I’m planning on adding rigid foam insulation to an exterior gut remodel.
I believe I will adding OSB, 2″ of foam, 1×4 furring and the fiber composite siding to the existing 2×4 frame wall.
Even if I purchase a 2×6 pre-hung door with a 6-9/16″ jamb, it will be short of the new wall. How should I solve this?
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At the risk of being either "Captain Obvious" or "Oblivious":
For an inswing, size the frame depth to match your OSB face under the foam. Place a good membrane over the OSB and under the foam that you can connect to the door jamb with really good tape. Trim as an "innie".
I think I'd resist trying to bring the WRB around the edge of the foam and to the jamb in the form of a tape or ? since the foam will move and the OSB layer is a more reliable plane to air/weather seal to.
Is this even close to what your asking?
Just make sure that the wall thickness doesn't interfere with the operation of the door, which should be able to open fully. If you are installing an innie door that swings inward, you shouldn't have any problems. Outie doors may require a "frame-within-a-frame" assembly; for more information on this approach, see Windows and Doors in Double-Stud Walls.
Thanks. That makes more sense. So it seems I should stick with a 4-9/16" jamb pre-hung door.
I was planning on keeping with an in-swing door. So it seems like I'm in good shape.
Building a frame within a frame isn't much of an option without reframing the doorway. Its already tight up against a window, so the problems would get much worse, unless a dropped the door size to a non-standard width.
I guess my plan will now be (much like Albert's suggestion)...
"Standard door jamb" of 4-9/16" - 4.56"
1/2 Drywall - .5" + 2x4 - 3.5" + OSB - 7/16" = 4.44"
The jamb will extend 1/8" past the OSB (if flush with the drywall on the interior). I can tape or butyl flash this to the WRB on the OSB?
After that, I will have 2" of foam up to the jamb edge. When taping the foam do I tape this back to the original jamb, or wait for the jamb extensions to be applied?
After that, I assume I attach furring over the foam edging flush to the jamb extension, and then my trim pieces can go flush against the furring. I plan on doing fiber cement up to the trim, not over the trim.
I appreciate the help, I'm extremely green to this green building....
Optionally... I think I can order custom width door jambs.
I'll have to check with my door supplier. If I do that, can I tape or flash the OSB to the jamb, then put foam on, then tape that to the same jamb? Or would I be creating a problem doing that?