Porch light wiring under ceiling/roof joists code question

Discussion in 'Electrical Forum discussion & Blog' started by joseph skoler, Jul 17, 2021.

  1. joseph skoler

    joseph skoler Member

    Joined:
    Jan 14, 2018
    Location:
    Sullivan County, NY
    I have a covered porch framed and will be installing either beadboard or a 1x4 style porch ceiling.

    I am installing recessed LED light pucks in the ceiling.

    I need to run 12/2 NM across the joists but I don't want to drill holes -- they are only 2x6's 8" OC (don't ask).

    How can I do this and meet code?

    I ran the wires in the picture below, but I don't know if it will meet code.

    Thank you!

    64821771133__2B9F7EFC-F500-4D01-B00D-4337117CA234.jpg
     
  2. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Looks OK to me if you are going to cover the NM at the top of the siding with a large crown molding without risk of hitting the NM. Some of the rules on the use of NM cable are a judgement call, so local opinion may differ.

    Drilling the 2x6's would be allowed, you'd just need to hit the center of them with say a 3/4" hole. Maximum allowed hole size would be 1.5" dead center--the hole needs to be 2" clear from top and bottom, and in this case that controls the hole size (which would otherwise be allowed to be 1/3 the member depth). Of course, drilling is hard at 8" o.c. Double 2x6 at 16" o.c. would be a more practical way to arrange those joists.

    Cheers, Wayne
     
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  4. wwhitney

    wwhitney Well-Known Member

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    P.S. The IRC would let you notch the bottom of the joists by up to 5.5/6", away from the central third of the rafter span. And a 1/2" deep x 1" notch notch near the end wouldn't be so awful, although not great. You'd need nail plates at each joist.

    Cheers, Wayne
     
  5. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    As Wayne states, a local inspector may like it or not? I understand you can get heavy snow loads at times.

    In my book there is too much chance of a nail hitting the cable. Drilling a hole really does not lessen the strength of the joist if performed to the industry guidelines. A 5/8" hole would all be needed but a 3/4" is preferred to allow wiggle room and no binding.

    A lot has to do with the way the finished ceiling is going the meet the wall. If you are really set against drilling holes you can use PVC 1/2" electrical conduit with the NMC 12/2 cable inside of it. Just use straight pipe between the runs down the joist. The conduit only needs to be supported every 30" and it will help with nail protection.

    Another way is if you need to drill holes you can use a stud shoe to reinforce the joist and it will also allow for nail protection or a stud plate. Screen Shot 2021-07-18 at 2.07.55 PM.jpg Screen Shot 2021-07-18 at 2.12.18 PM.jpg


    Is this on a 20 amp breaker needing the 12 gauge wire? LEDS take such little power you be less than 50 watts

    Screen Shot 2021-07-18 at 1.52.02 PM.jpg
     
  6. joseph skoler

    joseph skoler Member

    Joined:
    Jan 14, 2018
    Location:
    Sullivan County, NY
    Thank you both very much.

    There will be 20, 14 watt LEDs, which is still only 280 watts (~2.5 amps), but I have the wire.

    I am very much set against drilling holes because the plans called for 2x8, but both me and the contractor misread the (handwritten) plans and installed 2x6's. To correct it (after it was all done), we slid in another set of 2x6 to make it 8" OC. We are still hoping to not have a problem with the town about this. So, the last thing I want to do is compromise even a little the strength. It's a 12' span.

    I don't really understand the PVC option/

    I'd rather hide the wires under molding but we are using square molding (1x4, I think) and I can't really visualize how to do that.

    Nonetheless, I asked a local electrical inspector and he said that what I did was not okay.

    He said either drill holes build a trough, but I don't understand what that would be.
     
  7. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    As for the rafter size, there are tables for that, most likely this one would apply, but you haven't provided all the necessary data to be sure.

    https://up.codes/viewer/new_york/irc-2018/chapter/8/roof-ceiling-construction#table_R802.4.1-2

    The PVC option would be tricky because you have all the runs going parallel to the joists. So you'd need to effectively have 20 holes in the side of the conduit, lined up with the rafter bays that have lights. The PVC would just be enclosing/protecting all the NM that isn't in a rafter bay. And then you'd still want to cover the PVC with a molding or something.

    But apparently you need to further protect the NM cable from damage. So you may need to change your molding plans and cover up a bit more of the top row of siding than previous planned.

    You could attach a 2x4 (or 3x4 if you need the extra depth) flatwise across the bottom of the rafters, almost up against the seat of all the joist hangers. [Or if it really matters, you could rabbet one corner to overlap the seats by 1/2" or 1".] Then you'd trim out the two exposed surfaces of the 2x4. The ceiling boards would butt into the trim on the edge of the 2x4, so you'd run the 2x4 straight even if the wall isn't. The trim board on the bottom would overhang the 2x4 towards the house and butt into the top row of siding, so scribe the board to the siding if the wall isn't straight.

    Cheers, Wayne
     
  8. joseph skoler

    joseph skoler Member

    Joined:
    Jan 14, 2018
    Location:
    Sullivan County, NY
    Well, there do not seem to be any tables that show 8" OC. I've been searching for many, many hours.

    The total linear length of each of 2 rows of 10 lights is 58', so it's really only 10 runs in total down the joists.

    I thought about the 2x4 flatwise, but I hadn't thought about rabbeting the 2x4's near the seat of the hangers.

    Not sure I understand about trimming out the 2 edges of the 2x4. Couldn't I just attach the ceiling material to the bottom flat side of the 2x4's?

    Thank you!
     
  9. wwhitney

    wwhitney Well-Known Member

    Joined:
    Mar 17, 2019
    Location:
    Berkeley, CA
    Sure, but depending on the grade and species, 2x6 at 16" o.c. looks to be sufficient for a 12' span.

    As for finding a table with 8" o.c. members, you won't. The best you could try to do is find a table that is for half of the loads you have, and use the entry for 16" o.c. members. That is, 10 psf dead plus 10 psf live and L/240 deflection for 2x6s at 16" o.c. should be the same allowable span as for 20 psf dead plus 20 psf live and L/240 deflection for 2x6s at 8" o.c.


    I was proposing a single 2x4, rather than lowering the whole ceiling, so you'd have a step at the wall edge of the ceiling.

    Cheers, Wayne
     
  10. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    I thought it looked like a lot of rafters. If the inspector doesn't like the 8" OC 2x6's, you can hire an engineer to rate it for live load and snow load and it most likely will exceed the minimum load requirements. The engineer would have to draw up plans and may have to resubmit the permit. It will be less costly than to redo it but it will take time.
     
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