Really tight space, won't fit dimmer or switch

I’m trying to set up a Red dimmer and switch in an existing gangbox. However, neither of them fit because how it was set up. The electrician that wired the house used two 1.5" open back metal gangboxes. I’m not sure how to go about properly fixing this and need some recommendations. In this image you can see the backs of the other switches on the other side. Any tips or pointers would be really helpful.

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I’d make sure there’s no excess wire for any of the switches. I’d also consider installing a double gang retrofit box and relocate these switches (up or down) if it’s too crowded.

I don’t think I’ve ever seen this scenario.

@Bry -Any tips tricks?

Yeah, this is an odd one for me as well. I’m going to rip into both sides of the wall tomorrow to see what exactly I can see. If it’s a shared line or something even more obscure. The house passed inspection back in '89… I doubt it could again with stuff like this done.

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No tips or tricks unfortunately. If there is enough room in the cavity, I would cut both of those boxes out and replace them with old work boxes. Move one of them left or right and then patch up the old hole.

The only issue is that you may have to add conductors in one of the boxes to extend the reach to the other box if the cables are stapled to the stud and can’t make it to the new box. Box capacities are rated in cubic inches calculated by the number of conductors in the box, primarily. Get as deep a box as you can or if that box will still be too small, use a three gang and put a blank plate in the empty slot.

As @harjms mentioned, you could also relocate one box above or below the current position, which might make it easier without extending the conductors. Some are accustomed to a uniform height, however

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Thanks Bry. Some of the electrical work was done correctly (stapled to the studs). So, I’ll have to definitely move the location to get this to work and replace both boxes. So much fun ahead of me on this project.

I hear ya. Sometimes I just want to punch the electrician. My new to me house, the ceiling light wasn’t centered. Easily noticeable. I thought maybe a joist was sitting there. I took it down and saw no joist in sight where it should be(10” over). I moved it, put in a retrofit box, and now I need to patch the old hole.

The other thing they did was swapped the light switches. The one closes to the mudroom is on the left of the dbl box. The kitchen overhead light is on the right. Well the mudroom is to the right of the switches.

Sometimes you really have to wonder.

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Uh huh. I’ve never seen an open back box. Makes you wonder if it’s overloaded. If that “thing” is 32 cubic inches, then with four devices (switches) you only have room for 7 conductors plus the grounds (and that’s if there is not strap in the box).

I’ve seen shallow metal boxes back to back, but even then you usually use a double gang box with a single gang mud ring to make sure you have sufficient capacity.

Have fun, lol. :rofl:

It’s worse than I thought. To the right of the box is the wall stud for the door. To the left of the box is an HVAC vent. I don’t think I’ll be able to fit a standard 2 gangbox without cutting into the hvac. Why anyone would put a vent going into an inside linen closet it beyond me. Same spot on the wall down low by the feet is a vent going into the bathroom area where these switches are. I’m going to open up the vent and cap it just above. On the inside of the closet I’ll patch that part of the drywall. From there, I should be able to run a line extension putting in two 2gang boxes side by side. Needless to say, the wife unit is not happy about all this. However, she has been really enjoying all the added smarts to the house.

It may be worth trying to fit an old work box before going through all that.

I wonder if this would work… Mount a single red series dimmer in the box. Eliminating the second switch by connect the line to load. For the bulbs connected to the always on lead use smart bulbs (already in the overhead can lights). The control the on/off through the use of scenes. If I do this, I would only need to reverse the install whenever I plan to sell the house.

It wouldn’t be advisable, but as long as you know what you’ll need to do in order to be safe when changing out bulbs (knowing the socket is live) and you remember to swap it upon resell (but wouldn’t you be in the same predicament as now). It should work though…

I thought the dimmers/switches were about 1.3" deep so they should fit???

The problem isn’t the depth of the box… the problem is where the switch mounts. The width of the switch hits the top and bottom corners of the box. Checking the distance using a caliper, I would need to move the switch over by about 3.5mm to get it to fit correctly.

An electrical box with an open back is a fire hazard and should be replaced. The primary reason the NEC requires boxes is to contain a fire to keep it from spreading before burning itself out. I have had that happen twice in my house due to shoddy crimp connectors, and both times the damage was limited to only a single box.

An “open back electrical box” is most likely actually an extension ring, designed to mount on top of a metal box. That’s up to code, as long as it’s attached to a box with a solid back, so that the entire apparatus is fully enclosed.


I used this where I had limited space and I didn’t really want to open the wall to put in a deeper gang.

You will need to call around different suppliers as many are low/out of stock.

Its not as ideal as a flush wall install but in my case, was better than tearing out drywall, EMT conduit, and gangs.

That is exactly what @mbbush was referring to. That is a box extender, not a box. If you are in the US, the NEC requires that switches are to be installed in boxes, not extenders. As was pointed it, there are viable safety reasons for that requirment.

NEC 300.15

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I didn’t suggest not using a gang box. Clearly you want and need a gangbox for wiring and fire hazard reasons.

You can replace box #1 with as deep a box as you can get. Put the wires from box #2 in it…just pigtail them for more distance to where ever you locate box #2

I misunderstood. You’re suggesting using a box extender on top of the current installation and leave it proud above the sheetrock. That would certainly work to add box capacity. The only problem is the OP has a box extender on top of a box extender presently. He doesn’t have a box to add it to, presenting another issue.