I've been working on wiring my shop in my unfinished basement (sub-panel installed by a licensed electrician) and I've come across a question I haven't been able to find an easy answer to.

There are places where I'm running down the length of a floor joist (at least 1.5" from the bottom edge, secured every few feet) and I need to change the side of the joist bay (to go through a hole in the joist usually). It's a simple crossing of the open air space between joists. Are there any code requirements or rules on how to cross the joist bay if the wire continues to run parallel to the joist for a bit on either side of the crossing?

I live in Ohio if that matters for the answers.

Thanks for the help!

  • 1
    In most places, code requires cable to be secured at least every 4 feet (maybe 4.5 feet). It's a very common practice to drill thru joists to run cables. Not more than 3 per hole (I got snipped by an inspector on that one....my mistake). Running cable thru drilled holes in joints is considered "supported". Sorry for the long comment, but you're fine, just staple it near either side where it crosses. No biggie. Dec 30, 2020 at 13:15
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    Answers go down there, George.
    – isherwood
    Dec 30, 2020 at 16:29
  • Every 4.5’ for NMB securing the 8” rule from 314.7 and a minimum of 1-1/4” away from the surface, unless surface mounted.
    – Ed Beal
    Dec 30, 2020 at 16:35

2 Answers 2


As @George stated, running between joists is fine. Just don't attach to the bottom of the joists. That is not fine.

One finer point, by the way...make sure you drill your holes in your joists within the middle 1/3 of the joist. Don't do it 1.5" from the bottom of the joist.

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    You actually can attach to the bottom of a joist, I have done this many times when there is insulation I do not want to disturb going parallel. Also going perpendicular is also allowed see exhibit 300.2 in the NEC. That’s for enclosed for exposed see 334.1.
    – Ed Beal
    Dec 30, 2020 at 16:30

As far as rules an inspector will usually require a staple when crossing at each side. They will quote a neat and workmanship like manor and that cables going into a box without clamps have to be stapled within 8” but other than that following the floor joist is loosely defined.

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