How thick is plywood subfloor and can I reuse old carpet padding? ... for hardwood install?

Question

I have just removed the carpet in a bedroom and discovered that it had been installed over a plywood subfloor. Since this bedroom is on the second floor, is there a minimum thickness for the plywood presuming that it was placed directly on the joists?

The padding from the old carpet appears to be in great shape. Would placing felt paper (on top of the padding) followed by 3/4" hardwood floor be ill-advised?

Thanks

Answer 1

Usually there is a layer of 5/8 plywood put down on the joists for a sub floor.  They put a second layer if it is to be carpeted or tiled like in a bathroom.   This equal ls the thickness if you were to lay a hardwood floor.

You want to remove the top layer of sub floor and put the hardwood directly on top.  There is no padding under the hardwood.  With these multiple layers all of the floor surfaces are reasonably equal and not give you something to trip on.