With the success of the plumbing last night, the next step in the process will be to add the subfloor. We decided to go with OSB type sheets for a couple reasons. One being that it is strong, light and readily available. The other is that it is dimensionally stable and tongue and groove. When I did the subfloor in the laundry/bathroom downstairs I used regular 3/4″ plywood and it gave me a ton of problems with swelling at the seams because of the moisture change from the department store, to outside, to inside. It didn’t get wet but felt it swelled enough to have to belt-sand the edges down before the final flooring went in.
For total strength over the 2 foot span center beams, we went with two layers of 3/4″ OSB. The first layer was laid perpendicular to the joists so that the seams landed on a stud. The second layer was ran perpendicular to that so that no seams lined up with one another giving it the least amount of flex overall. The first layer was glued and 2-1/2″ screws and PL subfloor glued to the joists. The second layer was glued in a “Z” pattern and screwed using 1-5/8″ screws.