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I have an old 3-gang metal junction box that is nailed to a stud on one side, via the "new work" straps above and below it. No other part of it is fixed to anything, and it has become a little loose over the years (or perhaps it always was) so the opposite side rocks in and out of the wall slightly and, at rest, is a bit recessed into the wall.

The plaster wall on which it's mounted is not in the best shape, and not very straight, so the devices' plaster ears don't do their job very well.

Is there a reasonable approach to improving the strength and alignment of this box other than reinstalling it? The objective is to provide a better foundation for devices and wall plates so they don't move and flex while in use, but without breaking open the wall to install a new box (IE avoid plaster and paint repairs).

The relevance of "3 gangs" is the degree of movement in the side furthest from the mounting stud. I have this problem is smaller boxes too, to a lesser degree.

See this question for the consequences of not repairing this: The electrical devices installed in the box are easily damaged by rough treatment.

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  • Is the wire coming into the box regular NM wire held by a clamp within the box, or do you have conduit or armored cable?
    – Machavity
    Commented Apr 22, 2022 at 19:13
  • Armored cable. Nicely terminated and clamped.
    – jay613
    Commented Apr 22, 2022 at 19:21
  • Use the stamped metal clamp/clip (Madison straps?) to secure the far end of the box to the inside of the wall. The cover plate will secure it to the outside of the wall. youtu.be/-pFnaQFAu40 Commented Apr 23, 2022 at 2:49
  • @JimStewart a Madison strap (that you only just introduced me to, thanks) and a metal cover plate are a good idea for the "far end" (opposite the stud) of the new work box. See the linked question where I had switches badly damaged in such a box. My cover plate was soft plastic and, being the only thing preventing the box from moving into the wall when pushed or banged, this was an important factor in all the damage noted in that question.
    – jay613
    Commented Apr 24, 2022 at 14:16

3 Answers 3

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I routinely bolster such boxes in several ways:

  • Run screws into the stud. If there aren't holes, I make some. One front and one rear usually does well.
  • Drop shims behind with some construction adhesive or silicone for stability.
  • Use steel strapping to hook the box edge on top and bottom. Fold an L or V in one end and hook it behind the plaster or wallboard. Pull it snug and bend it around the box. This should do a reasonably good job of keeping the box forward.
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I would drill holes in the side of the box that is flush with the stud (if there aren't holes already). Never put holes on knockouts (not least, they won't hold). At least 2 near the front and 1 near the back.

Then I would use 1-1/4" deck screws (pretty much my go-to for all sorts of stuff lol) with TORX heads, and use those through the holes into the stud. (pre-drilling if warranted).

I like the TORX heads because they're easier to drive with a side ratchet screwdriver that has a bit holder. Don't even try it with Philips, good grief.

The original installer used nails, and those can be pried out by undue force. Deck screws don't pry out (at least if they do, you've got bigger problems).

You know, those modular metal boxes that stack up to make multiple gangs... they're not THAT sturdy. They can start coming apart on you. They just aren't made for high impact service. That would require special bracketry, probably a horizontal stud brace top and bottom and attach the box to those bottom and top.

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Combining suggestions from answers above (isherwood and Harper), from a comment (Jim Stewart) and from another comment from Harper in the and answer from Machavity both in the linked question:

  • Improve the nailed side by drilling through the side of the box (if necessary) and driving screws into the stud , one near the front and one near the back of the box. Torx head deck screws and a right angle ratchet driver are effective.
  • Improve the opposite side by using a Madison Strap and a high quality Mid size metal wall plate. Together, these metal parts will secure the box effectively to the plaster even if the edges of the plaster are frayed or the hole is a little too large. To improve aesthetics the wall plate can be spray painted to match the switches and sockets and other nearby wall plates.
  • Use high quality switches and sockets with yokes that don't flex too much under pressure, and use spacers if necessary, front and/or back of their mounting screws, so they are held tight against the box and the wall plate. Without this step the other steps will not prevent them from moving under pressure from users.

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