I'm currently remodeling my kitchen. Instead of a cooktop hood, I plan to re-use the existing ceiling exhaust fan. It looks to be about a 8" diameter fan that is inside a 10x3.25 duct that exhausts outside. The fan motor is shot, I will need to replace it.

The issue I have though is when I removed the bulkhead (see post here), it was revealed that I had a leak from that exhaust duct. From the outside I can see that the exhaust flap is stuck partially open, and from the inside I can see the duct has some openings where moisture can run down onto the 2x10 my floor joists rest on.

My intention is to replace the fan and replace the exhaust flap, however, I cannot find a new exhaust flap that is intended for 10x3.25 duct to exhaust outside. I'm thinking that's an usual setup. But given that I now have this opening in my masonry outside, I need to fill it, and I'd like to use it. Where should I look for a replacement/what are my alternatives?

A secondary question - I assume there is no chance I can find a replacement motor for what is probably a 1940's exhaust fan. Is there a common/standard size that maybe I could only swap the motor? Or is my only solution to cut out the drywall and the duct and install a new exhaust fan box?


Exhaust outside the house Duct exiting the house Exhaust fan

  • It's unlikely that enough moisture to do what we see there came in through the flap unless you're in hurricane territory. Those are mostly for air stoppage. My guess is that the seal around (above) the vent leaks (or did).
    – isherwood
    Jun 26, 2019 at 13:59
  • Any recommendations for sealing compound for masonry to galvanized duct?
    – DrTarr
    Jun 26, 2019 at 14:31
  • Urethane caulk. About the best stuff there is. Use caution as it doesn't come off without great effort, including skin.
    – isherwood
    Jun 26, 2019 at 14:41

1 Answer 1


10 x 3 1/4 seems to be a standard size. Any big box store should have them. enter image description here

  • My mistake, for some reason I was searching exhaust vent and all I could find was round connections. Thanks
    – DrTarr
    Jun 26, 2019 at 14:30

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