Re: hardwood floor height
Depends, are you nailing the floor down or is it a floating floor?
If you're nailing, then underlayment may be required if the subfloor is not thick enough to resist movement or hold a nail sufficiently.
If it's a floating floor, then you will be adding 6mil plastic vapor barrier, 1/8" foam sheet, then the floor is assembled over the top.
What does the flooring manufacturer recommend, because ultimately their guidelines are what matter.
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