I have been looking for a while and have only found two options recommended for a foundation for cob. First dry stack stone second dry stack urbanite.
What other options have people found?
Would a poured concrete foundation work?
How about a block foundation?
Is there anything extra that needs to be done if not doing a dry stack foundation?
I'm hoping to build a 400-500 sqft cob house this year the North and West walls will be straw bail. I have not finished reading The Hand-Sculpted House but I'm working on it.
The reason that I want to use other materials is because they will need to be trucked in and I do not have a truck currently so as few deliveries as possible would be great. Extra block would be used to build a cistern or two that would be used to hold rain water and as part of the heating/cooling system low temp hydronic.
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Hi Sean, a concrete foundation can definitely be used for cob/strawbale. Most of us green builders try to stay away from concrete because it is so freakin' expensive and has one of the highest embodied energy contents of any building material. With that said, it's stong, lasts for generations, and is convenient....which is why it is so popular. When we do use it, we try to use as little as possible. At Sage Mountain Center, we've come up with a "floating grade beam" design that is a combination of a floating slab and a footer. The beam is formed with wood and filled from a concrete truck. It rests on top of a rubble/rock filled trench (three feet deep at our elevation of 6,400') It's basically a continous floating beam. Ours is 12" high X 16" wide, with 4 sticks of rebar suspended in the middle. There are no seams or joints like in cinder block, stacked stone, or Urbanite. This greatly minimizes cracking in the walls and gives a nice smooth surface for sealing and insulating the perimeter of the foundation if desired, if so desired. Chris
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