Foundation wall, mainly
Zone 8, Fairbanks, Alaska. 14,000 HDD (at least as recently as the early 70's. I don't know any more; seems more like 10,000.) Part of this design was shamelessly stolen; the rest was tweaked to my "specs", for various reasons.
The first photo is a cross section of the foundation wall and footer, with the "general wall" above it. No, this will not be constructed quickly, and no, it won't be cheap. I know the soil will only take 17 psi and that 25 psi foam should be beyond adequate for bearing under the footer, but I can't get myself to trust the foam itself. (Moderate seismic activity.) Thus, I'll be spending $10/sheet extra for the 40 psi stuff.
One question I have is whether or not I need the extra 2" of foam inside the ICF block, in addition to its own 2 1/4" and the 1 1/2" EPS I added.
As for the walls, that design was also stolen and tweaked. The 1/4" plywood on the exterior (on 2x4) is my idea, as I don't want to dense pack cellulose into a wall with just a WRB holding it in; another individual builds that way here, and I guess it works. It will be painstakingly drilled w/ a million small holes to keep its permeability high.
The 1/2" plywood (on 2x6) will be an air barrier (gooed and taped) and vapor retarder. It will also have dense pack cellulose in it.
Another thought I had is that perhaps the treated lumber will shrink less than the KD wood above it, so maybe I'd trim the treated stuff so any shrinking does not pull the plywood off of the KD wood. Over-thinking again?
The Benjamin Moore vapor retarder primer idea is probably not a good one. I don't want to trap moisture between it and the 1/2" plywood, so it will probably not be there.
So shoot. Any suggestions?
Posted Feb 4, 2011 1:48 AM ET
Edited Feb 4, 2011 6:43 AM ET
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