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My bathroom fan leaks water during very heavy rains. It is on the first floor. The exhaust is also on the first floor on the side of the building, not the roof.

The fan is on the ceiling and there are no leaks during light rains.

What could be causing this? Any ideas on how to go about fixing this?

Thanks for your time! :)

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  • Have you pulled the cover to determine whether the fan itself is the water conduit or if the leak just happens to show itself in the ceiling cutout?
    – isherwood
    Commented Jun 15, 2017 at 21:38
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    The external exhaust vent should have a flap or louvers that open to let air out but block stuff from blowing in. Make sure they aren't damaged or stuck open by debris. That said, it isn't hermetically sealed. So torrential rain and heavy wind could blow some amount of rain into the duct. But as isherwood suggests, if it isn't the vent, inspect where the water is coming from when it happens. You will need to remove the cover, and maybe drop the fan, to see the inside of the housing. See if the water is coming from the duct and not some other leak dripping into or around the housing.
    – fixer1234
    Commented Jun 15, 2017 at 21:46
  • Thanks for that guys! fixer1234: Rain being blown into the exhaust vent is what I'm thinking. It only happens during torrential down pours....And usually it's really windy at the same time. So can this be fixed? The vent is high and I can't reach it with a standard ladder. What professional should I consult? A handy man? Roofer? Sider? Thanks :)
    – DIY Newbie
    Commented Jun 16, 2017 at 3:11
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    @DIYNewbie - You would for want to select a professional that had the necessary ladders and can show that he is properly insured during the course of your job. Besides the categories of professionals that you suggested, any one of which may be possible, you could consider a house painter that is not currently busy painting,
    – Michael Karas ♦
    Commented Jun 16, 2017 at 3:31
  • What's required to fix it depends on what the problem is. It could be as simple as pulling some debris out of the vent or caulking, or more complicated. The first steps would be looking at the vent up close and looking inside the bathroom fan housing during a rain to see where the water is actually coming from.
    – fixer1234
    Commented Jun 16, 2017 at 17:14

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I would suspect your flashing around the wall cap on the outside wall. Seal it with caulking and then see if it leaks next hard rain. There has to be a breach of some sort at the wall cap as that is the only portion of your system exposed to the elements.

When it does leak, is it just a hard rain, or one accompanied with high winds too? Could be the wind is forcing the rain into the wall cap

If it still leaks after caulking and you dont think high wind is a culprit, you could try replacing the the wall cap.

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  • Jeff: Yes, it occurs during high winds accompanied with hard rain. Thanks so much for the advice! I really appreciate it.
    – DIY Newbie
    Commented Jun 19, 2017 at 15:08

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