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Question on “Deep Set Brickmold Trim for Innie Windows”

rockies63 | Posted in General Questions on

Since I’m not a member I can’t ask questions about a Prime article (or read the entire article). Maybe this is addressed later on in the article but I don’t know.

The article states: “If you install flanged windows on the exterior side of a sheathed 2×4 or 2×6 wall, and you then install exterior rigid foam, you end up with an “innie” window.”

I’m guessing from this description that the window flange is installed right on top of the sheathing and/or WRB and then the rigid foam is butted up against the edge of the window? Shouldn’t there be a “picture frame” of 2x material around the window opening and if so then the window flange would be nailed to that (thus bringing the window farther out in the wall plane and resulting in less of an “innie” effect). The “picture frame” would also provide an edge for the rigid foam to butt up against. 

I looked at the link for Northerm Windows provided in the article but couldn’t find any information on their trim design or whether they recommend applying it over a “picture frame” or not. Does anyone have drawings or sections of this products trim details?

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  1. Expert Member


    You can sign up for a limited time trial and have access to the article.

  2. GBA Editor
    Martin Holladay | | #2

    The outermost layer of the wall assembly (before the siding is installed) will be the furring strips. You'll need furring strips around each window opening, of course -- both vertical furring strips and a couple of horizontal strips (one at the head and one at the sill). The main purpose of these furring strips is to facilitate installation of the siding.

  3. Expert Member
    Peter Engle | | #3


    If you sign up for the limited time trial, you can also research the differences between "innie" and "outie" wndows. There are a number of articles and construction details in the library.

  4. rockies63 | | #4

    Martin: If an exterior wall is built out of 2x6 framing lumber and covered with 5/8" sheathing, a WRB layer, then let's say 2" of rigid insulation, then 3/4" furring strips and then 3/4" siding the thickness of the wall outside of the sheathing layer would be 3 1/2".

    If the window flange is attached to the sheathing layer then the window trim should be at least 3 1/2 to 4" deep in order for the siding to butt up against it.

    The article seems to suggest that this is where the window flange is installed - on the surface of the sheathing, thus creating an innie window. But if you installed a wood picture frame around the window opening (either the same depth as the rigid insulation or perhaps deeper) the flange could be attached on top of that and the depth of the trim could be reduced. Would that still be an innie window?

    I wish the Northerm website had some detail drawings for this product showing its installation, either with a picture frame around the window opening or without.

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