I’m in northern IL (climate zone 5) and I am removing the old lower level slab in my 1968 bi-level. It heaved up in multiple locations up to 1.5”, probably due to a combination of the slab being poured on dirt and metal chunks (no gravel) and the exterior drain tile clogged and failed.

I installed new exterior drain tile 2 years ago and installed Delta-MS dimple mat on the exterior of the cinder block. I have had zero water intrusion problems since I redid the exterior drain tile and Delta MS.

Attached is a drawing of how I am thinking I should go about the interior details. Some things I am unsure of is:

1. Is R-20 combined good enough for the walls in front of the cinder block, or should I loose another inch of floor space to substitute the 1” for 2”XPS for a total of R-25?

2. A standard wall here would need something like Certainteed’s MemBrain on the interior side of Rockwool. Would I need that barrier when I install the framing and Rockwool in front of XPS foam board?

3. With dimple mat on the outside and XPS on the inside of the cinder block wall, how would the block wall dry should it somehow get wet? Is that even a concern in this situation?

4. I have enough dimple mat leftover to do the interior side of the block. Does it benefit me in anyway to use that in place of or in conjunction with any of the items shown in my drawing? I know some of the basement waterproofing companies will use a dimple mat on the interior of the wall to catch any leaks or moisture and direct it to the drain tile.

I have one shot to do this, and I want to make sure I get it right. Thanks in advance!

Brandon