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Proper flashing placement?

ddubx6 | Posted in General Questions on

My foundation sticks out past a wood framed wall, osb with taped seams, housewrap taped seams, 4″ of polyfoam, lower 12″ of wall has self stick membrane that completely covers foundation. I am getting ready to put up strapping and wood siding but noticed there is no flashing at bottom of wall. do I have to remove the foam and flash the entire wall to edge of foundation or can I put the flashing between foam and strapping, using sealer and tape on the foam to flashing edge .the distance from wall to edge of foundation is approx. 8″, so even with foam and siding I still have approx. 2″ to cover.

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  1. GBA Editor
    Martin Holladay | | #1

    Your description is unclear. I think we need you to post a sketch.

    If you want to try to clarify, here are some hints:

    We don't know what type of foundation you are talking about. Is it a slab on grade? A poured concrete basement wall? Something else?

    Your use of the word "wall" is confusing. It's better to say "above-grade wall" or "stud" or "bottom plate" or "wall sheathing" so we know what you are talking about.

    What crack are you trying to flash? Is it the crack between your wood framing and a concrete foundation? Or is it some other crack?

  2. ddubx6 | | #2

    sorry for the confusion, the foundation is a stone basement that has about 2ft above grade, it was reinforced at some time with approx 6" of poured concrete on the outside of it. the house walls sit on the existing stone part and the concrete part is wider than the house. it is this top of the concrete that i want to cover for looks and to keep water from collecting on top of it. the 4" of foam on the house walls cover some of the concrete so my question is can i just use flashing from the foam or do i have to remove the foam and start from the sheathing. there is currently a layer of self stick roofing ice shield that covers the lower 12" of sheathing and top of concrete but it is exposed and does not look good.

  3. GBA Editor
    Martin Holladay | | #3

    OK -- I think that I understand the situation now.

    The first thing to mention is that it's always important to know which layer of your wall is the water-resistant barrier (WRB), which is a code-required layer. (For more information on WRBs, see All About Water-Resistive Barriers.)

    I'm guessing that the WRB on your wall is the layer of housewrap between the OSB and the rigid foam -- a layer which you mentioned in your original question, but which is not shown on your sketch.

    Wall flashing (including window flashing, door flashing, and the type of flashing under discussion in this question) should always be integrated with the WRB. If lapping is possible, then the flashing should be properly lapped to the WRB, with upper layers lapping over lower layers.

    In this assembly, it looks like the peel-and-stick roofing membrane is acting as the actual flashing. I don't know whether your housewrap laps over the top of the vertical leg of the peel-and-stick -- but it should.

    Assuming that the peel-and-stick is installed properly, so that it can act as a flashing that is integrated with the WRB, then the flashing that you propose to install -- which I am assuming will be metal flashing that is bent on a brake, although you didn't describe it -- is mostly just a protective element to keep UV light off of the peel-and-stick, and to protect the flashing underneath from physical abuse. If that's the case, then the metal flashing can be installed as you propose, with its vertical leg behind the furring strips.

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