"Augustine" wrote in message
ups.com...
It's above grade and I thought of a poly sheet as a vapor barrier
(Vapor Lock).

I'm trying to minimize increasing the height too much, and I was
thinking about 1/4" or 3/8" thick. Are such thicknesses feasible?

What are you putting on top of the subfloor? 3/8" is not much to nail into
for a real hardwood floor. For floating floors, then yes.