Rigid insulation under subfloor, over joists
We’re renovating our 1940s timber framed house here in Ontario, and I’m trying to solve both an insulation and framing issue at the floor. The floor is about 6” out of level across various dips and humps that will be addressed structurally by new footings and posts in the 4’ crawlspace. I plan on leveling the floor with tapered sleepers and a new layer of 3/4” ply on top. My idea is to lay a layer of 1” ridgid insulation down on the existing subfloor and then apply the sleepers and ply over it, screwing down to the joists through the insulation. This would provide a solid air seal between the house and unconditioned crawl space, and provide as easy plane to tie in the MemBrain I’m using on the interior. Running full sheets of ridgid insulation saves tons of time over the cut and cobble approach under the joists and seems like a more fool proof method. Has anyone every tried this? The flooring will be nail down hardwood, if that matters.
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