Is it safe to make a hole through a beam for a vent?

I have a question. I am putting up a bathroom fan. The only way to vent it is to go over or under a 3 ply 2×10 beam that spans 12ft. If I go over or under it will leave a strange boxed area in the bathroom or the room above.

Is it safe to make a hole through the support beam for the exhaust? If so how large of a hole can I make?

Warren Seegers from Indiana

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Great question. And tough problem. It’s puzzles like this that further convince me that bathrooms, pound-for-pound, are the toughest rooms in the house to work on. OK, assuming you intend to mount the fan in the ceiling, I’m going to guess this 3-ply (or triple) 2×10 is a joist or header of some sort and that there is a mondo load on it.

My first move would be to take a second look at fan-mounting locations, notably: Can you mount the fan in the wall and pass through a stud-bay instead? ??If you can’t, I would say that you can’t punch a hole for a vent fan in a structural member as you describe without reinforcing it. MetWood makes steel bracket for this purpose.

Can you get to both sides of the beam? MetWood may recommend a certain bracket for your application, but you have to check with your local code official to make sure their recommendation is kosher for the application.