Sealing a basement window


Old 04-05-08, 12:05 PM
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Sealing a basement window

I've got an old house that a previous owner built a large dect out the back door. They tried to seal up a basement window that's now under the deck, but it leaks water down the interior wall when it rains hard. How do I seal it up properly?
The basement is unfinished (cement walls with studs in place) and I want to make it into my "Man Room". Can't start until I fix the water problem.

Thank for your help,
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Old 04-05-08, 12:23 PM
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You could attempt to caulk from the inside, but since the leakage is occuring on the outside of the window your best bet is to start there. Not sure how convenient it is to crawl under the deck, but I would guess that's what is going to have to happen, unless removing a few floor boards right there would be easier.

I'm guessing it might be poor glazing around the glass... or maybe it's coming in around the frame. A thrid possibility is water getting into the framing ABOVE the window, such as where the deck ledger attaches, which could then leak in above the window... not necessarily around it.

So I'd recommend you be prepared to get under the deck, be prepared to scrape old glazing putty and reglaze the glass... be prepared to scrape old paint and recaulk the exterior of the frame, or maybe caulk the sash shut too while you're at it to ensure everything is sealed. While under there, you'd want to inspect the top of the rough opening (usually this is the sill plate of the house, which rests on the foundation) and see if there is any evidence of water damage, which would indicate water infiltration from above the window. Good luck, and I don't envy you crawling on your belly under there. Hopefully someone can hand you the tools you'll need.

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