I'm working on framing a wall where a sliding glass door once sat. In retrospect, I believe I should have used 2x6 lumber to frame the wall, rather than 2x4. While one side sits perfectly flush with the existing wall, the other side (shown in the picture) sits about 1.5" back from the existing wall.
Can I screw 2x4s horizontally to the framing to "shim" the drywall into the correct position?
Also, these are several different things hanging on the existing wall (some sort of cement shingle, tar paper, foam board, etc) Do I need to remove all of these prior to hanging drywall, or should I leave them as extra insulation?
Here is an up close view so you can see the gap between the framing and the existing "wall":
Any advice is appreciated.