Frost-Protected Shallow Foundation for Unheated Building
Question: Does anybody have experience using a frost-protected shallow foundation for an unheated (or semi-heated) structure? How’d it go? Apart from a builder’s guide from 2004, there’s a dearth of information online for this setup, so I’d love to hear if anybody has had success with it.
Location: Near Halifax, Nova Scotia. Winter climate is comparable to Portland, Maine (6A) so it’s safe to use that as a proxy.
Context: The building is 32’X22′ with a garage on the ground floor and an ADU above. With the exception of a small utility room, the garage portion will be unheated, with exterior walls insulated to code. The engineer and foam rep are confident in a continuous sub-slab layer of R-10 EPS, with 4′ of R-10 foam extending from the edge of the foundation. There will also be R-10 foam running vertically up the slab edge.
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