Currently have a ganged, steel electrical box with two switches, and
need to add a third. Needless to say it's in old work--finished
drywall. Thought about making stud-to-stud cuts above and below
existing boxes, then adding the third section. Then I thought I'd
better ask here first.
Is there a way to do this without so much drywall cutting?
It's a little tricky, but doable. If you've got 2x3 gem boxes, the end plate
is held on by a screw at the top of the box. If you cut the sheetrock for
the additional gang, then pop a slim screwdriver through the sheetrock at a
steep angle above the retaining screw, unscrew it and remove the end plate.
Next install the additional gang which will have both top and bottom screws
which you can tighten through the existing top hole and by making another
screwdriver hole at the bottom. This way you only have two small holes to
If you have enough room in the existing box, you can convert one of
your existing single gang switch to a duplex single gang switch,
leaving you a spot for your new switch. The only thing you would have
to do at that point is run a new wire for your switch to the box.
What I have done before is use a three position remodel box, cutout the
extra drywall needed for the newer bigger box, carefully remove the old
steel box off the stud through the bigger opening, feeding the existing
Install existing wiring with new wiring into new box and install.
The only catch is really need to have a good tight fit and solid drywall
where the back flaps hold to the drywall for the type of box that has the
screws in the opposite corners that have the flaps on the back that twist
into place and tighten down to hold the box in place.
That's an awful lot of work to add another gang section.
Would you consider using a duplex toggle ( 2 switches on one strap)?
You can get a cover plate which will "marry" a single toggle
to a duplex. Even do it in Decora style.
Is this metal box connected via EMT? If not (and maybe if Yes) you could
always buy a 3 gang plastic box designed for old work. I just replaced a
two switch box with a 3 gang and was able to mount one side to the stud and
use the "ears" to tighten it against the drywall. It's pretty solid. Now
I was running NM. If you are running conduit etc... then all bets are off
(although I think you can use a plastic box on EMT providing you provide a
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