My buddy and I are very new to cob, but are eager to try a small project in our 16 ft yurt. The stove currently sits on and in front of cement board, which I would like to cover in a few inches of cob and clay plaster. Both for aesthetic purposes AND thermal mass. Assuming we have plenty of insulation around the yurt itself, can anyone think of any reason this would not be as effective in maintaining warmth as I think? Also, any reason that I happen to be overlooking why I shouldn’t attach cob to the cement board? The yurt is able to be relocated, but will remain permanent for at least the next 5 years.
Hi Sara, Welcome to Permies. A photo would be great to give us an idea of what you are planning, but your plan sounds good. The mass of the cob would definitely give you a slower release of heat which is always good so the thicker the better. If the cob is too thin, it wont hold the heat very long and will shed it off much quicker. I would recommend 4" or more to really hold some heat, but you may not have enough space for that much.
The cob will attach fine to the cement board if it is given something to grip. Use cement screws all over the face of it for the cob to grab onto. If you can't get screws, you can make a wheat paste, mix it with course sand and paint it on the surface before applying cob, this should help it adhere. It would also help to start the cob several inches wider at the floor level and taper it in slightly as you work.
If you want something easier to deconstruct, but looks nice. If you can find some old red brick I would suggest stacking that behind the stove instead of cob, unless of course you are just too darn excited about cob, which I totally get.
Thank you. I was seeking validation and I think your post was exactly what I needed. I hadn’t thought about something for the cob to adhere to and bricks might be a good add for this current winter. Both of those are useful for getting to the next step of the planning stage! I appreciate it!
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