I’m redoing this basement kitchen in a maybe 80 or so year old house. Basement walls are sandstone I think and have been covered over with a thin concrete (?) coating that is falling off the walls in places. Floor is concrete that was apparently poured long after the cabinets were in place as there is none under them. (Note the 1x’s that were attached to the upper half of the base cabinets, and that were holding up the upper cabinets–with nothing attached to the wall. Amazingly solid, too.)

My thought is to build new stud walls, covered with 1″ XPS–foaming around the XPS edges and joints to seal them–then drywall. Will also pour some concrete where base cabinets will go.

Several questions:

1. The new wall will be attached to the concrete and the ceiling joists so doesn’t need to be attached to the sandstone at all, does it?

2. While this is open, I’d like to seal the rim joist with XPS and foam but then am not sure how best to insulate/seal from there to the new basement wall, i.e. the 8-10 inch top of the old basement wall. Maybe an inch of XPS across the top of the old wall, then FG up to the ceiling joists and between the joists?

3. I’ll use pressure treated wood for the base plate. Should I also use it for the studs?

4. Anything else you think I should pay attention to I’d be happy to hear about.

Many thanks!