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Community and Q&A

Has anyone used liquid flashing for window rough openings and still spray foamed and taped the jambs and head of windows?

Jonathon S | Posted in Green Building Techniques on

We are installing European flangeless windows and have used zip liquid flashing for the rough openings. We’re planning to use air dam sealant on the interior. The window manufacturer wants us to use air dam on the exterior as well with and air gap between the two beads. Our ZIP Rep has said that the zip tape can be used to tape to the liquid flashing, and it seems less expensive and easier to use for our exterior. But the window manufacturer doesn’t like to mix tapes with liquid flashing. Has anyone used liquid flashing and caulk on interior but tapes on exterior? We would really like to just spray foam the cavity of the jambs and heads, and then use zip tape back to the sheathing…. but that’s not recommended by the window manufacturer.

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  1. GBA Editor
    Martin Holladay | | #1

    The liquid flashing that you installed in the window rough openings, if properly installed, will handle any water that gets past your flashing and your trim. The Prosoco AirDam caulk is your interior air barrier. So you're really all set. You don't need any more of a barrier on the exterior. In fact, it's a good idea if liquid water that ends up on the rough sill can drain to the exterior.

    To improve the R-value of the gap between the window frame and the window rough opening, you can use canned spray foam if you want.

    In most cases, any gaps between your window frame and the window rough opening are covered on the exterior by window trim. That's enough. Install Z-flashing at the head, and you're done.

  2. Jonathon S | | #2

    Thanks Martin for the response!!

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