Wisconsin (AFI 3000) new slab sitting unheated all winter
I am designing a frost protected shallow foundation (FPSF) and have a few items I am contemplating. I am starting a 1300 square foot cabin with a 1 car attached garage.
The cost difference between a frost wall (10k) and a FPSF (5k) is about double. I am working on this with just a few people where the cost savings, materials, excavating and equipment seem to favor a FPSF. I would love to get the slab completed in August and September, I would have to leave the slab unheated for the winter. I could have part of the framing completed before the 70 inches of snow fall, but would certainly have some of the slab without framing. I have labor and time ready to go for a month in August/September; money is the scarce resource.
Soils are Sandy Loam with good drainage. Can I design the slab with a little more gravel/drainage or add another feature that would keep it stable while unheated for the first winter in Northern Wisconsin?
I designed a FPSF that would not have insulation under the slab as outlined in the HUD guide.
Thanks
Christian
Replies
https://www.huduser.gov/publications/pdf/fpsfguide.pdf
In order to survive the first winter, you need to design as if it were (which it will) be an unheated structure.
For a cabin, I would think you would want it designed to be stable when unheated, regardless. things happen, power goes out, life changes and keeps you from your cabin.
This looks to me like it calls for insulation and the proper draining material (no fines)
You could try to shortcut and skip the insulation but the risk is if you end up with a cold, wet, winter, the loam in your soil could conduct water to a freeze-thaw cycle that heaves and breaks your new slab.