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Old stucco house with no WRB on exterior

Mill_house | Posted in General Questions on

Hello,
Climate zone 7 Canadian Prairies
My original 1 1/2 story stucco house (built 1940s) does not appear to have any felt under the stucco (from what I can see). It does have a rain gap though. My neighbours did an extensive remodel on their house, including the exterior, and they said their house did not have felt. I am not planning on doing any work to the exterior of my house.
My question is now that I am gutting the inside – going room by room, adding roxul insulation to the 2×4 walls, then Smart vapor, then drywall – do I need to do anything with each stud bay prior to adding the insulation in order to account for the lack of  WRB/felt on the exterior?   On the off chance that there is felt somewhere on the exterior, I hope whatever you recommend for the interior works for that situation too.
Thanks for your help.

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Replies

  1. Peter Yost | | #1

    Hi Mill_house (be great to have a real name for our GBA Q&A community...) -

    Your home should tell the story about what you need in terms of making up for the apparent lack of both a WRB AND a bond break between the stucco and the rest of the wall (although you DO have a "rain gap?" -- having a hard time reconciling that description; you might need a sketch to clarify). In other words, if your structural sheathing and framing show no signs of degradation, water staining, high moisture content, I guess you lucked out--with design (big overhangs) or your climate (cold but very dry...).

    You do need to be careful though: adding insulation decreases the energy your exterior wall will see, and if it was that energy loss that was drying out your assembly, and you are reducing that energy, you could take a wall that worked to one that does not work, at least as well.

    I would focus on how your window sills have done over time, given they represent the bottom of your largest penetrations. Are they in good shape, no signs of moisture damage or water-staining?

  2. Mill_house | | #2

    Hi Peter,
    I've attached a photo of the corner of the house.
    The sheathing has an occasional staining mark. I have no way of knowing how old the marks are though. The house is a cape cod style house that only recently received overhangs.
    Wondering how I can do what's right for the house (from the inside) given its apparent lack of felt on the exterior?
    Second question I have is regarding airtight drywall. Is it possible to install drywall this way when the wall assembly has a layer of smart vapor? Any videos I've seen always show airtight drywall being installed directly to wood studs.

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