I've searched and cannot find the particular question I'm about to ask. I'll be installing 3/4" T&G OSB Sturd-i-floor over 1/2" OSB subfloor. I realize on the butted ends and the walls I'll need to leave a 1/8" gap, do I need to leave a gap where the Tongue meets the Groove or do I make those tight?

I'll be installing 3/4" solid hardwoods to the OSB.

Do I also need to put felt between the subfloor and the underlayment? I know I need to do it between the underlayment and the hardwoods.

Thanks for the help.

I figured this one out. Thanks. Basically, I'd leave a 1/8" gap around the outside and on the butted joints, but the tongue should go into the groove. I also found another topic while looking for something else that stated I do not need to put a layer of felt between the subfloor and the underlayment.