I'm trying to understand 334.15 Exposed Work: "Where cable is run at angles with joists in unfinished basements and crawl spaces, it shall be permissible to secure cables not smaller than two 6 AWG or three 8 AWG conductors directly to the lower edges of the joists. Smaller cables shall be run either through bored holes in joists or on running boards".

  1. When they say smaller do they mean in diameter or by gauge number? I want to run 6/3 with ground NM on the ceiling of an unfinished basement.
  2. Are they also saying that I can run 6/3 perpendicular to the joists attached to their underside without running boards?

1 Answer 1


It means actual size, not designator number.

6/3 is larger than 8/3 or 6/2, you do not need to bore holes or use running boards on the ceiling. Running down a wall requires protection.

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    The OP says it's an unfinished basement. If there is any chance the OP or subsequent owner would want to finish it, that cable would be in the way. If practical, I'd consider running thru holes in the joists, just to keep it out of the way and well supported. Not a big deal, just trying to help future-proof it. May 22, 2021 at 14:23
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    @GeorgeAnderson Sometimes I wish to provide an alternative to some tldr answers and just try to answer the question asked. The NEC allows things that aren't always best practice. If practical I would definitely make drilling the joists my first option. Second option would be installing with a (secured) extra loop providing slack to provide it could be repulled later if desired. May 22, 2021 at 14:38
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    Yes, it's sometimes just a judgement call when to just "answer the question" or go on with additional advice. That's why I didn't post this as answer, just a comment. I agree with your answer, BTW, I just wanted to offer my suggestion to potentially save some pain later! + May 22, 2021 at 20:16

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