I have a 1/2 inch plywood subfloor. 5/8 inch particle board on top of that. I plan on installing 3/4 solid hardwoods. I am going to rip up the particle board and put down plywood. I am debating between 1/2 inch or 3/4 inch plywood. Can either be used? I may end up going with 3/4 inch because it will get my floor to the height I need it to be. My real question is, what kind of plywood?

CDX or BCX?
Tongue and groove or square edge?
Do I butt the plywood sheets right up to each other or do I put a space? (how much of a space?)

Thanks!

Carl

1/2 is fine. leave 1/16 between sheets

We use cdx and i would use whichever got my floor to the proper height

Square edge for me

Since 3/4 inch will give you a flush fit to adjoining floors, spend the extra loot. Leave up to 1/4 inch between sheets to avoid any potential squeaking if the sheets rub against each other from vertical flexing of the floor system. This will also allow for a little expansion of the sheets during higher humidity seasons, although this is minimal with plywood in a controlled environment.