I was just about to start building/installing window casings. When I measured the depth from the window to the front of the drywall, I noticed one side is 3.5" while the other side is 4". I also noticed I have a big gap in the drywall around the window frame. one side the drywall is tight against the window frame (like I would expect to see). The other has about a half inch gap between the drywall and the window frame stud. I was trying to figure out how to build a window frame with this type of problem, or if there was a way to fix the problem before doing the trim work. I tried to look in the gap, and I didn't notice anything off hand that would be in the way of the drywall... I have heard about sometimes studs warp in the winter, and I'm not sure if that's what this is (I haven't looked at it in the summer yet). But if it is, I don't think I would want to frame it as is now, and have it crack apart in the summer, and vice versa. Not sure if this makes sense, or what other info would be helpful.