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Community and Q&A

Innie Window Install in ICF Wall – Zone 4B

Peter L | Posted in Green Building Techniques on

I am trying to find a good detail on how to install an “innie” window in an ICF wall with a stucco exterior finish? The windows are European T&T and fixed. The wall assembly is 2.5″ EPS x 6″ concrete x 2.5″ EPS. Most of the details out there are for “outie” installs and most are for wood framed walls and siding finish. Appreciate any help…

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  1. Jin Kazama | | #1

    Are you at design stage or is this for an existing wall ??
    How were the window opening planned? using wood bucks ?

    There is no magic here for innie windows on icf.
    Look at european windows installation on block walls on youtube .

    Exterior finish ?

  2. GBA Editor
    Martin Holladay | | #2

    Peter L,
    The challenge is to choose materials that are waterproof. The rough opening needs an exterior sill that is as waterproof as a roof. Among your choices for the sill material are rot-resistant wood like cedar, solid-surface material, or metal flashing (preferably copper). Then you have to choose durable materials for your exterior jamb extensions.

    These details are possible, but the work is more challenging and expensive than outie windows. You need to think like a roofer and you need to do an impeccable job with your flashing details.

    Start with an oversized plywood buck with a sloping bottom, and use plenty of peel-and-stick. Choose durable materials, and make sure that the water than runs down your exterior window jambs is picked up at the lower corners and directed outside by durable flashing.

  3. Peter L | | #3


    Thank you for the response. I was also considering using window bucks that are "wood free" since they now make bucks that are 100% ICF/EPS blocks. Fox Buck is one such buck that creates a window or door area without wood. It has solid attachment points within the buck area, which then are anchored into concrete. Would something like this help with the innie window install, since there are no materials that can rot when exposed to weather?

    Other than that, I have to go the route of treated wood bucks. Do you have any details showing a good ICF innie window install?

  4. Peter L | | #4


    To answer your questions:

    1-This is in the design stage.
    2- No decisions made on whether we will use wood bucks or other ICF bucks, still undecided
    3- Exterior finish will be synthetic stucco

  5. GBA Editor
    Martin Holladay | | #5

    Most ICF manufacturers provide details for window installation. The first step is to contact the manufacturer and ask for their detail. If the manufacturer recommends that all windows must be installed as outies, then you will be on your own, and you'll have to accept the risk of any future problems.

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