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I am trying to determine if my house is up to code with respect to some holes that I found bored in the ceiling joists. The holes are about 1 inch in diameter and at least 2 inches from the top and the bottom of 2x10 joists. The holes were bored to run a NM electrical cable. The specific aspect I am concerned about is that the holes are very close (< 2 inches) to the end of the joist where it is bearing on the beam.

I read various notching and boring guides and they all specify 2 inches from the top and bottom but I can't find any guides that talk about how close they can be to the end of the joist. I assume that having a hole in the area that is bearing on the beam would weaken the joist but I am having a hard time finding the rules on this.

  • I've read code that specifies that no holes should be in the center third of the joist, but no mention of holes in the ends of joists. – Edwin May 12 '14 at 2:47
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    The information in this answer might be useful. – Tester101 May 12 '14 at 10:43
  • @Edwin, I believe the center third rule only applies to notches, not to holes drilled in the center of the joist. – BMitch May 13 '14 at 12:22
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I spoke to my structural engineer and the answer is that it depends on the depth of your joists. In my case, where I have 2x10 joists there is no problem with a small (1-inch diamater) hole on or near the area where the joist is bearing on its support beam. Basically the same notching and boring rules apply at the end of the joist: 2 inches from top or bottom, etc..

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