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Window replacement

user-466364 | Posted in General Questions on

Hi…. I am helping a friend reconstruct an exterior wall, and will be replacing a window. The window purchased (and non-returnable) is a replacement window type.

Since we will be removing all the siding for the reconstruction, I assumed that a regular flanged was purchased.

I understand the concept of installing the window by leaving the siding and window framing in place, but cannot find any instructions on how to use this window in what is essentially a new construction application. The biggest “head-scratcher” is how to finish the window framing, and wondering if this framing should be installed first then the window…

Any help and visuals would be greatly appreciated. Thanks.

Rob

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Replies

  1. user-466364 | | #1

    I did not mean to say window framing, but exterior window trim!

  2. GBA Editor
    Martin Holladay | | #2

    Rob,
    I'm beginning to feel old. I remember the era of rotary dial telephones and windows without flanges.

    The window will be fastened to the rough jambs with masonry clips or with trim screws installed through the window jambs.

    The exterior of the window frame is usually installed in the same plane as the exterior of the wall sheathing (unless the wall has a rainscreen gap). The exterior window trim (casing) fastens to the window framing (usually with a 1/4 inch reveal) and spans the gap around the window; it is also fastened to the sheathing.

    The exterior trim (casing) can be attached to the window before it is installed, or it can be attached after the window is installed -- your choice.

    .

  3. davidmeiland | | #3

    You can usually install your own metal flanges if you want to. Go buy some 1-1/2" x 1-1/2" or 2" x 2" metal flashing, get a pair of snips and some panhead screws, and make flanges for all four sides of the jamb. One leg of the flashing goes against the jamb, pointing toward the inside of the house, the other leg is your flange. Snip the jamb legs as needed so they stop at the corners. If you really want to go all-out, prime the jamb first and use sealant to bed the metal as you screw it on.

  4. user-466364 | | #4

    we will be creating a rainscreen.... so it should be flush with????

    In the photo provided I do not see a casing. This window essentially floats inside the frame. So trying to figure out the trim detail including the gap between the window and the frame. With flanges you would finish trim over them, and bring the siding up against it.... this where I am lost. Is it essentially the same concept? Which also brings up the question of waterproofing/flashing around the window?

  5. GBA Editor
    Martin Holladay | | #5

    Rob,
    Lots of questions -- I hope that someone on the job site does some research before the installation begins.

    You need to flash the rough opening, not the window. GBA has an 8-episode series of videos that you should probably watch. Here is the link to Video #1 in the series: Window Sills That Won't Rot.

  6. GBA Editor
    Martin Holladay | | #6

    Rob,
    There are many ways to install a window when your wall includes a rainscreen. Windows can be installed as "innies" or "outies." Innie windows often have no exterior casing. Even if you prefer an outie window, exterior casing is optional.

    Here is a link to an article with more information on rainscreens: All About Rainscreens.

    I will post some images below to give you some idea of your options when installing a window in a wall with a rainscreen gap.

    .

  7. user-466364 | | #7

    Hi Martin,
    Martin.... I wasn't using correct terminology.... my mistake. I do know how to flash the rough opening... I've done several hundred of them over the years, but have never installed anything other than a new build window with nailing flanges and know how to do the exterior trim on those. This replacement window just has me wondering if the finish trim is the same or if there is anything special I should do given that there is no nailing flange that spans the the space between the window framing and the window. I want to make sure that it is water tight.

  8. GBA Editor
    Martin Holladay | | #8

    Rob,
    1. Of course you need to install the window in a watertight manner. The usual way you do this with a flangeless window is to make sure that the rough opening is properly flashed. The flashing has to be integrated with the WRB.

    2. Flangeless windows can be installed as innies or outies. It's your choice.

    3. You wrote, "This replacement window just has me wondering if the finish trim is the same." You get to decide how to trim the window. You can install traditional exterior casing or no casing -- it's your choice. Look around at the windows in homes in your neighborhood to get a sense of all of the different ways that designers decide to trim windows.

    If you decide to install exterior head casing, you'll need to install metal Z-flashing above the head casing. The WRB usually laps over the Z-flashing.

  9. Expert Member
    MALCOLM TAYLOR | | #9

    Rob,
    If you are uncomfortable with the details and more familiar with flanged windows, probably the easiest solution is to just make a flange out of aluminum or vinyl L sections. Screwed it into the frame and bedded in sealant you can now install it as you usually do.

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