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I want to add a second outlet to my finished garage ceiling, about 14 feet from the existing box. The DIY info I found has all been about adding wires to finished walls.

The question is how to get past joists in the ceiling. If these were studs, then I would put a pumpkin cut in the wallboard next to the stud and drill a pass-through hole in the stud. I wouldn't expect any significant weakness to be added. But I think the ceiling joist may be different, since these joists appear to be part of a truss and are under tension. (Probably not a lot, but I want to be code compliant when I make holes.) I don't know the dimensions of the joists, but I'm guessing 2x10 or 2x12. The picture below shows construction over a much smaller room, where I had a pinhole leak in the pipe.

If I were to do this so it complies with construction and electrical codes, what codes would I be looking for? Apart from that, what is the recommended method for passing the wire through or around the joist in a finished ceiling?

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  • This answer might be helpful.
    – Tester101
    Commented Oct 20, 2014 at 15:44
  • It's not really electrical code (which is happy if you are at least 1-1/4" from the edge of the framing) it's a structural issue.
    – Ecnerwal
    Commented Oct 20, 2014 at 18:27

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I guess the first question would be if you have a engineered truss system or ceiling joists; they aren't the same thing (as I've learned).

Is there livable area on top of the garage or an attic/loft?

If they are just ceiling joists you can drill a hole right through the middle of the joists (don't cut out notches). I've done 3/4 inch holes with an auger bit; it would fit two 12/2 wires nicely. Try to keep the holes near the middle.

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    "the middle" is important here - any holes should be in the middle 1/3 of the joist, where the stresses are lowest.
    – Ecnerwal
    Commented Oct 20, 2014 at 16:01
  • Yes, there is a very large living space (a single "great room") above. If it's built the same way as in the picture, I figure it is just joists.
    – Jim
    Commented Oct 20, 2014 at 19:03

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