Originally Posted by dclynch
What kind of shower wall are you going to install? If it is a fiberglass surround, you should check to see how it is supposed to fit. The gap might be appropriate.
If tiling, I would shim out the studs so that the backer board will clear the lip of the base. You have to use a cement board now, greenboard is no longer up to code. Hardibacker is widely available and not that much harder to work with than greenboard. A vapor barrier (poly sheet) goes behind the backer board and overlaps the pan edge.