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Basement bathroom exhaust duct loop

John_H12 | Posted in Mechanicals on

I need to install a bathroom exhaust fan in my basement.  I’m near the steel support beam (5 feet away) that supports the middle of the I- joists.  The I joists are continuous over the support beams.

I’m concerned about putting a 3.5 inch hole through the I joists.  I’m equally concerned amount putting a p- trap in the exhaust duct.  See the attached drawing.


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  1. Expert Member
    Malcolm Taylor | | #1


    Th installation manual of whatever I-joists you used will have instruction for where and how big holes in the webs can be. They are all available online. My bet is you will be fine with a 3.5" hole.

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