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Kiko Denzer on Art

[Cob] Could "light clay" be load bearing if baled, and would it mold?

howard at howard at
Tue Dec 30 14:39:39 CST 2008

>I would build with straw bales, but the mold issues concern me.  


Any mold issues with straw bale construction can be avoided by making sure bales never set against a wet membrane or otherwise get and remain wet.  (Not good for any building material.)  Actually light clay straw has more mold associated with it but as it dries that mold disappears and is not an issue.  I had a client call me up once very concerned about the grass and mold growing from the light clay-straw and cob we had installed in his house. I went out and swept up some of the white mold on my finger and stuck up my nose to show him it wasn't harmful and explained it would be gone soon so not to worry.  Molds are part of our reality, we just need to have right relationship with them. 

You can get a good idea of the structural capacity of your material by building a small test panel and loading it up with a point load.  Perhaps build a half wall panel 4 feet high and long and use it to support one end of a timber say 12' long and see how many people, or how much weight, you can get on it before the wall panel begins to fail.

Cob should have a lot of straw in it, about as much as any particular mix can take, I would say.

I hope this is helps,

Howard Switzer, Architect
668 Hurricane Creek Road
Linden, TN 37096