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Outie doors

AHTTAR | Posted in General Questions on

I’m installing 2″ of foam over wall sheathing and a 3/4″ rainscreen. Outie windows are very straightforward, but doors I’m still trying to wrap my head around. What do you use to support the threshold since the door will be 2+ inches overhanging the foundation? Also, what do you use to cover it up?


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  1. GBA Editor
    Martin Holladay | | #1

    The details will vary from job to job, depending on the relation of the foundation to the above-grade walls. In your case, where the rigid foam overhangs the foundation, the easiest solution is to install the door on a pressure-treated subsill (a 2x8 or 2x10). The illustration below does not really apply to your case, but gives you an idea of what I'm talking about.

    In situations with so much rigid foam that a 2x8 or 2x10 subsill provides insufficient support, the answer is probably to design a wider foundation or to install an innie door.

    For more information on installing exterior doors in thick walls, see Windows and Doors in Double-Stud Walls.


    1. The_Wagonista | | #16

      Hi Martin,

      I'm in a similar situation as I need to install outswing exterior doors with 2" outsulation (+ rain screen and siding). Unfortunately inswing is not an option in this instance as there will not always be clearance inside.

      I looked at that picture and am wondering how the subsill would be different from a jamb extension? Also, if I frame my walls with 2x4, but the RO with 2x6 or 2x8 would that give me enough support under the door and a decent place to screw in the jamb and still have a fully operational outie door?


      1. Expert Member
        Peter Engle | | #17

        The big difference between a door sill and a jamb extension is that the door sill has to support the weight of traffic. People, and especially furniture on mover's handcarts are pretty heavy. A 2x subsill can extend a couple of inches without trouble. More than that, and you either have to fasten blocking under the sill, or go with an innie door like Martin says. I've done sills as much as 4" out, with solid PT blocking fastened to the foundation under the sill. You could probably do more if you really want to, with solid blocking and/or steel angle. You just have to consider the heaviest weight that it will ever have to support.

  2. AHTTAR | | #2

    Thanks Martin. Problem is my slab is my finished floor so I can't add height with a subsill. I've started looking into the detail on an innie door. Is there anything special to think about when doing innie doors with outie windows as far as flashing details go? Technically the WRB is in a different place for both options. Thanks

  3. AHTTAR | | #3

    The only other thing I can think of to avoid mixing innies and outies would be to add a ledge on the outside of the foundation under the threshold. Could be PT 2x bolted flat with the 1.5" edge supporting the door. Then either do peel and stick or make a pan flashing. Other option is to chip away 1.5" of the foundation wall and add a subsill which would be the cleanest option but a total pain in the....

  4. rocket190 | | #4

    Is the floor already poured? Also, do you have frost walls?

    In my case, I had frost walls, so the wall height was dropped 7" at my door openings. When they poured my slab they tipped the form out at the door openings so the edge of the slab extends 1.5" past the foundation wall.

  5. AHTTAR | | #5

    Hey Rick,

    I do have frost walls but they are already poured. How you did it makes sense but its too late for me. Missed that detail unfortunately. So now I need to get that 1.5" somehow or do an innie door and outie windows. Just have to figure out if I can get the flashing details right with a mix of innies and outies.

  6. AHTTAR | | #6

    So does anybody have any suggestions on mixing outie windows with innie doors? I could put my house wrap against the sheathing and install all the doors. For the windows I could flash them to the foam which is Rmax Thermasheath 3. Rmax says no problem on using it as WRB. Any thoughts on this setup that I'm missing? Thanks

  7. GBA Editor
    Martin Holladay | | #7

    I think that your suggestion would work.

    One more thing to remember: If a door is protected by a roof, the flashing details at the top of the rough opening are much less critical than they are for an unprotected door. There are so many advantages to protecting every exterior door with some kind of roof that I would call the roof essential.

    So make sure your door has a roof, and don't worry too much about the flashing details at the top of the rough opening for the door.

  8. AHTTAR | | #8

    Wow, bold words Martin. I have 3' overhang/soffits over all doors and windows. I'm also doing separate 3' overhangs over each door to keep snow, etc clear. Between that and the "innie" I can't imagine too much water is getting in. Not to mention MT is a pretty dry climate.

    That said, I'm not totally sold on foam as a WRB because of shrinkage and tape failures. My siding is 606 steel panels so it does have to actually be waterproof since the seems wont be lapped.

    SOOOO....I'm still considering doing all innies including windows. Gotta decide today.

    Thanks Martin.

  9. AHTTAR | | #9

    Hey Martin, one more question if I could. If I were to do innie doors and outie windows as I said above, what would you suggest I do with the wrb around the window openings? They will be flashed to the doors like normal, but the windows will be flashed to the foam. Since the windows will have plywood boxes I either need to cut the wrb and put it between the studs and plywood box or somehow get the wrb to come out and around the plywood, but that seems like a long way. Thanks

  10. GBA Editor
    Martin Holladay | | #10

    Innie windows don't require plywood window bucks. Only outie windows require plywood window bucks. For more information, see ‘Innie’ Windows or ‘Outie’ Windows?

  11. AHTTAR | | #11

    I understand that but I'm doing outie windows and innie doors. Flashing doors to wrb and windows to foam.

  12. GBA Editor
    Martin Holladay | | #12

    Sorry -- I got confused.

    It sounds like you intend to use your rigid foam as your WRB. Is that correct? If so, your window flashing needs to be integrated with the WRB -- in this case, the exterior face of your rigid foam. For more information on this approach, see Using Rigid Foam As a Water-Resistive Barrier.

  13. AHTTAR | | #13

    I guess I'll just have to make a judgement call as I don't think I'm explaining correctly. My setup is OSB, WRB, 2" foam, 3/4" strapping. Since my slab is poured and I don't want to deal with extending the sill threshold I want to install my doors as innies and continue as planned installing my windows as outies. I was thinking to flash the doors to WRB which is why I'm putting it behind the foam. I would then flash my windows to the foam. Essentially I would have two separate WRB layers since the doors and windows would be flashed to separate places. Make sense?

    IF that makes sense, I was wondering what to do with my WRB (housewrap) on OSB behind foam when I get to window openings. Since the windows will be flashed to the foam layer, what would you do with the housewrap? Tuck it into window openings and build plywood boxes on top of it or build plywood boxes and then install housewrap and crease at box?

    Thanks Martin, sorry for the confusion.

  14. GBA Editor
    Martin Holladay | | #14

    Here's my advice: consider the rigid foam to be your WRB. Flash as described in my article on using rigid foam as a WRB. Do whatever you want with the housewrap behind the foam.

    At the door opening, you can either (a) depend on the roof overhang to keep everything dry, or (b) intergrate the door flashing with the housewrap.

  15. AHTTAR | | #15

    Sounds like a plan, thanks Martin.

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