I'm converting an existing screened porch (New Hampshire) into a 3 season room. The floor is 5/4 X 6 decking which I need to cover and finish. I only have 1 13/16 to play with until I come flush with the existing threshold. I was thinking about 1" thick foil faced rigid foam directly down on that decking and then covering that with 5/8 T&G plywood. That would leave me somewhere around 3/16 or 1/4" for indoor/outdoor carpeting or some other finsh. Here are my questions:
-do I need "sleepers" to keep that foam from crushing or can I just screw the plywood down through the foam?
-if I do need the sleepers, how would you space them?
The floor is 16' across the joists by 10' deep.
Thanks for your thoughts.
Supposedly, you just lay down the polystyrene foam insulation, then the top flooring and screw it into the joist. I've only used it under durarock and tile floor. I don't know what kind of effect it might have with a plywood top, and a space that large.