How to build a basement partition wall?

I am adding a basement bathroom to my house. The floor is poured concrete, and will be breaking out a trench to install drains for the toilet and shower.
I plan to lay pressure treated 2x4 sleepers (so the longer side is on the concrete) nailed into the concrete, covered with 5/8" T&G plywood, then sheet vinyl. I want to leave a gap to keep the finisheed floor warmer, and to allow a the ability to vent out under the plywood should any dampness creep into the floor.
Due to the basement plan, I only have to raise one non-loadbearing partition wall to make the room.
Should I build the wall:
1) On top of the wood subfloor to the ceiling (makes it easy to attach drywall), or 2) From concrete to ceiling directly, and place the plywood inside the walls (will need another piece of wood at the wall base for drywall attachment)
Dave nospam protected address
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I have a couple of suggestions: 1. Use 3/4" plywood, if you must use 5/8" space the sleepers at 12" on center. the 5/8" will be a springy floor.
2. Is there a vapor barrier under the basement? If not you will need one below the new sleeper to prevent water vapoer from getting into your new framing.
3. I don't see a problem with building your wall on top of the new floor. I would run a sleeper parallel to the wall.
Good Luck
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