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Window Bump Out Flashing

BuildingIn2020 | Posted in General Questions on

We’re in the middle of a build and about to install windows. My window supplier has a different method to install than my contractor. I can’t find either detail to completion anywhere else. Here’s the details:

2×6 wall
1/2″ plywood sheathing
Wrapshield IT for WRB
Strapping to build out the window for rainscreen

Here’s where opinons differ. 
Contractor wants to wrap furring strips with say 1′ strips of the WRB. 
Seal the nailing flange to WRB strip. 
Flashing Tape over the flange and strip

Window Supplier wants to caulk and seal flange directly to furring strip. 
Then flash tape the flange to the WRB on the sheathing. 

I can’t find any examples of either being done. This Tyvek Youtube video is the a hybrid of both and the closest example I can find.

What is the best way to go about this? If the furring strip is sandwiched between WRB would it act the same as caulking the furring strip to the WRB?

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  1. Expert Member

    Is there some reason for mounting the windows outboard of the furring strips, rather than on the sheathing as is usually done?

    1. BuildingIn2020 | | #2

      Only reason is to have the windows flush with siding.

      1. Expert Member
        MALCOLM TAYLOR | | #3

        Mounting the window on the sheathing can mean that If the furring and siding are too thick, you can end up with the edge of the siding not being covered by the part of the window frame that is outside the flange. I typically use 1/2" plywood strips so it isn't an issue.

        Here is a window with furring from a job several year ago. Since then I have tried to keep the furring off the flange, which allows better air movement and avoids the bulge used by the thickness of the flange underneath

      2. Expert Member
        MALCOLM TAYLOR | | #4

        The windows when finished on that project:

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