Only shim the top jamb if you re working with a 3 ft wide door and the top jamb arrives bowed from the factory.
Installing new interior door jamb.
Screw the hinges onto the correct side of the jamb.
Once you are satisfied with the fit of the door remove it and apply several thick beads of silicone caulk to the bottom of the doorsill.
If you have more than an inch to remove take half off the top and half off the bottom.
Unless you are installing a prehung door you ll need to trace the outline of the hinges on the jamb and cut an indentation using a router or utility knife.
Any changes to the door frame should be made before installing the new door.
Place the door in the jamb and fasten it to the hinges.
And on new homes and additions walls can compress as they settle and push down on the top shims causing the jamb to bow down.
Remove the old door and cut the new door down to size.
If you have more than 3 16 of an inch to remove you can use a circular saw to do so.
Once again take care not to damage the frame or the wall during this step in the process.
Check the fit before installing a new door and enlarge the opening as necessary.
Caulk underneath the spots where the bottom of the jamb and brick moulding will be.
If the holes on your new hinge plates don t match the holes in the screw holes in the door jamb drill pilot holes for the new screws.
If you re not steady with your saw you can use a straight edge as a guide.
Pry the side jambs away from the studs and then pry down the head jamb.
It s not always necessary to use shims on the top doorjamb the casing will hold it in place.
Hang the door in the jamb.
Allow the glue to cure and drill the pilot holes.
Go slowly and make a long clean cut.
Make sure it s tight and opening in the right direction.