Leaking window

Old 03-10-17, 02:21 PM
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Leaking window

I'm not sure I'm in the right forum, but thought it was close enough.

We have a newer house, built in 2010. The downstairs bathroom has a small double pane window with tilt sashes. The house is vinyl siding. A few days ago, we had a violent storm with really strong driving winds and rain. For about an hour, rain water was leaking inside the window from the top right corner from above the frame. Never seen anything like it.

The next day, i went outside, expecting loose or missing siding, but everything was solid. There are no gaps in the siding around the top or sides of the window frame. The outside window molding is at least an inch above the siding, and I would expect there is some flushing under the siding to push water away.

Can someone walk me through troubleshooting or potential repairs to prevent recurrence? Again, this has never happened before. Thank you!
Old 03-10-17, 02:36 PM
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Vinyl siding is not waterproof. What commonly happens is that wind blown rain gets driven behind the siding, (which is fine as long as you have housewrap behind the siding).

Problem is that a lot of windows are not flashed properly, so when that water gets to a window, it runs right in. To correct this you will simply need to unzip a piece or two of vinyl siding over the top of the window. (Use a Malco sideswiper unlock tool. You can probably find a video on youtube.)

Once the siding and top j-channel is off, you can flash the top of the window. If it has a nail fin, you will want to cut a flap in the housewrap and fold it up and out of the way. Then use a window flashing tape like Pella tape, and tape the fin to the sheathing. Then fold the housewrap back down, tape the ends of your flap, and put the siding back on.

If the window has trim (instead of nail fin) you should install a z-flashing drip cap over the trim... and then tape it just like the fin mentioned above.

The water is probably running behind the siding at the bottom corners of a window directly above the one that leaked. If you want more info on how to correct that, you can post a picture of your house and ask for more instructions.

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