For basements, the usual for walls seems to be a pressure-treated bottom plate attached directly to the concrete floor.
I'm using a (waterproof) subfloor material that channels water to the floor drain. The perimeter concrete walls will be sheathed in XPS styrofoam (any seepage through the concrete wall should drain to the floor rather than through the XPS). The manufacturer of the subfloor (OVRX Barricade) indicates that walls can be built on top of the floor, but it is a floating floor so the idea of building finished walls on top of it seems counter-intuitive...so I'm going with the assumption that the walls shouldn't be built on top of the floor.
Is there any reason not to place the bottom plate for exterior walls on top of 0.5" XPS styrofoam rather than directly on the concrete? The idea is to cut the foam into 3.5" x 4' lengths (separated by small gaps to allow moisture flow). Without the gaps, moisture may collect behind the wall with nowhere else to go. With the gaps, moisture could flow under the subfloor and to its final destination (the drain).
Makes sense to me...but I haven't seen anyone else doing it. Thoughts?