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.
Spencer
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Replies
Spencer,
Your suggested method won't work, because your tapered sleepers will dig into the rigid foam -- they will dig in gradually, as you load the floor above with furniture and people walking around. As the sleepers dig into the rigid foam, your wall won't be level anymore.
Don't try to do too many things at once. Start by leveling your floor -- either by your method (sans泡沫），或通过拆除现有的每个现有托梁的现有底层地板和姊妹托托托托件。
Once you have your new level subfloor installed, you can decide how to insulate your floor assembly.
Martin, thanks for the reply. As there are 4 rooms I want to level together, sistering seems like it would be the better option. Thanks for the input!
What about leveling the floor as you add the new footings and posts?
And getting air barrier continuity across a floor plane is all about what penetrations you have to seal and linking your floor air barrier to your wall air barrier.
My experience is mostly in cold climates and we just have not had very good results trying to vent crawls by insulating and air sealing at the first floor level. And you will need a sort of "mechanical column" for whatever connections (plumbing) you need to protect from freezing.
Peter
Peter
I will be doing the post and beam work at the same time as the leveling, it just strikes me as being easier to treat them separately. The existing joists are old round timbers and I mainly just want to support them mid span.
很可能会有一个机械室在大约4英尺高的爬行空间中央建造和隔热。这是房屋中集中找到所有泵和炉子的唯一途径，而您的观点将是皮塔饼。
Do you generally recommend spray foam on the basement/ crawl space walls? We have a field stone foundation and it seems like that approach would be significantly more costly.