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Constructing window bucks

John P. | Posted in Green Building Techniques on

I’m getting ready to cut the pieces for some window bucks. I’ve read this article: https://www.greenbuildingadvisor.com/node/42336 but it doesn’t specify how to attach the 3/4″ plywood pieces to one another – I’m going to use a waterproof glue, but should I use screws or a 2″ 18 gauge brad nail?

My walls are going to be 4″ of XPS, and I will be making an 8″ wide window flange for the flanged window units to attach to.

Additionally – it mentions for windows wider than 3′, a 2×4 should be placed below the sill for support. Should this be located at the inside or outside of the box? Or do I have to frame a bottom support the same depth as the foam?

Thanks!

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    John,
    Q. "It doesn't specify how to attach the 3/4" plywood pieces to one another - I'm going to use a waterproof glue, but should I use screws or a 2" 18 gauge brad nail?"

    A. As long as you don't split the plywood (with some fasteners, you may need to pre-drill), you can use screws or nails. Ring-shank nails are probably best -- ideally, stainless-steel ring-shank siding nails.

    Q. "It mentions for windows wider than 3', a 2x4 should be placed below the sill for support. Should this be located at the inside or outside of the box?"

    A. On the outside of the box. It is a horizontal 2x4, installed flat to the sheathing, directly under the buck.

  2. John P. | | #2

    Ok - I'll use stainless steel screws then - GRK makes a self-cutting tip and head I've had good luck with.

    As for the 2x4 - since I'll be making 8" wide window flanges, I'll simply use a 2x10 (I have enough scrap left over for two 4' windows) and rip it to 8" to match -> I'll mount it flush with the face of the strapping and inset it into the foam - I'll need to remove 1/4" x 4' of foam, but this shouldn't pose a problem.

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