Slab on grade, zone 7, subfloor/hardwood Q
Hey, guys, gals.
Here are the facts:
1956 slab on grade 4″ , Costal Alaska, property drains well.
Stem walls all have 3″ new XPS, 36″ deep.
Slab has a few very small cracks.
Old vinyl removed, a thin layer of Black mastic remains, but not enough to create gaps or high spots.
I did a simple moisture test (6 mil plastic taped to floor for 2 weeks) this past summer in 3 different places. No moisture was trapped.
I have height problems. Not me, my ceilings. slab to joists is already under 8′.
I have 5″ acclimated fir flooring. 16’ers so no joints.
My slab is pretty flat. I think its good for 3/16 over 10′
5/8″ CDX glued/nailed to the slab. Felt over that, nail down flooring.
Vapor barrier for insurance? Perhaps Taylor adhesive under the plywood? Plastic under it, and no glue? plastic over the ply, under the felt?
Materials are sometimes had to get up here. I may not have access to T&G ply. Thoughts? I don’t want to deal with a ton of un-level joints in the subfloor.
I had considered 1/2′ rigid foam and 5/8″ sleepers to aid in the warmth of the room but I’m not convinced it’ll make that much difference. Thoughts?
*Best I can tell, its a 3-4″ slab, then 1″ of maybe rock wool, then gravel/ag, dirt, no rebar.
*Ive been told the mastik acts as a vapor retarder too for what its worth.
It’s time to order the materials, yesterday!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part