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Community and Q&A

Installing windows to be replaceable without compromising the WRB

mackstann | Posted in Green Building Techniques on

I’m (very slowly) planning to retrofit a few inches of foam onto my house, with a rainscreen and new fiber cement siding. I don’t think new windows are justified from an energy point of view, nor do I particularly want to spend the money on them. But they’re vinyl and I really don’t think they’re going to last as long as the siding, so I’m going to re-install them with proper flashing with the intent of making it possible to replace them in the future without too much pain.

How should I do this? Using the typical self-adhered flashing products (I’m leaning towards DuPont FlexWrap and StraightFlash to tie in with the Tyvek) means that several inches need to be accessible around the window. So that means I need maybe 1×4 trim around the window, which I’m okay with. I will also need to cut away the foam around the window to get access, which is fine — I can just re-attach the cut off pieces afterwards. I think there will also need to be rainscreen boards underneath that will need to come out and put back in. Will I try to tear off the flashing? Will it even come off? Do I just stick new flashing over it? Or do I somehow cut it off and add new Tyvek/flashing around the whole window opening? I’m not sure even 1×4 trim would leave enough room to do that well. 1×6 might look excessive on my small house.

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  1. GBA Editor
    Martin Holladay | | #1

    You're asking the right questions. It's hard to come up with prescriptions that suit all cases, however. Here are some principles:

    1. Flangeless windows will be easier to replace than windows with flanges. (Most manufacturers will sell their windows with or without flanges.)

    2. When you are installing the windows, your mantra should be, "Flash the rough opening, not the window." If the rough opening is properly flashed, then the window will not be part of the flashing system, making it easier to replace the window.

    3. Stainless-steel screws are easier to remove than nails or fasteners made of ordinary steel.

    4. Your Sawzall is your friend.

  2. jackofalltrades777 | | #2

    Best practice as Martin already stated is to use FLANGELESS windows and stainless or coated SCREWS are your best friend. A quality window should last 25+ years before it might need replacing. Overhangs are your friend since they protect the window. Cookie-cutter builders usually slam nails and use flanges because it's fast and cheap. A custom home should use flangeless and screws.

  3. KeithH | | #3

    DIY Experience here to share:

    I have replaced windows on my rental. Cardboard siding straight up to nailed on flanges, no exterior insulation sheathing. My recipe was: circ or trim saw off ~2" of siding (plunge saw is nice for directly below the soffit); remove window; flashing tape; install new window with screw on flange; flashing tape over window; scribe trim line using 1x4 cedar board; circ/trim saw again the scribed line; install cedar boards over flange with screws. With that recipe, I can pull the cedar boards, though not easily as I'm sure the screw heads will get painted on over the years. I suspect the windows will outlast the cedar so I'm not too concerned about the screw on flanges. I'd call this retrofit easy/normal.

    However, my own house has an exterior foam buildup thick enough that I can't use the flange. For one window only, I went without a screw on flange. Since I had to hack the heck out of the stucco (and underlying layers) to get the original nail on flanges off, the 'block' frame window didn't really buy me much in terms of preserving the siding. Using the block frames might help the next installer replaces the windows. I'm doing innie windows without 'buck frames' (perhaps the wrong term?).

    I ruled out making bucks to extend the windows out to the stucco exterior surface; I don't like the look.

    However, the thing about your approach that would worry me is that you are doing the siding without doing the windows. If your experience is anything like mine, you need to be prepared to do the windows if you do the siding. Perhaps you should attack one surface at a time doing windows, outsulation, wrb/etc, interior re-trim etc. Then when you are done with one side of the building, you won't have to revisit the exterior for 25 years.

    What I would really like to find would be a trimming system that helps deal with the thick exterior insulation problem. I'm going to try casting some custom concrete trim pieces that I will attach with structural screws) but I haven't done it yet and expect it to be challenging and time consuming.

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