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Window Head Flashing on a Buck with Rockwool CI

spraggins | Posted in Energy Efficiency and Durability on

We are trying to figure out how to handle the waterproofing details on a flangeless window that will be set in a plywood window buck on a house that has Rockwool continuous insulation with furring straps. Specifically we are not finding consensus on the head flashing with what few examples are in the wild. The Comfortbatt 80 installation guide gives two very different views depending on whether the window has a flange. Their flangeless one leaves us head-scratching on how we would work in and support the extensive drip cap this historic trim package calls for. We have sketched an idea up, but welcome some expert opinions to weigh in, especially on how to handle the ledge the top of the buck makes.

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1

    spraggins,

    It is a tricky detail.

    My preference would be to take the metal head-flashing back behind the rockwool to the WRB. That takes any load off the buck itself and avoids the possibility of moisture
    pooling between the buck and the trim.

    Whether you do that or use the detail you have drawn, I don't think the Cor-a-Vent adds anything, and I would replace it with a piece of horizontal furring.

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