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What's a good way to detail an exterior corner with rigid foam?

I'm planning on improving an existing 2x4 wall by installing 2 layers of 2" polyiso or 4-1/2" nail-base panels. I've found good pointers on this site for most of the details, but am still unsure about how to handle the exterior corners so that the rain-screen strips and siding corner-boards have something solid to attach to. The corner-boards will likely only be a few inches wide, so not wide enough to catch any framing. I'm assuming a butt-corner with nail-base, so there would be OSB on only one side of the corner. How do you do this without creating a thermal bridge?

Hope that makes sense.

Any suggestions?


Asked by Andrew Thompson Zone 3a
Posted Dec 12, 2012 2:35 PM ET


2 Answers

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One technique we've used is to trim screw the edges of 2 sections of Advantech together to form a furring "corner board" (or other weather durable sheet good wide enough to reach from corner back far enough for a structural screw to be able to attach firmly to a corner stud).

Your trim boards and siding won't be thoroughly back vented at the corner, but you'll have good firm nailing attachment and still keep a clear foam corner without a thermal bridge.

Answered by Jesse Thompson
Posted Dec 12, 2012 8:05 PM ET


Thanks for the response Jesse. I was thinking of something similar. I'm not sure that the lack of lack of venting near the corner is that big of a deal, but I'm always curious about best practices.


Answered by Andrew Thompson Zone 3a
Posted Dec 15, 2012 12:01 PM ET

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