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I plan to add some lighting in positions on the ceiling that doesn't have nearby wire available.

The there is no free space between the ceiling/roof in which to run a wire (there's the wood, then solid foam block insulation, then weather barrier, then the shingles). So, I would need to run wire (12/2 or 12/3) to that location somehow. I'm aware of Wiremold, but that wouldn't look very good with the style and material of the ceiling itself.

Is it possible, instead, to run the wire through a 0.5" channel routed out of a 1x1" piece of wood and affix that wood to the ceiling? I read through California electrical code (I'm in San Bernardino County, California), but didn't see anything specific around this (unless I missed it, or interpreted it incorrectly).

Thanks in advance.

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  • What sort of finish are we talking about on the ceiling?
    – ThreePhaseEel
    Apr 8, 2021 at 0:49
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    This solution seems interesting. You might want to consider it. thisoldhouse.com/electrical/21016030/…
    – r13
    Apr 8, 2021 at 2:11
  • @ThreePhaseEel it's tongue & groove cedar boards. Directly above those sits the foam block insulation. They're very tightly pressured together. The finish on the boards is clear gloss, and there are three sets of structural beams that form the A-frame shape of the ceiling. There is no attic.
    – Matthew
    Apr 16, 2021 at 1:35

5 Answers 5

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No, you can't do it unless there's a "nail plate" to protect it from physical damage (nails).

You could mill it out to 15/16" and lay in EMT metal conduit. It has the thinnest wall of any conduit and will provide the needed physical protection. Use that either simply as a damage shield in the vulnerable area, or if able, as a full-on wiring method for the entire route.

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  • I was just going to write this. Just did it in a basement where we were hiding a metal pole in the wall and working around the i-beam... Come on let me answer the softballs. And you can hit the back of the trim with a planer on just half - much better to do the inside half.
    – DMoore
    Apr 8, 2021 at 3:20
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    Oh you should see some of the stuff we have/had in my country. When I first started going out with my wife a number of 40W light fixtures in her apartment were run using twin flex cable affixed to the wall with small floorers nails which were nailed through the middle of the plastic coating. It was the kind of twin flex cable that used to be used mostly for phone lines.
    – DRF
    Apr 8, 2021 at 14:21
  • Great idea. So, basically, I would route out a channel in the wood piece, secure the EMT metal conduit there, and that would be alright? I'd be running something like 8–12 led lights split between two of the "trim/EMT" runs (one per beam). So far, this seems like the most viable option.
    – Matthew
    Apr 16, 2021 at 1:15
  • @Matthew -- yeah, the EMT would basically be continuously secured by the channel
    – ThreePhaseEel
    Apr 16, 2021 at 1:39
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Yes it's possible but it wouldn't be code compliant if it's 120v. Wires must be 1-1/2 inches from the surface so that you won't hit them by mistake with a screw or nail. If you had some sort of metal conduit you could do it. Low voltage wiring is fine.

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  • Isn't that what I said "if you had some sort of conduit you could do it?"
    – jonathan
    Apr 16, 2021 at 21:36
  • Sorry, missed that in your asnwer
    – ThreePhaseEel
    Apr 16, 2021 at 23:15
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If your foam block is multiple layers deep sometimes it's possible to run a fish tape between layers. Take off the leader if present, use a blowtorch to heat the fishtape and fold about 3"(75mm) tightly back on itself (no loop), tape tightly together starting 1" down from the tip, stretching the tape slightly and use only 1 layer if possible. Use a file or sandpaper to smooth the tip if necessary. 1/4" or 3/8" fish tape is better for longer runs. If the fish tape is curly, straighten it first with a fish tape straightener. Take care and use both hands to feed the tape in, one hand pushing from about 18"(450mm) away and the other hand close to where the fish tape enters to redirect the force. For long hops, especially if you have to fish through partial obstructions, a toner is useful to locate the fish tape in the ceiling. If you get it close but a small amount (<3f(1m)) to the side of the destination, usually you can cut a hole at the destination and hook it over with a second fish tape.

