Re: (metal) flashing a flanged window set in 3″ of foam…trying to get this right!
Zone 7 Kenora NW Ontario Canada
I am ready to get to work on my first wall(of my reno) , it is stripped to the plywood and the existing windows are ready to come out (they are 30 yr old tri-pane clear glass monsters, each 42w x 60h. they are being replaced with vinyl 24w x 30h tripane low e argon GeldWen windows.
My plan is to reframe for the new windows and install an RO extension (on the exterior of the plywood) for the window flange to sit on, since I’m using 3 inches of XPS foam I plan on ripping a 2×4 to 3″ in width (from 3 3/8″) and nailing it on edge to the exterior of the RO.
The extension would be treated as a Dudley box and be flashed with peel and stick as described in several articles here. My question is..
Q- How and where to apply metal flashing that goes over the top of the window? Does the flashing attach to the sheathing, the Tyvek that’s next to the sheathing or the foam?
Thanks
Tim
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Replies
Hi Tim,
The answer depends on there your WRB is located. It sounds like you are putting the Tyvek against the sheathing under the foam, so you need to take the flashing back to that p0int - which makes for some pretty deep flashing.
There are a couple of alternatives. You can move the Tyvek to the outside of the foam, or you can detail the foam as your WRB. Both those allow you to use standard head-flashing. If moving the Tyvek you would lap the flashing. If using the foam the flashing would get taped to it.
Thanks malcolm,
I like both of your suggestions...in particular using the tyvek on the exterior of the foam...is there an article with details on that method...thanks
Tim,
You detail the exterior house wrap the same as when installing over bare plywood, check Tyvek for details.
The only issue I've had is foam doesn't hold staples, what I've done is tape it at the top to hold it and a bit of spray adhesive to keep it in place until the rain screen strapping goes on. If you can source some long cap nails, those will also work but hard to find.
Hi Tim:
Here's a drawing that shows how that flashing should be lapped under the WRB. In your foam sheathed wall, as Malcolm said, executing this detail will depend on where you choose to locate your WRB. This article may be helpful as you think about that: http://www.greenbuildingadvisor.com/article/how-to-install-rigid-foam-sheathing