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Community and Q&A

Zip R Sheathing used for window buck

steve41 | Posted in General Questions on

I’ve done some searches, but didn’t find much info:  Has anyone used ripped Zip R sheathing for window bucks for “outie” windows?  I did find one FHB video, but it used a box-frame type window bucks made from Zip R, whereas I’m looking to face mount the Zip R.

In my application I would have 2″ polyiso over the exterior, and then ~3″ wide ripped lengths of 2″ thick Zip R around the rough openings.  Or would the detailing become to0 difficult and I should just stick with solid wood bucks?

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  1. Expert Member
    Michael Maines | | #1

    Steve, I have drawn that detail on a couple of occasions and I think it could be a good option to minimize thermal bridging, but so far the detail has ended up changing by the time we get to construction. Assuming you're going with flanged windows, the nails through the flanges would need to go back to the framing; usually at least 1 1/4" penetration into the framing is required. In your case that would mean nails at least 3 3/4" long, or more depending on sheathing thickness.

    Have you heard of Thermal Buck? It's made for this situation.

  2. steve41 | | #2

    Michael- Thanks for your reply. Originally I had planned to use Thermal Buck, and still may, but it looks like it would be 3-4x the cost of using ZIP R for the bucks. Also I decided to explore other options after reading this article:

    What caused you to move away from using ZIP R for the bucks? My only concern is the exposed polyiso sandwich layer on the interior of the framed opening, and related flashing complications. I do like the continuity of the plywood-box style option.

    1. Expert Member
      Michael Maines | | #3

      On one project we changed from continuous exterior insulation to a double-stud wall. On another we went with solid wood bucks for simplicity and because energy performance was not a top priority. On one other project I just remembered we were looking at ripped Zip-R and Thermalbuck, but ended up going with 6" of exterior insulation so neither of those approaches would work.

      I have had projects with innie, Euro-style windows where we used ripped Zip-R behind the extension jambs.

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