Those who read my other posts know that I am in the middle of a crawlspace-to-basement conversion project. A few days ago I placed the concrete for my retaining wall footing (the retaining wall is L-shaped and runs the length of two adjacent foundation walls. I screwed up on about a 10' wide section where the footing is about an inch too high. My plan was to place a 3.5" floor slab. If I keep that same floor level, the slab will taper up to only 2.5" over that 10' section of wall footing. Here is a sketch of what I'm talking about: My column footings have a 3.5" curb in the center where I am planning to screed my floor slab level with. I'm real nervous about tapering up to 2.5" though. My question is would this be a real bad idea to have part of the slab go that thin? The other option I'm thinking of is to raise the finish slab surface up a 1/2" and add thickness to my column footings with a 1/2" of thinset to match the floor. That would give me a 4" slab that tapers to 3" in that section. Any thoughts on this? Thanks.