I just pulled the sheetrock off my basement walls and found that the framing on the outside walls was done with 2x2's. I was under the impression that they should be 2x4's. Can I nail 2x2's on top of current framing making them 2x4's? Or does it not matter?
Provided the walls are perimeter walls along the foundation and only serve the purpose of holding up sheetrock, they can be 2x2's. It isn't all that sturdy for hanging TV's and such though. I always frame basement perimeters with 2x4's because I prefer it. Interior walls within the basement should never be anything smaller than 2x3.
You won't gain significant strength by adding a 2x2 to the existing 2x2. The only benefit would be additional room for insulation.