How do I insulate outdoors sauna floor?
Am building an outdoors sauna on a limestone skid foundation.
This is the layup plan from the top down.
(Floor box construction)
Top layer of 3/4 Plywood
2 x 6 non treated floor joists
Insulation fiberglass with vapor barrier under 3/4 ply
Poly vapor barrier under the fiberglass
Bottom layer of 1/2 plywood seals box
(Floor box sits on)
Treated 4 x 4 skids sitting on
#57 limestone compressed 3 inches deep
What do you think about the poly between the insulation and the bottom layer of ply nearest the limestone foundation?
Will it block ground moisture from getting into the fiberglass? Or will it hold moisture in the fiberglass?
Other option is to do away with the fiberglass and bottom layer of 1/2 inch ply , leave it open and use hard foam insulation for the floor. But I don't see any foam that thick. Usually it is 1 inch or so. (In the past when I tried hard foam on an RV I had problems with it falling down after being glued in place.)
Thanks for any help with this topic.