Confirming Door Jam Dimensions for Thick Walls

Hey all,
We want to double check the dimensions that the door vendors are providing for the jam/jam-extensions for our exterior doors . Since our walls are framed, we have the option to use the drawings (image atch’d) or the actual wall. We will use the as-built dimensions, but aren’t completely sure where to measure.
1. From exterior edge of GWB to exterior edge of the rain screen
2. From interior edge of GWB to exterior edge of the rain screen
3. Some other points
Can someone help me understand what measuring points we should use to check this?
Thanks All!
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Replies
Ideally, door jamb should be as wide as wall but door jambs are generally made for 2x4 or 2x6 walls, not for 2x6, plus thickness of exterior insulation and rainscreen. Not sure a door company would even make a custom door with such a wide jamb but if they did it would likely be very expensive. In the past, I just get a door for 2x6 wall and add extension jambs myself in the field.
AGoldstein - Thanks. I have a millwork shop and a couple of building supply stores providing me with quotes. The millwork shop, I believe, is going to order the door slabs and then build out a custom width jam for the exterior doors.
I thought of adding extensions it just seemed like the connection would be pretty sketchy - a 2 or 3 inch piece of wood attached on the short width of the jam.
AGoldstein, if you haven't tried asking for thick jambs, you might be surprised--they are readily available here in the northeast but you have to ask for them. I have ordered them up to 11 1/4" deep; that was the most they would go.
idahobuild,
Just like on interior doors, the jambs and head cover the area from the inside of the trim on both the exterior and interior.
So in your case, as long as you are planning to butt your siding against the exterior door trim you would use what you identified as #2. If however you are mounting the window and door trim on your siding, you would have to account for that in the increased depth required.
If you used what you identify as #1 you would be left with a gap revealing the ends of your drywall you would somehow have to cover.
As A.Goldstein said, it may be easier to get standard jambs and make your own exterior extensions.
Malcolm,
The windows are attached to the bucking (see Window Detail atch'd). The siding will butt up against the door and window trim and is attached to the rain-screen battens.
So, if I am understanding correctly, the measurement is from (see yellow arrows on DoorJamMeasurement_v2.jpg -- atch'd):
Point 1 - Exterior Side of the interior trim
Point 2 - Interior Side of the exterior trim
Note: Air and WRB details omitted from drawing for subject clarity.
Thanks!!!
Idaho, yes, your #2 option, or what you note here in yellow, is what I would order to. Round up to the nearest 1/16".
Michael - Thanks.
P.S. For a second there I thought that I put the wrong name in when I replied to Malcolm. Then, I noticed you had replied. Thank you too Malcolm!
Haha, yeah, sorry to butt in!
Hey Michael - When I checked the measurements of the as-built, RO, wall thickness one or two of the door's thicknesses differed from the right to left side of the door by about a 16th. Would it be better to order it bigger and shave a side down a bit or smaller and shim?
Does that make sense?
Thanks.
Yes, that's very common. Stock jamb sizes are 1/16"-1/8" deeper than the nominal wall depth, and that's what I would recommend. You can caulk or roll the casing to hide the gap. Rolling means the casing isn't perfectly flat on the face. If the jamb still comes up a bit short of the wall thickness, you can carefully cut out the face of the drywall where the casing will go. When casing has to be perfect, I have used other methods that involve trickier carpentry, but I can explain them if you'd like.
Before all that, try holding a length of two-by material on the face of the drywall and whack it with a hammer, and run your hammer around the exterior sheathing--sometimes one or the other just doesn't get fully set into place.
idahobuild,
Go with the larger dimension. When the drywall is in and taped there will be a slight bulge at the seams. A 1/16" variation in the RO is in the weeds. You won't notice it when you trim - unless the jambs end up too small.
It's easier to fix the appearance of a too-big door jamb (caulk, drywall mud, etc), than it is to fix the appearance of a too-small door jamb.
Thx all.