I have a split level townhome built in 1979. Due to moisture damage in a few areas (sliding glass door, kitchen, and shower surround) I need to replace some subflooring. In the living room and bedrooms, there's 5/8" (I think)particle board on top of 1/2" plywood. In these areas, I plan to replace damaged areas only and in the end, will install some engineered hardwood and some carpet. In the kitchen & bath, the existing subfloor consists of two layers of plywood - 5/8" (I think) on top of 1/2". In these areas, I'm replacing the 5/8" top layer (due to existing vynil that won't peel up) and any damaged areas of the bottom layer. In the end, these areas will have ceramic tile with radiant heat. I know that current practice for tiled areas is to have 3/4" plywood subfloor with a 1/4" cement backer underlay. My question is this... From a tile perspecive, Is 5/8" on top of 1/2" equal (or superior) to 3/4"? Obviously, the total thickness is more, but does the extra layer introduce any problems?

I'm pulling my hair out trying to figure out the best way to build and install a utility closet in my basement to hide the sump pump. The basement isn't finished, but I'm putting in carpet, so I had the idea for the utility closet. The problem is that neither the concrete floor nor the overhead joists seem to be even. I understand that the studs must be plumb. Should I nail in place a cap plate and a bottom plate, knowing that they're not level, and then build a true squared wall for each side, and shim them in place (between the cap plate and top plate + again for the bottom)? I'm trying to wrap my noggin around this and figure out the best, or the least stupid way to do this? Also, (2nd question): Do the outside studs need to be nailed to the foundation wall, or just attached at top and bottom? Thanks, Scott