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Community and Q&A

Window and sliding door leakage

user-6651407 | Posted in General Questions on

Climate Zone 5. Zip Sheathing. Exterior Siding not yet up. Open Cell Insulation in the walls.

We had tremendous amount of rain over the past two weeks. At the house tonight, I noticed the two basement windows, which are above ground, had leaked water each in the bottom left corner. These windows face the northwest. The window further to the left actually leaked so much, the insulation below is wet.

The two siding glass doors, one in the basement, oe directly above on the first floor, both leaked water. These door face the North East. We don’t have the retaining wall up outside the basement door, so I’m sure it came in from the mudslide that resulted from our two weeks worth of rain. The first floor sliding door, the leakage was on top of the door.

My husband is removing the wet insulation, and drying out the framing wood. He’s checking all the flashings tomorrow when it’s light again.

What other things should I add to check? I’m now concerned about all the Zip tape used throughout the exterior structure. It is overlapped, smooth, not wrinkled.

While I’m glad we caught this, I am also. Wet concerned.

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  1. GBA Editor
    Martin Holladay | | #1

    Your windows could have leaks between the sash and the window frame (that's a manufacturing defect), or they could have leaks between the frame and the rough opening (in which case the wet insulation is a sign of a flashing error by installers).

    Even if the windows are leaking between the sash and the frame, good flashing in your rough openings should have prevented your insulation from getting wet.

    So the first question is: Did your installers provide all of the flashing that the rough openings needed before the windows were installed? Ideally, each rough opening needed a waterproof sill pan. This sill pan must either be sloped to the exterior, or it must include a back dam.

    Once the sill pan is installed, the rough jambs must be flashed to direct leaks to the sill pan.

    Finally, after the window is installed, installers need to provide head flashing and more jamb flashing.

    Were these steps taken?

    -- Martin Holladay

  2. user-6651407 | | #2

    I am not sure. When looking at them, I couldn't find the defect. My husband is going out today to see if he can't fix it. Is there an inspector is a professional who can double check and find any more leaks? This is something I want to make sure is right. Simply not sure who to contact, if any.

  3. GBA Editor
    Martin Holladay | | #3

    You might start by talking to the window installers, and asking them to describe their sill pan flashing.

    If you need to do some diagnostic testing, you can learn a lot by masking certain areas with polyethylene and tape, and then spraying the test area with a garden hose.

    -- Martin Holladay

  4. user-2310254 | | #4


    This issue needs to be corrected by your builder and/or window installer. That said, it is helpful if you know what constitutes best practice for a typical installation. Check out this video by Matt Risinger for details:

  5. Anon3 | | #5

    That Matt Risinger video is actually incorrect... you need to put the window on before the Tyvek, not after it.

  6. Expert Member
  7. user-2310254 | | #7

    I think there is some variation in the sequencing for these strategies.

  8. Anon3 | | #8

    By putting window after house wrap, if water get's behind it, you'll get the problem OP is having.

  9. user-6651407 | | #9

    Our sheathing is ZIP, which has the WRB already attached. I think we found the issue with the windows. They had taped the bottom of the window after finishing all the rest of the flashing, which after watching the video that is NOT ok. We removed that bottom tape, and water drained out. We checked all the windows and are fixing the issue. We also have an inspector coming out today with his infra red camera to see if there is any water we missed. We still aren't 100% sure where the water came in at on the sliding glass door. We think it came in at the top, but hoping the inspector has some insight.

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