As I mentioned on another thread, I am preparing to finish my basement. I am considering the following subfloor stackup:

  • Existing Concrete Floor
  • Delta FL Vapor Barrier
  • 1" XPS
  • 5/8" Plywood (Tongue and Groove)

The finish flooring will, most likely, be vinyl plank in the living areas and ditra/tile in the bathroom.

I have several questions:

  1. Does this subfloor stackup look reasonable?
  2. Can the Plywood be left floating in the living areas?
  3. Should the Plywood be Tapcon'd through the XPS to the existing concrete in the bathroom?
  4. Should the partition walls be built on top or next to the built up subfloor? (see sketch below). In either case the base plate would be fastened to the existing concrete floor.

In the sketch below, I've shown "on top" as A and "next to" as B. If A is used, to the left would be an unfinished utility room with a dehumidifier to pull any moisture from below the Delta FL. If B is used, any moisture below the Delta FL have to absorb back into the concrete or into the base plates (which would be treated, of course). The exterior stud walls are in, so B will be used around the perimeter of the basement regardless.

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Thanks in advance for your replies!