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How far from the end of a 2x12 or 2x10 floor joist can I drill a hole? NEC 502.8 does not give this answer, only that you have to be 2" above or below the edges, not in what part of the span it has to be in.

  • There are no restrictions as to where along the span you can bore holes in sawn lumber joists. – Tester101 Oct 27 '15 at 15:26
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    Code restrictions aside, if you have flexibility it is best to make the holes no larger than necessary and have them along the centerline of the joist. – Hank Oct 27 '15 at 15:54
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    But note that there are very strict rules for various types of engineered joists. These can be found on the manufacturers website and apply to structural integrity rather than electrical rules. – bib Oct 27 '15 at 17:40
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The rules that I know for holes (not notches) are to keep your hole in the center of the joist when possible (top to bottom) or at least 2" from an edge, round, with a diameter less than 1/3 of height of the joist. Once you follow those, I don't believe there's a restriction on how close or far from the end of the joist you can install the holes. Personally I would keep the hole at least the length of one hole diameter (or 2" for small holes) away from the end of the joist, but there isn't anything in the building code I see requiring that.

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    hehe "install the holes". – Tester101 Oct 27 '15 at 15:18
  • +1 for round holes. I used my triangle bit and got flagged once. – DMoore Oct 27 '15 at 16:03

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