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Extension jambs for in-swing doors on double wall construction?

user-1097504 | Posted in General Questions on

Our home has double 2×4 walls, 10″ thick rough frame. Windows were easy to find, they can be hung on the outer frame (we went with Serious 725 series). But we’d like the doors to open inward and are having trouble finding doors with such deep extension jambs. Any ideas out there? We are in central New Hampshire.

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  1. GBA Editor
    Martin Holladay | | #1

    Trim carpenters routinely make interior jamb extensions from pine lumber, drywall, or a variety of other materials. If your carpenters can't make jamb extensions, it may be time to find another carpentry crew.

    If you are installing in-swinging doors as "outies" on a double-stud wall, it makes sense to install the doors using a frame-within-a-frame approach, so that the walls don't interfere with the operation of the hinges and so the door can open fully. More information here: Windows and Doors in Double-Stud Walls.

  2. user-1097504 | | #2

    Hi Martin: Thanks for your response. I think maybe I wasn't clear what we are looking for. We'd like to hang the doors on the inside wall, so they swing all the way open to the interior. So we are looking for doors with deep enough and weather tight exterior jamb extensions, preferably offered by a door company without the cost of being customized. Maybe such a thing doesn't exist and that is why we are having trouble finding them?

  3. wjrobinson | | #3

    Without the cost? You're killing me. I like the honesty.

  4. GBA Editor
    Martin Holladay | | #4

    I don't know of any door company that will make a door jamb for 10-inch-thick walls without charging you for the custom work entailed by such a thick jamb. Most builders would just extend the jambs on the exterior with durable trim.

  5. homedesign | | #5

    This points to one of the downsides of Innie Windows and Doors
    Someone has to fabricate (off-site or on-site) a piece of air-tight and weather-tight Furniture.

    If I lived in Fairbanks Alaska... I would consider building Midi Windows.... like Thorsten Chlupp

    for most of us ... I think Innie and Midi windows are Not-So-User-Friendly
    Not-So-Buildable, Not-So-Affordable and Not-So-Durable

    Have you ever seen an Innie Skylight?

  6. GBA Editor
    Martin Holladay | | #6

    Another disadvantage of innie doors: detailing the sill. It's very hard to build a watertight sill extension, and all of that blowing snow will eventually rot your rim joist.

  7. homedesign | | #7

    Martin, have you ever looked at John Abrams sill detail?
    I Like the way that Abrams/Rosenbaum detail their outie windows and doors.

    Here is a "free" pdf for the John Abrams JLC Article

  8. dankolbert | | #8

    What we've done a couple of times is leave a larger RO on the inner wall, order the door with 6-9/16 jambs and attach 2" of rigid foam to the exposed outer wall around the door. Looks nice, seems to perform well, solves the banging door problem, uses standard dimension jambs. You can see an article I wrote that includes the detail (p.5) here -

  9. user-1097504 | | #9

    Thanks everyone! The doors salesman was able to find a 9.25 inch jamb from Thermatru, and he is working on some shop drawings to do weathertight detailing for that last inch on the exterior. We'll see what they come up with...

  10. GBA Editor
    Martin Holladay | | #10

    Dan and John,
    Both of the JLC houses you linked to have outie doors. That's the way I think they should be installed. If I understand correctly, Janet wants innie doors, and that is more problematic.

    Dan, it looks like your method is very similar to the one used by Rachel Wagner (shown in the FHB article I linked to). The doors are outies, and the inner wall has a larger rough opening than the outer wall.

  11. homedesign | | #11

    That's another great JLC Article
    I would recommend JLC Online Magazine to anyone interested in building High Performance Homes
    Of Course FHB Online is just as good ....but different

    I think there are more examples of Double-Stud Walls (AKA Turds) at JLC

    I think Taunton(FHB) is more in tune with the BSC Dogma....(Insulate Outside)
    "Don't eat your sweater"

  12. user-1097504 | | #12

    Just to be clear *why* we are looking for an 'innie' option on the doors:
    1) we want it to swing in (not out) so that we are not sweeping someone off the porch or steps
    2) we want it to swing in ALL THE WAY for eventual handicap access and because it is just plain nice for doors to open all the way!
    3) we want screen doors, especially on the set of french doors, and screen doors are cheaper to buy for the outside, to swing out.
    4) for weather tightness of the french doors especially, it seemed to make sense to have them out of direct weather a bit.
    Curious if our logic is misled/incorrect to begin with?

  13. homedesign | | #13

    Dan's Doors are Outie and they open in.

    when you say you mean a pair?
    Have you considered "Atrium-style" hinging

  14. GBA Editor
    Martin Holladay | | #14

    We all agree with you that doors should swing in. Study all the details we have linked to and you will understand that it's possible to detail your wall (assuming you get the rough openings sized correctly) so that an outie door can swing in and open all the way.

  15. wjrobinson | | #15

    Martin, the depth of a door sill is waterproofed below the sill, with the showing part mainly being a durable layer to tread on so to speak. I have used both ice and water shield and leftover scraps of EPDM roofing. and some ot the retail product sold for sill flashing and detailing. Many ways to keep the water out if built with such.

    Janet, Thermotru doors are jambed by a shop along the way to the retail supplier. What they make a good carpenter also can make as that is how they will do it at their shop too. You may not get a Chlupp level of E conservation but you should get a door that fits the rough opening. Except for half round jamb extensions we mostly fabricate extensions onsite exactly to what ends up being the whatever odd dimension of all the built up materials.

