[Cob] Foundations for stoves and interior cob walls

[Amanda Peck]

We had an earthquake in the county recently, but they've always been small 
and rare.  This has been true every place I've lived.  So I know next to 
nothing about building in seismic areas (although there could be a "big one" 
just a little over a hundred miles away).  And I'm not an engineer.

But if I'd thought about it at all, I'd have thought that for frost heave 
and the like, an 8-foot deep perimeter foundation (are you insulating and 
waterproofing or draining the outside, by the way?--and how much extra would 
a basement be?)  would keep the earth under the building the equivalent of 
Tennessee near the Alabama-Mississippi line.  So an 18" deep 
foundation/footing for an interior hearth would work just fine.  Footing 
several inches thick, come up out of the ground with concrete block or 
concrete or mortared urbanite (with or without lines of rebar or barbed wire 
embedded in the mortar) and a rubble fill, probably something like that 
heavy roll fencing they embed in concrete to keep it from making a sinkhole.

I may not do that much, although for a heavy building--e.g. cob--I expect 
that I will have to do a real, down-to-frost-line footing for the building 
foundation, and that will require a lot of earth moving in general.  So if I 
want the stove built on undisturbed earth (good idea) I may have to do a 
standard foundation for it (and around here, that's about what I just 
described).

.............
Anna wrote:
A question about stove and interior cob wall foundations. We are doing the 
formwork for our cob/strawbale house concrete bond beam at present (thanks 
to living in an earthquake zone). The plans specify the same 2-3' wide, 8' 
deep footing for an interior cob wall and masonry/woodstove stove as for the 
main outside walls. This is a lot more cement and feels like overkill to us. 
However, if we do a stone or urbanite foundation starting higher up, above 
the waterproofing barrier, it will be on a lot of infill earth. Well-tamped, 
but it might settle over the years. Any thoughts / comments / experience?