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Fastening window trim around innie windows

Salesi | Posted in General Questions on

How do you fasten prefabricated trim around an innie window? If I prefabricate a window trim out of vinyl or fiber cement with a 1 x 3 extension and 1×4 trim piece that lays flat on the exterior wall and fit it around the window, how should the trim be nailed or screwed to the wall without compromising the WRB? Should I apply the exterior insulation and rain screen first and them screw or nail the trim to the rain screen? I can hold the insulation back from the window 3/4″ to fit the extension jamb against the sheathing and caulk it to the window. Thanks for anyone’s help.

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  1. natesc | | #1

    I have used galvanized right angle brackets to attach a preassembled jamb extension. You need to make sure your screws clear the window flange which is why something like pocket screws doesn't work.

    The window trim can be attached to the furring strips.

    I am not a fan of caulk because it will fail within a few years and make things wetter than without, but that's just me. I think a lot of people disagree with me on that.

    I am also careful to install everything so that the window can easily be replaced in the future by just removing the trim, jamb extensions, and small strips of foam.

  2. Expert Member
    Michael Maines | | #2

    Salesi, it depends on your wall assembly and window buck assembly. I try to keep fastening in mind when designing thick walls. A few of my tricks are here: Nothing too unusual, but builders often ask about this.

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