I have a wall that is measured at 4-1/4" thick (standard 2x4 with 3/8" drywall on both sides). The door jamb is standard 4-11/16" wide, which leaves an extra 7/16" or nearly 1/2 an inch to play with. What's the best way to compensate for this difference?
I'm thinking of the following options:
not worry about it. The slope in the window casing from the extra 1/4" on either side won't be that noticeable.
back the window casing with extra 1/4"-thick material, bringing it to the level of the door jamb
route a 1/4"-deep channel the width of the jamb in the window casing trim
Any other options?
The question is similar to this question but might warrant a different answer:
Use the extra width to properly hang the door . . . there is no need to disassemble the replacement door jamb.
Temporarily hang the unit in its final position. Use complementing wedges at the upper corner to position/secure the top jamb between the jack studs, and complementing wedges at the top and bottom of the side jambs to secure the each of those.
Adjust the wedges such that:
the hinge pins lie along a vertical line that is plumb in both directions (this is the key to a door that will remain resting at any angle)
the door closes uniformly against the door stops
there is a uniform gap between the door the jambs, about a nickle's thickness
the door operates freely
Scribe all 6 edges of the 3 jambs relative to the sheet rock
Label the wedges for ease of final install
Remove the unit from the rough-opening, set it on saw horses
Trim the jambs to their scribe lines (all 6 edges of the 3 jambs) using a power planer (or as @Tester101 commented, with a hand plane or belt sander)
'Complementing wedges' are a pair of wedges with identical taper, inserted from opposite sides of the rough opening.
If you don't own a power planer already, here is a google search. I suggest a light weight model with carbide blades that auto-align.
The "normal" way to deal with this issue is to disassemble the replacement door jamb and rip it to the proper width. The ripping is best handled with a table saw or radial arm saw.
Then reassemble the jamb for installation.