    Both ways will get the job done, sometimes factory jambs are modified just a bit onsite.

  16. homedesign | | #16

    Janet, when you say "ALL THE WAY" you mean 90 degrees or 180 degrees?

  17. user-1097504 | | #17

    Yep, gotcha. I guess the other thing is that the frame is built already. But re-working the inside frame as your drawings suggest may end up being more economical and durable than paying extra for the 9" jamb and weather tightening work so I will look into that. Lesson learned. Thanks again.

  18. dankolbert | | #18

    And if you're interested in energy conservation, don't get double-active French doors (meaning both doors can open) - notoriously difficult to keep air-sealed, much less water-sealed. Either go with a single door flanked by window(s) or at the very least get a single-active door (one side fixed, the other operable). As my friend Wes Riley says, the best window or door is still a lousy wall. Except he probably doesn't say "lousy."

  19. user-1097504 | | #19

    John: yes, ideally the doors would open 180 degrees so they are flush with the wall. seems like it shouldn't be so hard to do that, just because we added a few extra inches of wall (speaking as an amateur first time home owner and G.C.)! but as i said, i'm learning.

  20. Expert Member
    MALCOLM TAYLOR | | #20

    Janet, Another solution is to angle the walls in so you can still use standard jambs. This also allows the doors or windows to admit more light.
    An example from Patkau Architects:

  21. scrumper | | #21

    There's a saying about the weakest link - after building with a double wall you want to plonk in a couple of thin doors? If you want to maintain the integrity of the envelope and want it waterproof, how about building a vestibule? Deep enough that an inner pair of doors and an outer pair can both swing into that vestibule, neither onto the deck nor into the room. Have one set narrower than the other so they will not fold into each other.

  22. judycalistro | | #22

    Another approach would be to use wide throw hinges.

    If the door is not flush with the frame, is sitting back in a deep reveal from the face of the frame with or without additional obstacles created by applied trim on the face of the frame or a deeper reveal caused by a projecting wall, and the door is to swing 180°, then a Full Mortise Wide Throw Hinge may be used in hanging the door.

    Important in this regard is how to calculate the proper width of a wide throw hinge (rounded to the next higher whole number if result is not a whole number: e.g., 6", 7", 8", etc.)

    1. If the door is sitting inside a deep frame reveal with no other obstacles (i.e., projecting trim or wall), add the depth of the reveal (distance from the face of the frame to the face of the door) to the recommended width of hinge used under flush conditions. Example: A 6" wide (wide throw) hinge would replace a 41⁄2" wide regular mortise hinge (used under flush conditions) if the depth of the reveal is 11⁄2".

    2. If the door is to clear projecting trim or wall and the barrel of the hinge is not obstructed, then calculate as follows:

    (a) double the size of the door, (1 ¾ X 2 = 3 ½ )

    (b) subtract 1⁄2" if the door thickness is less than or equal to 21⁄4" or subtract 3⁄4" if the door thickness is greater than 21⁄4" (3 ½ - ½ = 3)

    (c) add for the additional depth from the face of the obstruction to the face of the door (Assuming a 6-9/16” jamb depth, 10” wall – 6-9/16” = 3-7/16”. Add this to the 3” to equal 6-7/16”.

    (d) add for clearance between the door and the face of the obstruction at 180° of swing (generally 1" or more). If, for instance, you have a 13⁄4" thick door: (an example would be if you also had 1” of baseboard trim to clear. (6-7/16” + 1” = 7-7/16”, round up to 8”)

    In this scenario you would need a 4” X 8” Wide Throw Hinge.

    Note: A butt hinge this wide may require a parallel bevel on the lock jamb if using a pair of doors.

  23. PatriciaCranberry | | #23

    I've read this Q/A string and wonder if I should post as a new question or just add to this..... But I think I may need a hand holding session. I'm preparing to order a inswing french door that will be installed in a rigid foam wall...not too thick..but thick enough I think I need some advice on jamb widths, etc before ordering. My wall is comprised of the following layers from in to out all in inches: 1/2 drywall. 5 1/2 stud, 1/2 OSB sheathing, 1 rigid foam (CZ3), 3/4 furring,__ exterior trim? (not sure). All my windows will be installed as outies and were ordered with flush frames so that a custom wood jamb will be added after installation. But what about this door? I'm intending it will be installed as an outie too....Will my door not open properly unless I tell manufacturer about my wall thickness?. and What distance do I give them? drywall to furring? (my windows are being installed on 3/4 furring frames that are the same plane as the vertical furring). Do I need to employ the 'narrowed" wall approach to the adjacent walls to allow the doors to open fully. By fully I would love 170ish degrees but could live with 90.

  24. dankolbert | | #24

    Have you asked about wider jambs yet? Should be available. Where are you putting the windows? At the sheathing, the insulation, or the strapping?

    You can also just get 6-91/6" jambs and attach to the sheathing. Then go with an exterior extension jamb and trim. Make flashing a little trickier but not too terribly. Consistency between doors and windows isn't as important as consistency among each, in my opinion.

  25. PatriciaCranberry | | #25

    I've worked and Google Sketchup-ed my way through this. Yes. I'm on the verge of ordering the widest jamb available (8 5/8). Windows will be at furring/frames layer. This door will need to be set in a bit requiring a trim carpenter to build some custom trim at the drywall frame junction. As proposed, the door handle should be the only thing that could hit the adjacent wall. :)

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