how to shim window casing

Hello all,

I'm just starting to install my window casings. My wall is out of plumb. My window is flush with the sheetrock at the top of the jamb and the jamb is set in almost a half an inch at the bottom. How would you install the trim ? Shim the window jamb or build the jamb out and then shim behind the casing/wall? Thanks

 

First of all, I'd figure out if there is a reason why there is such a difference. Walls are normally a consistant thickness all the way around a rough opening. So unless you have lathe and plaster walls or there is some other weird reason why the jamb would be that far out of whack, I'd check to see if the window can be pulled in more on the bottom. If it's been foamed in place, the foam would need to be cut in order for the window to move.

If it's not possible to move the window, then you would probably need to hold the casing up where it will go... draw a pencil line around it... and maybe remove some of that drywall inside the pencil line... score the pencil line with a utility knife and remove some of the drywall inside the line by tapping it with a hammer until it crumbles. Obviously be careful that you don't crack the drywall where it will show. The object is to create a taper so that the trim will sit flush with the wall on the outside, and still tip in and meet the window without "rocking" on the corner of the drywall that sticks out beyond the jamb.

When you cut that miter, it will actually be a compound miter. You might benefit by reading other similar posts on this topic, like this one.