First, I may have my terms wrong. I don't know which level is on the bottom (underlayment or subfloor) of a floor. We added a level to our house. It is ready for drywall and floors. The contractors put 3/4" tongue & groove plywood down on top of the floor trusses. Floor trusses are 24" oc. They glued and nailed them in place. Currently, when I walk on it, there is very little deflection. Do I need to add anything on top of this for solid wood T&G floors, or can I nail right into the flooring as is? The inspectors office declined to comment. Thanks.

In the course of a kitchen remodel in my 50's or 60's era home, I see that my subfloor in that room is a double layer of 5/8" plywood. There is tar paper tacked in between the two layers of plywood, and there is tar paper glued to the top (linoleum-type tile was glued on top of that). I am going to replace the top layer of 5/8" plywood, cause I don't think I could scrape the gunk it off, as quickly as I could lay down a few sheets of plywood. (Yes, the second layer needs to be there to make it even with other areas of the house and kitchen, and no, I can't just lay the finish floor on top or preexisting finish floor; there are too many layers of finish floor piled up already by previous home owners) Questions: 1) should I replace the tar paper separating the two layers of subfloor? I can't imagine why they did this, except maybe to reduce wood-on-wood creaking. 2) I plan to use 1/4" plywood as underlayment, on top of the 5/8" that I lay down. Should I also replace the tar paper above the second layer (under the finish floor). Can't imagine why they did this, except maybe as a type of underlayment (i.e. maybe they didn't have 1/4" underlayment back in those days). Thanks in advance. I always appeciate the advice I get from this forum. Aaron