Double hung windows water leak

Old 12-21-18, 11:02 AM
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Location: Mass.
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Double hung windows water leak

Looking for some input regarding my leaking windows.

I have a number of windows in my house that are leaking water into the walls. I cannot find the source of the leaks. These are double hung, wood framed, about 35 years old (original to the house). The exterior of the house is clapboard on plywood. The water seems to be at the bottom of the window. I suspect the water is getting into the sill (traditional slanted wood sill). The sills are not rotted or punky. The sill is constructed with a nosing about 1Ē square that extends out. From the inside, I can see water at the seam between the nosing and the base of the sill (Iíve removed the inside trim and opened the wall to see under the window). That seam is positioned over the inside of the wall, thus water is seeping into the wall cavity.

Iíve sealed the exterior sills with caulk and paint. Even tried ďFlex SealĒ. Iíve sealed around the edges where it meets the siding, and on the bottom. Iíve sealed the sides of the trim and the tops. Flashing at the top of the window are good. Still no luck stopping the water.

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Old 12-21-18, 05:25 PM
Join Date: Oct 2015
Location: Ct.,USA
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It appears the sill is only as wide as the window and attaches to the vertical frame on each side of the window. If not sealed, water on top of the sill can leak at these joints, down the vertical to the area under the sill where you can see it. It appears the sill extends beyond the clapboard so water wicking up the sill bottom from the outside shouldn't be a problem.

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