We recently purchased a lake house and found moldy framing and drywall. The removed drywall had a black backing on it, similar to felt paper. This part of the wall is sub-grade with wood (gc 2x6’s) behind the drywall. It’s a split-level pier and beam house. I would like to replace the drywall with OSB or something more water tolerant, but am wondering if roofing paper would be appropriate behind it.