I am trying to figure out the best flooring options:
I need to keep thickness down. I found 3/8" fan fold, polystyrene, R3.6. I was planning on liquid nailing this down to the metal (Rustoleum Enamel, 2 coats) and then using 11/32" sheathing plywood on top of this. All of the metal is sealed from the outside.
I was curious to figure out how to put a vapor barrier under the insulation while still using the liquid nails to firmly secure the insulation and subfloor. Do I need a vapor barrier here? I read about sweating but the polystyrene is not affected by moisture.
Do we think that 11/32" sheathing plywood is too thin for subfloor? I MUST keep the insulation, subfloor, and flooring under 7/8" in order to have enough headroom.
I do not want to screw in subfloor in an attempt to mitigate any thermal bridging throughout the interior of the bus.