I’ve pulled Interior Alt and residential electrical permits. I framed an unfinished portion of my basement and I’m preparing to rough-in 12-2-2 cable through the stud cavities at approx. 40” above the floor, with 1-3/4” setbacks to the tangent of 3/4” holes. I will then have my pre-close-in and rough electrical inspection performed. Then I will cover the studs with OSB sheathing and surface-mount RACO #232 4” square metal boxes at 48” off the floor to the vertical centers of the boxes. The first outlets on each circuit will be GFCI’s and feed a string of surface-mounted outlets no more than 6’ apart. Then I’ll wire it all up and pull the final inspections. I have reviewed the IRC (specifically chapter 39 and did not see any reason for concern for my plan). Sound reasonable? Thank you.

  • 2
    Depending on workshop layout (and use) you might want to bump the boxes up a few inches anywhere you might want to lean 4x8 sheet goods against the wall so the top edge of the sheet does not sit across the outlets, but rather just below, leaving the whole outlet box exposed above the 4 foot sheets.
    – Ecnerwal
    Commented Apr 29, 2022 at 22:10
  • 2
    FWIW, in my basement I did something similar with three circuits. The boxes are color coded for the three circuits and cycle along the wall: purple, orange, red, purple, orange, red, ... . That way I can easily plug devices into separate circuits, e.g. a dust collector and router, without having the startup surge on both hitting one breaker. I also do some electronic work and it lets me keep that on a separate circuit from the motorized equipment.
    – HABO
    Commented Apr 30, 2022 at 3:06
  • 1
    Nice, HABO. I’m actually going to run two strings of 12-2-2 in parallel around the room. Receptacle boxes will alternate between the two pairs of 20A circuits: Box 1 - A/B, Box 2 - C/D, Box 3 - A/B, Box 4 - C/D, etc. I normally work alone so this is overkill for me alone, but buddies at work may be coming over to play with my shop toys so it’s feasible that I could consume more than 40A if I only left it to a single strand of 12-2-2. Grandpa used to say, “Too much is no good, but plenty is alright.” :-) I like the idea of color coding — I’m gonna steal that idea. Commented Apr 30, 2022 at 12:33
  • For a few common colors you can actually color code the receptacles themselves without excessive expense. Unfortunately after those few, more colors can be had, but they are absurdly priced. Ivory, white, brown, sometimes black, sometimes gray, and then it gets expensive and/or special order-only...so painting the boxes or faceplates is less expensive.
    – Ecnerwal
    Commented Apr 30, 2022 at 17:08

1 Answer 1


Fitting two GFCIs in a 4x4 box is an extremely cramped install which will be frustrating. For one or more GFCIs in a 2-gang layup, you are better off using a 4-11/16" (120mm) square box such as a Raco 257PL. That will give you the "elbow room" to fit the GFCIs easily. Fit them to a domed cover such as Raco 857.

enter image description here

See all the extra room?

Raco 232 is a welded steel box, I would favor a drawn box as they are much tougher and somewhat more aesthetic. Several makers produce them, not Raco, like a Topaz D4451 or Garvin 52171-SDR.

You don't seem to have a plan for entering the back of the 4x4 boxes. You will need a cable clamp/strain relief listed for the cable.

I know you don't want flush mount for some reason (conduit continuing out the sides?) but you could always flush-mount a box, have the cables enter the side of the box as in normal in flush-mount installations, and then install an extension box on top of them to give you an effective surface-mount box. You could do this either by flush-mounting the metal box and using a normal extension, or by using a "mud ring" to come through the OSB and then a "4x4 on top of 1-gang" box like Hubbell 187.

Cubic inches are a problem, though

Aside from the practical problem of fitting GFCIs in 4x4 boxes, you also have a statutory problem with cubic inches for any kind of receptacle. I count

  • 4 wires in
  • 4 wires out
  • 1 count for 1-4 grounds
  • 1 count for all cable clamps
  • 4 counts for two receptacles

That is 14 wire counts or 31.5 cubic inches. A little bit too much a 4x4 deep box (30 cubic inches).

  • A 4-11/16" (120mm) box is 42 cubic inches (solved).
  • You could flush-mount a 4x4 deep (30 cubes) + surface mount a 4x4 extension box (+21 cubes).

That will also give you breathing room if you ever want to fork something off of this, e.g. using the side knockouts which you will have due to surface-mount.

  • Per your great advise, I will bump up to a pair of 4-11/16” boxes for GFCI’s. As for entering box rears, I planned to use 1/2” Hubbell-Raco 2711B5 Squeeze Connectors since they’re good for 2 separate 12/2 romex, I figured they’d be fine for 12-2-2 romex penetrating through the OSB sheathing and coming through the backs of the boxes. Why surface-mounting? I already bought RACO 232’s and domed covers, and there’s no easy way to flush-mount them. Plus I’d have a lot more work “cut out” for me trying to cut the holes in OSB. Surface-mounting = faster & easier. Does thIs sound ok? Commented Apr 30, 2022 at 2:23
  • 3
    @riffin-rich -- I'd take the 232's back and get drawn boxes instead for a surface-mount app -- welded boxes are only really suitable for flushmount as they have fairly sharp exposed corners Commented Apr 30, 2022 at 4:15
  • @ThreePhaseEel, I shall follow your and Harper’s advice. Commented Apr 30, 2022 at 12:35
  • I wired my workshop in a similar fashion but I used conduit. Then at each 4x4 I used two duplex outlets, each on a seperate circuit. Like you the first in the string had the GCFI. Works real nice when using the table saw, the vac plugs into the same outlet box but in the other duplex.
    – Gil
    Commented Apr 30, 2022 at 16:19
  • 1
    Minor point: Surface mount boxes with cables normally use external cable clamps that don't add to box count. But surface mount boxes also make using conduit (and losing the ground count as well as the clamp count) make sense, IME.
    – Ecnerwal
    Commented Apr 30, 2022 at 17:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.