We have 2x4 studs with drywall and 1"-1.5" of exterior insulation and vinyl siding on outside bringing the total wall thickness to about 6".
Marvin Elevate French Sliders (wood/fiberglass) has 2 jamb sizes 4 9/16 and 6 9/16. The latter is too wide and the former needs an extension jamb.
Supplier suggested extension jamb on the interior as this looks better but everyone always say don't fuss with extension jambs, get a jamb that covers your whole thickness.
He said I could do custom jamb size but sounds like the piece arrives separate from the door. I'm not sure if this has any bearing on longevity.Here is a video on my wall condition: https://www.dropbox.com/s/cn7olfo8xqo1h9s/20221006_081122.mp4?dl=0
What should I do? Go with suggestion of 4 9/16 and add extension jamb on interior side? This is a 15 week lead time wait and don't want to mess order up, thanks for any guidance!!
This question should be answered by your installer, not you. I also think you are calculating it wrong. Your jamb is from the nailing fin to the inside frame of the window. Vinyl siding is not part of this equation. I'm not sure about the 1-1 1/2" insulation as that is not typical in California (my area but it sounds like it is also on the outside of the fin), so I would rely on your installer for the final decision.
Do a a custom jamb size if available or install a jamb extension kit the exterior side. Don’t do it to the interior.
@toddinmn So the exterior is fiberglass and the extension jamb would be wood against fiberglass. Won't it look better on interior wood agains wood? Is there a reason why exterior extension jamb is preferred?
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Interior door jambs don’t look proper and can limit the swing if the door.
@toddinmn ahhh that makes sense. Mine is a French Slider though. Will extension jamb be OK then on interior?
Yes it can be done and should look ok if executed properly.
@toddinmn thank you!!
Good feedback Todd. Nailed it.
I have same situation on my house, but have 3" of exterior insulation. I attached nailing fin to the sheathing where the air/water barrier plane is located, then made custom extensions on the exterior. It allows the use of a standard frame size and provides good support for the sill. I did have to add a trim at the sill. It depends what your sill condition is.
Complex install @Seabornman , but if you detail it out as you mention, very sound and certainly makes for a tight and insulated shell. What window did you put in the holes to go with that R-30+ wall?
@East Bay 10 said. The foam will be outside the flange typically. The window protrudes 1-3/32" beyond to butt against 1" foam w thin stucco. The jamb measurement is "inside" the flange. Most likely 2x4 wall if this is an older home but the jambs can be easily extended at install. Have your GC or installer look at the site conditions before ordering.