I am building a small addition over a ventilated (unheated) crawl space. I was considering gluing down the sub-floor (5/8" plywood) to the 10" joists but what about the vapour barrier? Can I glue the 6 mil poly to the joists and the plywood to the poly, or do I forget about the glue? What kind of glue would I use? Is the cartridge type construction adhesive OK?
Answer:
There isn't a whole lot of sense in putting in the poly in the first place because insulating the floor will not give you a 4-seasons room with any amount of comfort. If you want to do it right, create a crawl space under the floor, insulate the walls and floor of the crawl space and heat it a bit.
