Thursday, February 22, 2007

Building with Cob 4: Additional Resources

Apparently I have been getting some notice from the cob building community, as I have been added to the I Love Cob blog links. This is great, as the blog is an excellent source for cob builders in the Southwest. The blog also provides some great references to anyone that would like to build their own cob home, and do so to code.

The great news is the reference to From the Ground Up, which is a documentary that was run in Home Power Magazine regarding the building of a cob home in North Carolina to code, and how they did it. There are a few things that I learned from their article:

1. Roofing needs to be keyed
Keying a roof means that you add additional pieces of wood to your roofing beams, to give the cob something to "grab". This is necessary both for heavy loads (i.e., snow), and updrafts from heavy winds. For those that are familiar with the Utah climate, you will know that we are often blessed with summer micro-bursts of 60+ mph winds.

2. Foundation needs to raise the cob wall at least 10 inches from the ground
I knew that the cob wall needed to be off the ground to keep moisture levels in the wall low, but the exact number was not made clear. Now, I know, and knowing is half the battle. ^_^

3. Non-load bearing walls can be thinner
While this doesn't matter that much for my future projects, for my current project for the back porch, it's great to know! I was worried that I would need to build a 16" thick wall for each side, even though it would not be necessary to hold the roof in place. Now I can make the wall 9" thick, and save some interior space.

4. Insulation and R-factor
I'm not very familiar with construction rules, and insulation is something that I generally take for granted. What I didn't know is that cob as an insulation R factor of R-0.25 per inch thickness. This means that I can either use a vermiculite or perlite mixture with the cob, which gives a R-2 to R-4 per inch thickness, which would make a 9" wall well within the R-factor ratio that most building inspectors would like it to be. Better to know that now than after building! ^_^

5. Code regulations exist for cob in various States
Yes! There are some states that have alternative building material codes that already exist. In fact, Arizona has one for cob under "Monolithic Adobe". Other building codes like the Uniform Building Code and the International Building Code acknowledge non-fired clay masonry, but not a monolithic structure. So, if you can talk your local building inspector to accept the codes from Arizona, then you are in business! I don't see that happening in my situation, but my goal is to get cob accepted within West Valley, though I may need to work at it from the State level. We will see...

So, I just thought I would throw up that update to let you know what is happening. I have another post that I am preparing regarding the farm idea, so stay tuned! ^_^

1 comment:

Mellifera said...


Thank you so much for doing this! We are also looking to farm in the future ourselves, want to build in cob, and are pretty anxious about whether it could ever be permitted. (Living in an unpermitted structure is one thing, but conducting a business out of it-- nuh-uh.) The info and links you have here are very encouraging. So there you go, you can count us as the first people to benefit from your illogical determination to do everything legally. ; )

FWIW (and you may have already heard of these), masonry stoves [or mass stoves, or Finnish/Russian stoves, etc] sound like a brilliant way to do heating in masonry buildings. If you're not familiar with the idea go ahead and google "masonry stove," they're fabulous. Can you tell we want one?

PS: On a final note, we recently finished school at BYU. It's so exciting to see green architecture going up in West Valley City, of all places. ; )