If the junction box on a recessed light is too small, is it okay to use a box spacer to add a second junction box to it? This would allow adding a second junction box, that pulls down in the exact same way as the junction box on the recessed light itself. box spacer

The wiring that would go in the box would be (if there wasn't a second box): 4 wires for what used to be a two switch fan. This will control 2 zones of recessed lights. 2 wires and a ground go out to another zone of lights 2 wires and a ground go out to a light on the same zone 2 wires and a ground go out to another light on the same zone (the light was in the middle) 2 wires go to the can light itself.

It think that is 12 14 gauge wires for box fill calculation, and the largest junction box I can find on a recessed light housing is about 21 cu. in.

With the box spacer a 30.3 cu. in. 2 gang junction box could be added to handle all connections except the can light itself.

It would be just as accessible as if all the connections in the can light's junction box, as the new junction box would held by the box spacer.

United States. Looks like city uses nec 2017..

30 cu. in. 2 gang junction box

  • In terms of legalities and code, I suspect you should tag this with your country.
    – user101382
    May 31, 2021 at 18:22
  • In United States.
    – John
    May 31, 2021 at 18:28
  • You should edit the question and add that to the text, and possibly add a tag as well.
    – user101382
    May 31, 2021 at 18:28
  • I take it you'd rather not have a separately accessed junction box in your ceiling to make the splices in? May 31, 2021 at 20:57
  • Yes. I was hoping to avoid that. I had seen some debate whether it is okay to just put a junction box on the joist behind it. I figured this way gets rid of access problems, but I didn't know if there is a spot requirement.
    – John
    May 31, 2021 at 21:15

1 Answer 1


Absolutely you can make all your junctions in a “4 square box” connected by a coupling connected to the light box ( IF IT IS ACCESSIBLE !) Now you said recessed and we would to know if there was attic access.. for 2020 code. prior to 2020 code a ceiling box fixture allowed access was considered accessible, the 2020 code changed that so my answer stands by the code you are governed by. My belief is 2017 is it was allowed by the NEC but not in the 2020 version.

  • So no need to worry about supporting the junction box connected to the recessed light junction box through e the spacer?
    – John
    Jun 1, 2021 at 3:51
  • Or better just to attach the junction box to a stud?
    – John
    Jun 1, 2021 at 4:02
  • 1
    If you have access it is best to anchor the box as long as accessible a strap from the fixture to the box was legal in 17 but not in 20 for recessed unless accessible from an attic for example. Yes support is best.
    – Ed Beal
    Jun 1, 2021 at 5:41
  • For future reference and not in an attic, under the 2020 rules would the junction box held by a spacer be acceptable?
    – John
    Jun 1, 2021 at 12:44
  • 1
    John the conduit as a support won’t pass inspection in most jurisdictions a strap or stud mounting is usually required.
    – Ed Beal
    Jun 1, 2021 at 17:09

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