Tools used on this job.
Drywall proud of door jamb.
If not i think your best option is going to be to build the extensions proud of the wall and then bring them down flush with a power planer or belt sander.
I have a homeowner who has window and exterior door jambs that extend past the drywall by about 1 1 2 inches.
These jambs span from one side of the wall to the other.
Doorjambs are designed to fit standard width walls made out of 2 by 4 or 2 by 6 lumber plus a layer of 1 2 inch drywall on each side of the wall.
Sometimes slight misalignment of framing heavy tape joints and other variance means that you d shift the jamb slightly from center of the wall for a better outcome.
It s important to know what to do in less than ideal situations.
The door casing is nailed to the jamb and to the wall and covers the space between the doorjamb and the wall.
It is an old house 1920 s 2 story that had 2 layers of lathe and plaster on it.
Hang the doors after painting after hard flooring and before carpeting.
As an amazon associate i make.
Is there any possibility you can adjust the window installation to bring the jambs flush with the drywall or at least parallel to it so that the extensions will be easier to make.
Watch a simple way to build and install your own wood trim that also solves a common problem with drywall that extends too far past door and window jambs.