Is there anyway to attach pics here? Would like to show my sub floor. Thanks

Does your sub-floor have diagonally laid planks? And are not tongue and groove?

Yes, the 1st floor and it's also very level. I think they're 1x4. Theres a little spacing between them. They are not tongue and groove. That floor is pretty solid.The 2nd floor(which was added on) planks are 1x6 I believe and are straight with no spacing. That floor is slightly uneven in one or two locations. It's not the same type of wood as the first floor.Thanks a lot for the help.

If you have a good sub-floor, why are you adding a layer of plywood?

They had dogs that shit and piss everywhere. We gutted everything and disinfected/cleaned several times. Smell is gone but there a very very slight hint of it in the sub floor not really even noticable to some. We think the ply may help seal it.

Cover the sub-floor with Aqua-Bar waterproof Kraft paper. If you want so seal it before, apply Universal Seal, shellac. You will need to check the floor for flatness, set nails and sand high spots and build up low spots. The T&G and floor finish will block smells.

Thank you so much. So the shellac, then the kraft paper the the hardwood flooring?

Also that not the exact name of the shellac you just mean a general sealing shellac?

Zinser makes different shellac type sealers for sealing pitch in knots to covering fire smell or pet odor before painting. You can find white or clear. Universal Seal may be the best. They come in a spray can, quarts, or gallons. 400 square feet per gallon. One coat ought to do it.

Thank again. What do you mean pitch in knots & fire smell?

Fire smell is hard to get rid of, but shellac seals it. Pitch can start to come out and spoil a good paint job. Shellac will seal problems.