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  1. #1
    Join Date
    Jul 2008
    Posts
    34

    Default Bathroom fan exhaust

    I just put in a new bathroom exhaust fan that I will be exhausting to the exterior wall. The pipe is 6". I have 8" exposed siding but the only size I am able to find for the exhaust cover is 9". How do you handle the overlap in siding or is that not of a concern?

  2. #2
    Join Date
    Aug 2007
    Posts
    7,039

    Default Re: Bathroom fan exhaust

    If possible, I would try to tuck the top of the exhaust cover below the bottom edge of the siding so that it sits fully on one piece. This would allow caulking of the most important top and side areas. The bottom can also be caulked or install a small shim to fill the gap and then caulk both the shim to the wall and the cover to the shim.

    If you can't do the install like that, then install however, then either use foam caulk backer or cut a wood shim and caulk everything to seal against critters and water intrusion.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  3. #3
    Join Date
    Jan 2010
    Location
    Northern Virginia
    Posts
    1,172

    Default Re: Bathroom fan exhaust

    You would cut out a portion of the siding, say 10 or more inches square, and install a plaque of wood, thicker than the thickness of the two laps of siding, and cut your duct-port into that. Ideally, if very exposed, you would add head-flashing at the top so water couldn't enter, and a small rabbet at the bottom overlapping the siding 1/2" or so would complete the water-detailing, after you caulked the edges.
    S_M
    Remove not the ancient landmark, which your fathers have set.

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