I discovered some seemingly-inefficient wiring and a hidden junction box in the wall. I understand why they would put it there, but it still seems inefficient. I think the same could be accomplished differently, eliminating the need for the junction box or possibly relocating it at a normal outlet height, but I'm not sure how.

I've drawn out the wiring diagram.


  • Fixtures
    • L1 = Exterior light fixture 1
    • L2 = Exterior light fixture 2
  • Switches
    • S1 = Switch that should control both exterior lights (L1 and L2)
    • S2 = Empty slot for a switch
    • S3 = Switch for ceiling fan outlet
  • Junction boxes
    • J1 = Round junction box 1 (no access, faces outside, this is what I want to remove, or relocate at normal outlet height, if possible)

Some important notes

  • Yellow and orange are on different circuits. I don't want to add anything to the wall heater line. I put it here for reference only.
  • Right now, the yellow and orange lines are 12/2. I can replace whatever is visible, pretty much. But, I prefer strongly to avoid replacing the wire bringing power into the first exterior outlet (it runs behind stone and access is only possible if I remove major sections of the exterior wall on the left side of the house). I also prefer to avoid re-running wire number 5; it's not as hard, but it would require me opening up the right side wall to find the next endpoint.
  • Since S2 is empty, I would like to use this for additional interior light control. But, those lights aren't installed yet. They would tap into line 5 (on another wall).
  • Due to L1's (and stud) position, there is almost no room behind L1. So, it has to use a pancake electrical box. There isn't room in that box for much.
  • Similarly, due to the stud position, the switch boxes for S1 and S2+S3 are a tight fit in those spaces. The space between studs where S1 is located cannot fit more than a single gang box. The space where S2+S3 is located cannot fit more than a 2 gang box.
  • Not shown are the horizontal fireblocks. I mention this since the hole currently can fit 3 12/2 or 12/3 wires alright. Unless I'm not mistaken, local code limits NM-B per bored hole to 3.
  • Number 5 run continues into the next side wall. It's not an end run. I don't want 5 to be switched.
  • I do have access to the crawlspace. I haven't run wire in a crawlspace before, so I'd have to figure out what the code is for that. I prefer to avoid doing this, if I can.
  • NM Cable Splices aren't compliant in this case (based on local code requirements).

Note that I wouldn't mind relocating J1 junction box underneath the switches (i.e., outlet height). But, that would put it under the fireblock and I'd need to keep the wires going through there to 3 or less. This seems necessary either way if I need to make the junction box accessible without it looking ugly inside.

Any recommendations here?

tight space inefficient wiring buried junction box

  • How deep are the S1-S3 boxes? Also, what edition of the NEC are you on, and is it an explicit local amendment that prohibits the use of NM splice/tap devices, or...? Also, is moving L1 an option? Jan 18, 2021 at 0:29
  • @ThreePhaseEel Thanks for the questions! [S2/S3] is in one, dual gang metal box that is 4x4x2 deep. S1 is half that size. Both boxes are metal. I'm on the 2017 NEC. Those splice/tap devices are only allowed when doing a repair, and would be excluded in this case... or so I'm told. L1 is positioned in exact center between door and window. I would like to avoid moving it if at all possible.
    – Matthew
    Jan 18, 2021 at 1:28
  • More specifically, I'm on 2017 NEC, with some local adjustments. The splice/tap device allowed usage for NM cable is referenced at 334.40(B) in the online version of the electrical code (page 244 of 1036). That is, unless I'm reading that incorrectly.
    – Matthew
    Jan 18, 2021 at 1:35
  • I had thought about putting a junction box earlier, ahead of the first exterior outlet. From that junction box, maybe I could run power into L2, then run from L2 to S1, then from S1 to L1. So, then I could reuse the 12/2 that's there, right? Still, L2 would be a very tight fit in that pancake box. I wonder if there's a way to have L1 and L2 be at the end of a run while accomplishing the rest of this?
    – Matthew
    Jan 18, 2021 at 1:46
  • Can you provide us a link to your local amendments? Jan 18, 2021 at 2:02

1 Answer 1


I'd make the argument that this is indeed repair work in the scope of 334.40

Even taking the NEC 334.40 restriction on concealed use of NM splicing devices as limiting them to repair work in existing wiring, I'd make the argument that this is a repair, as it's fixing an existing Code noncompliance in an existing building (vs. simply expanding on Code-compliant wiring).

Once you do that to extend cable #5, you can then blow the S2/S3 box out from a 4" square box to a "5S" (really, just under 4¾" square) or a true 5" or 6" square box, preferably one with at least 3" of depth. That should get you enough cubic inch capacity to land the cable #5 extension, as well as a 12/3 replacement for cable #3, cable #6, and a new cable for the new light, in the S2/S3 box and make all the splices there. A replacement for cables 4 & 7 is then run over to the S1 box from L1, which makes the wiring for L1 straightforward, while the red wire in the replacement for cable #3 carries the S1 switched-hot back to the S2/S3 box where it can go to cable #6 to feed L2.

As to getting the new cable up thru the top plate? Well, one could cross it over the into the other stud bay by running a 12/4 instead of the 12/3 between the two switch boxes and then running the new cable up from the S1 box, but that may require a deeper box at S1 as well as replacing the S2/S3 box with something chunky. It also should be possible to have 2 holes in the top plate and/or fireblocking in the S2/S3 bay, with the cables split between the holes.

The alternative if you can't use the NM splice on cable #5 would be to "flip" the J1 junction box to the inside wall at its current height, given that rerunning cable #5 is off the table. One could disguise it with a nifty wall sconce or such if one wished, even; I'd use a deep 4" square or "5S" box for this job as one can put a single-gang mud ring of the appropriate size on either.

  • Thanks very much for your help. I tried a larger box, but I misjudged the space available. Unfortunately, the larger box doesn't fit in that space. So, I'm thinking of some additional workarounds.
    – Matthew
    Jan 19, 2021 at 0:46
  • The idea of masking it with a sconce is actually really good. I didn't think of that before.
    – Matthew
    Jan 19, 2021 at 0:50
  • @Matthew -- what sort of larger box did you try? Jan 19, 2021 at 1:26
  • I purchased several boxes, trying both plastic and metal, and in increasing sizes. Nothing more than the 2 gang box fits. The next largest size wouldn’t fit in at all. I wonder if it makes sense to mount the two gang further back, and get an extender? Although, with the taper, I’m not sure it would actually increase space by much.
    – Matthew
    Jan 19, 2021 at 12:02
  • @Matthew -- are you just going up in gang size, or did you try a larger square box as well? Jan 19, 2021 at 12:26

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