When I first started planning the water and air control details for this project, I knew the windows were going to be one of the tougher parts. Window framing for a typical post-and-frame building consists of a simple 2x wood frame extending horizontally between two posts, which, in the case of this structure, are 6 ft. on center, with two vertical boards fastened between the upper and lower horizontal frames (like in the illustration below).
Once the basic frame is constructed inside the wall cavity, horizontal wall girts are placed over the framing, a kind of window buck, if you will. My original thought was to have the buck placed around the window rough opening, flash the buck so I could extend the window flashing back to the water-resistive barrier (WRB), then add the wall girts for fastening the cladding.
In my mind, this wouldn’t be a difficult assembly to build; the framing crew didn’t agree. They insisted on not changing their usual assembly (having the exterior wall girts installed first). This meant I had to figure out how to extend the window flashing to the WRB.
There are two different window sizes for this project. The first is a roughly 3-ft.-wide by 3-ft. 6-in.-tall triple-pane casement window. The second is a 5-ft.-wide by 2-ft.-tall fixed-glass triple-pane.
Working through the details
We are using Siga’s Mavjest 200 and the manufacturer’s tapes on this project, so I referenced their “Ultimate Guide to Window Flashing” to help detail the rough openings. Unfortunately, there were no details showing how to flash a window when a wall has horizontal girts. However, there are details for how to flash a window buck, so that’s what I used.
My window detail includes…
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