Cold climate basement subfloor questions
I’m finishing a 400 sq ft section of my basement to be used as a general purpose rec room and TV area in our home in Winnipeg, Canada. Our winters are extremely cold and dry but our summers are quite hot and can at times be humid. In 15 years we’ve never had water issues in our unfinished basement other than very short-lived signs of moisture “darkness” on the concrete floor in times of summer high humidity (especially if the central air conditioning had not been left running).
I want to insulate the floor but I’m concerned about moisture and headroom. Headroom between concrete floor to the bottom of the floor joists above is about 7′ 6″ except where there are beams and ducting where the headroom is only 6′ 9″. I plan a drop ceiling everywhere except where the beam/ducting is located and will probably drywall that.
There is so much contradictory information but I believe the best option is to stack up poly, then XPS, then 5/8″ T&G plywood (tapcon’ing the perimeter sheets as a minimum) followed by the finished flooring (planning for carpet to improve acoustics).
Because of the headroom (and concerns about altering the stairway and adjacent doorways, etc), I’m considering using 1/2″ XPS under the plywood. Is that acceptable or do I need to go 1″? 1/2″ doesn’t seem like much but every bit counts.
Do I have to be concerned about the moisture I sometimes see on the concrete floor on hot, humid days in summer? This might only occur a handful of days in a typical year. If so, should I lay down a dimple product (e.g. Delta FL) under the XPS? That of course would further hurt my headroom and I’m not sure if it helps or hurts my problem since it will actually allow air to get to the concrete?
I’ve also read that I should avoid gluing the XPS as mastic can promote mold. True?
Any other advice is appreciated.
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