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Our bathroom exhaust vent was dripping after rain; I saw the tar on the vent cap was all weathered and worn away, so I cleaned it off and put fresh tar there.

It was fine through the rains in the spring but then we had a real hot Texas summer and no rain and last week we had our first heavy rain and the bathroom exhaust fan is dripping again.

I went up on the roof and don't see any holes or cracks.

How can I keep it from leaking?

Pic 1:

vent cap

Pic 2:

vent cap from above

Pic 3:

vent cap from the side

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  • Is it possible to access the attic and visually inspect to learn where the water enters?
    – Greg Hill
    Sep 21 at 13:08
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    Well, based on the pics, your louvers are pointing the wrong direction. They're directing falling rain into the vent...
    – Huesmann
    Sep 21 at 13:18
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    @Huesmann I thought that too at first but looking more carefully I think the 3rd picture is just tilted funny.
    – aquaticapetheory
    Sep 21 at 13:32
  • @aquaticapetheory no, if the louvers were the right direction, we couldn't see inside the vent from above.
    – Huesmann
    Sep 21 at 13:33
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    They aren't the wrong vents. They're just installed incorrectly, both with respect to the steel roofing and with the gobs of tar covering the actual drainage path. You can infer how they're supposed to work from the photo of the underside.
    – isherwood
    Sep 23 at 1:31

1 Answer 1

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A local roofer came by and said the vent caps were installed incorrectly. He said the bottom plate (the wide one) is supposed to be UNDER the roof, not over it. He recommended replacing the caps altogether and installing them correctly and caulking them, not using tar but using silocone based caulk. Apparently tar is not appropriate for metal roofs because they expand and contract so much.

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