Drilling beams / wood construction


Senior Member
Berthoud, Colorado
Journeyman Lineman / Distribution design and EC in my spare time
One thing I have never been sure on... I know you are not suppose to drill micro lam beams. This place I am working on has a fairly large beam running down the center and the rafters tie into this beam to hold the roof up. The beam will be exposed and I need to mount a ceiling fan to the bottom. You and I both know drilling a hole to fish the wire through will not hinder the strength but I am wondering if inspectors can call you on that?


Senior Member
I would not drill it if it was my house.
I would. I would drill a 2" hole up through the beam and then cut a big notch in the bottom of the beam to recess the box and not one of those pancake boxes either and I would use a chain saw to do it. I'm trying to get a head start on my insanity defense ( just in case ).

Back to sanity for a moment. I think I would request the GC or owner get a structural engineer to come up with a route for the needed cable and box mounting.


Senior Member
I don’t guess exposed BX is an option...
go for the industrial look.


Master Electrician Electric Contractor Richmond VA
Henrico County, VA
Electrical Contractor
Here's what I would do, and have done: drill a 1/2" hole from the bottom of the beam, at a slight angle toward one rafter side, where it will emerge through the side of the beam above the rafter bottoms, so it will be above the sloped drywall. I did use a pancake fan box, because the beam was going to be drywalled.

The reason I have the pic is because we, being licensed for home and commercial improvement as well as electrical, actually built the entire addition, a 16' x 25' master bed/bath suite. The ridge beam is made up with three 2" x 14" micro-lams, which share the load, implying that I believe the 1/2" hole is not an issue.

I have a lot of before, during, and after pics, but not one that shows the beam penetration. These show the addition from the outside:

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