If you can get a fish tape through, usually an armored cable can be drawn in. You can untape the head to use as a pull loop (don't try to unbend the tip, just cross the wires through the loop and fold back 4-6" and tape tightly from 2" onto the armor up to 2" past the folded back fish tape and back, 2 layers to reduce friction. The armor should be stripped enough that the folded back wire does not pass over armor). Note before starting that armored cable pulls nicer in one direction. The armor coil should end on the outside on the end you are feeding in. The person feeding the cable should feed as described above, and the person pulling should do the reverse, with the far hand providing pulling force and the close hand redirecting the force to pull flat between the sheets rather than down into the soft material below.

You may need an electrician to do this for you though depending on where you live.

Also consider that wiremold can be refinished many ways to be more aesthetically pleasing. Real wood edge laminate would probably give you the look you want. For short hops and hanging fixtures you can also consider hanging fixture wire strung through nice chain.

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  • Interesting idea. I checked the spacing, and the foam block is quite firmly pressed against the wood of the ceiling. I haven't seen fish tape firm enough to push through that. I think also that armored cable would have quite a bit of pressure on it if I were somehow able to manage feeding it through. Thanks for your suggestion on this. I'll chat with a couple local electricians.
    – Matthew
    Apr 16, 2021 at 1:11
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    Usually only electricians have the wider more fish tapes because of the specialized use. I have one that's technically a plumbing fishtape for plumbers to use on dugouts. If the pressure isn't too much to squeeze the fish tape through, you basically need one wide enough to stay flat and go straight and with a head rigid and smooth enough it won't turn and puncture the foam. Going between foam and wood may not be OK if screws or nails are likely to be driven through the wood at a later date. I've done dozens of extra difficult fishing jobs like this. The longest was 19.5 man hours.
    – K H
    Apr 16, 2021 at 1:23
  • Usually once you get a few feet in you have a good idea of how well things are going to go.
    – K H
    Apr 16, 2021 at 1:26
  • I just tried again with the fish tape I have. It's flat, but not super wide, maybe a quarter inch. Seeing some of the other areas of the house (screw or nail points protruding), I think it might be best to try a safer route. 19.5 hours sounds like a lot haha. I'd put in the time if I felt more sure about the nail/screw situation.
    – Matthew
    Apr 16, 2021 at 1:32
  • I was just a first year apprentice, so I was given the job because I was cheap and skinny. After the first two hours I was completely disheartened and didn't believe it was possible, and I called my boss to tell him we should give up. We absolutely needed the wire and the cost to remove the pre cast concrete panelling and put it back in was estimated at around 50000-100000 currency units, any my apprentice hours could just dissappear into other parts of the project so they could look at my work as 0 cost (not ethical, but common).
    – K H
    Apr 16, 2021 at 1:38
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Can't say 100% certain with respect to code, but I did something very similar, with agreement of my electrician. He fished NM cable from bathroom lighting up to attic and through a hole to peak of ceiling between kitchen and dining room, around 8 feet along ceiling, then into ceiling to get to middle of dining room for new chandelier. I covered the 8' section with a piece of molding from Home Depot and it looks like it was always there.

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It might require a larger trim than you were thinking but have you considered just increasing the space in trim to accommodate the wire mold? This should be doable with pretty typical crown molding. If you need to run across the ceiling you could add a coffered ceiling which can look really nice.

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  • This is an interesting idea. Would that be compliant? I figure the Wiremold is pretty small, and so it wouldn't really be that hard to route out a channel large enough to fit the Wiremold into in a wood piece. My ceiling is very close to A-frame, and this is part of the challenge since there's no attic to run the wires through.
    – Matthew
    Apr 16, 2021 at 1:06
  • I'm not 100% sure on the code but if the wire mold is steel, it would seem similar to Harper's suggestion of using a conduit. I don't think plastic would be OK because it wouldn't protect the wiring enough. I would defer to some of the other contributors here who know the NEC better than I. Harper or manassehkatz should be able to confirm of deny.
    – JimmyJames
    Apr 16, 2021 at 15:28
  • The other thing you can do is go all in on the coffered ceiling or faux (hollow) timbers (which probably looks more natural in an A-frame) and then you have plenty of space to run conduit. If the 'timbers' are large enough, you might be OK with NM even.
    – JimmyJames
    Apr 16, 2021 at 15:32
  • Something like this: homedepot.com/p/…
    – JimmyJames
    Apr 16, 2021 at 15:34
  • That's a 'faux beam' which is also 'faux wood' which is fine if you like the look but it's the fake beam, not the fake wood that's the point here.
    – JimmyJames
    Apr 16, 2021 at 17:41

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