finding free things and getting people to help you. I have built several small stick frame buildings for next to nothing. On the other hand there are examples of cob houses costing $500,000 and up.

Cob and building codes By and large, people still seem to have a difficult time getting cob approved by the building officials. Here are a few thoughts:

  1. I think a lot of people don’t even try to approach the building department because they seem so intimidating. Get to know the code and find out who is the best person on the building department to talk to about cob; you may be surprised.

  2. In many areas in the United States there is no building code enforcement. Cob will do just fine there.

  3. Some counties have what is called “owner builder code”. That means that, as long as your electrical and plumbing are up to code, you can pretty much do whatever you want after that. In California, Humboldt, Mendocino and Nevada counties know such a code.

  4. You only run into difficulty with the code if you were to choose to build a house just made out of cob. If you support the roof by a few wooden or metal studs, you can pretty much do whatever you want to after that. You can usually also build internal cob walls, do earthen plasters and floors and add garden walls to the outside of your building.

  5. Even with no cob inside your house, building ovens, fireplaces and walls in your backyard will be a great addition to your place.

Cob and the workshops For many people the workshops are life changing. The following come from an e-mail I just received recently:

“…I am going on, but I am excited and happy. I know that I would not be making the life changes I am involved in if I hadn’t taken that first workshop in Julian and then participated in the Pine Ridge adventure. Thank you for inspiring marvelous changes in my life and in my daughter Gabrielle’s. Now my younger daughter and her boyfriend want to participate in a workshop with me. We will do it.” I receive these letters on a regular basis. Although people come to the workshop because they want to learn how to build a house, they often walk away with something more valuable: A whole new outlook on life! Building with earth is a transformative experience that in combination with quality instruction, good food, a beautiful place and a fun group of people can lead to new insights, capabilities and hopes for everyone.

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