I'm building a rec room and first thing I'm doing is placing 2" foam on the floor and walls. once i have all the seams sealed up , I want to put 1/2" or 5/8" T&G plywood down. Can I simply use adhesive to make the floor stick or do I really need to fasten it down to the concrete with screws? Thanks for any help.

Concrete floors are not as flat as you might think. Laying foam down and then T&G ply will end up with a bounce when you walk in some areas. It would be better to install pressure treated sleepers every 24" screwed and glued to the concrete and then put your foam between the sleeper. The ply can be screwed and glued to the sleeper.

I agree to the above post, but I think you should put a layer of plastic over the sleepers and concrete and tape the joints.

If you do not seal out the moisture, I think that mold will form under the foam and cause a bad situation.

You could put the plastic under the sleepers too, but then you have to rely on anchoring the sleepers to the floor with adhesive.

Good luck- write me if you have questions