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Foundation question

 
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Hey all! I have a question that might be stupid but here we go anyway.

I'm in the planning stages of a home. I'd like to do aircrete wall panels with earthen floors, but I'm having a hard time figuring out the issue of a foundation. Ideally I'd like to do a rubble trench foundation. I really don't like the idea of a concrete slab- the idea of walking on concrete for the rest of my life seems unpleasant. We're building in northern MN, and the typical foundations here are slab on grade or basements.
My idea was to do a rubble trench foundation with an insulating frost apron, but instead of a concrete slab use some kind of natural material, a layer of insulation, then an earthen floor with radiant heat. My husband is concerned that without the concrete slab the house would be more susceptible to shifting from freeze/thaw. I haven't been able to find anything online about a slab-free foundation that isn't a crawlspace.
Has anyone here had experience with this? Or maybe know a guy who knows a guy who's done something similar? I'm not even sure if it's a viable option, but any info or ideas would be greatly appreciated.
Thanks!
 
Rocket Scientist
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Location: Upstate NY, zone 5
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Frost heave requires frost to get underneath the structure. If you have a good insulating apron as in "frost-protected shallow foundation" style, this should not be an issue.  

This pdf assumes a concrete slab, but is applicable to anything:
Filename: Revised-Builder-s-Guide-to-Frost-Protected-Shallow-Foundations-Revised-Builders-Guide-to-Frost-Protected-Shallow-Foundations.pdf
Description: Frost-protected shallow foundations
File size: 11 megabytes
 
pollinator
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Hi Betsy, my house is built with a rubble trench foundation with layer of insulation on the outside of the foundation to prevent heave. I believe in MN you would need the apron to extend out from the foundation 2 feet, but I would double check. With a shallow trench foundation you are relying, I believe, and someone please correct me if I am wrong, relies on trapping the heat from the stable earth temp and the heat produced from the house. Even with some insulation you are going to have heat loss to the ground which is actually positive for those cold winter days when you are preventing frost from ruining your foundation. The rubble trench is also superior in that it wicks moisture away from under the house. No water, no frost, no heave.

No concrete slab is necessary for your construction of an earthen floor. Just level, put down 4-6" of gravel, use a moisture barrier, put down rigid foam insulation, do a base earthen layer (quarries have road base that works well), then do a finish layer of earthen floor that gets oiled once dry.

 
master gardener
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Hi Betsy,

Welcome to Permies
 
pollinator
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try this for aircrete information.
 
Betsy Nelson
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Thanks everyone for the replies!
I appreciate all the info, very excited to move forward with these earthen floors. Also, thank you for the info on aircrete, the more research I do I believe this is about the perfect building material for our cold climate. I think combining the insulation of aircrete with the thermal mass of earthen floors and a masonry heater should work together to keep our upcoming home nice and toasty.
If anyone has more ideas, keep em coming! What a wonderful community, looking forward to kicking around more ideas with all you great people!
 
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