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Community and Q&A

Efficient technique for setting depth of plastic electrical outlet boxes on beveled studs

etting | Posted in General Questions on
I’m about to start wiring the house I’m building, and I’ve discovered that the two little depth-setting nubs on my Carlon plastic outlet (receptacle) boxes seem to be intended for studs with square edges.  Carlon’s instructions say to press the nubs against the edge of the stud, but with the beveled edges on all of my studs, the box ends up protruding only 1/4″ beyond the face of the stud, which makes it impossible to screw the outlet all the way against the box and still have the wall plate fit onto the outlet after 1/2″ drywall is installed.  A recess of 1/4″ is supposedly allowed by code for a non-combustible wall covering, but it would require fussing with how far to screw each outlet into the box, and the outlet would be more wobbly than if it were screwed all the way down.  
The best solution I’ve devised is to use a credit card to extend the plane of the stud face over its beveled edge and then set the little nubs against the credit card, but I have to do that quite gently, or the nubs bend the edge of the credit card down over the bevel.  It’s much easier to nail the box in place if you can press it firmly against something.  If I can find a slightly thicker steel plate that won’t bend, perhaps a wide putty knife, it may work well, but only if it’s not so thick that the box will protrude past the drywall.  I know it’s much better for the box to be a little too recessed than to protrude too far.
I’ve spent a couple of hours reading articles and watching videos on the best way to install these plastic boxes, and the only advice other than to press the nubs against the studs is to use a scrap of drywall to measure the box depth, but that seems fussy, subjective because you still need some recess, very difficult to maintain the measurement while you’re nailing the box in, and prone to ending up with some protruding boxes.
Is there a better way to nail these plastic boxes at the right depth?

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  1. andy_ | | #1

    The reality is that the guys who do this day in and day out just bang them on to the right depth from experience or they just don't fuss over such a small detail.
    If it really bugs you, then the scrap method is the way to go. If you really really want them all exactly perfect, then you can make a small jig to hold them in place.

    1. etting | | #4

      I can believe that guys who do this all day get it mostly or entirely right by eye, but I disagree that it's a small, fussy detail. Wobbly outlets or wall plates that don't make contact with the outlet surfaces would be flaws well worth avoiding to me, at least.

  2. Expert Member
    BILL WICHERS | | #2

    I'd say the reality is that the depth of the box isn't really super critical if you're using drywall. You can get spacers to shim the outlet out to the right level if you can't use the plaster ears on the device itself to clamp against the drywall (this doesn't always give a tight mounting though). Metal faceplates help too.

    If you want to keep things consistant, I would use a steel ruler, which will typically be around 1/16" thick or a little thicker, and will be pretty stiff material. Use the ruler to span across TWO studs, then use that as a guide for the boxes. If you're really concerned, make a simple jig with some plywood that will help you to position the boxes.

    I personally wouldn't worry about it too much, just use the little snap-apart spacers if you need an extra 1/16" to 1/8" or so. The code allows for boxes to be up to 1/4" back into a drywall wall (i.e. up to 1/4" of exposed drywall between the edge of the box and the finished surface of the wall), but try to keep that distance as small as you can for secure device mountings. If you have more than a 1/4" recessed box, you need to use one of the box extenders that looks like a plastic shroud.

    Note that if you are working with combustible finished wall materials like shiplap or wood paneling, the code requires the box to be flush with the finished surface or slightly protruding from it (which will complicate device mounting, you don't want your box edges proud of the wall surface since the faceplates won't sit flush). In these cases, you can't use those snap-apart spacers.

    Note that if you're using metal 4" square boxes (or some plastic types), you have a selection of different depth mud rings you can use, so the box only needs to be parallel to the wall surface, the depth is very non-critical -- just use whatever depth mud ring you need to bring the device mounting location up to flush or very close to flush with the finished wall surface. I like to use metal boxes and mud rings in complicated situations where the boxes will be deeply recessed in the wall (this happens sometimes in remodels), or use one of the adjustable depth plastic boxes that mounts to the stud with a metal plate and has a screw that allows you to adjust the depth of the box in the wall -- even after drywall is up.


    1. etting | | #3

      Thank you, Bill, for such a thorough reply. I probably should have included a photo of the type of box I'm talking about. In the attached, the nubs are on the front left. This design won't allow me to span two studs with a steel ruler to press the nubs against, but a steel ruler should work well against one stud. I'm surprised none of the articles or videos I saw even acknowledge this problem, let alone propose a solution. I'll be interested if anyone has devised other solutions.

      1. Expert Member
        BILL WICHERS | | #10

        I'm not a fan of those style boxes since they always seem to be a little bit loose after installation. As Rebturtle mentiones below though, you can "adjust" these boxes a little by bending, just be careful not to overdo it and break any of the plastic nail supports.

        I much prefer the fiberglass "hard boxes" if I have to use nail-on boxes. The hard boxes are more secure, but you have to be more careful when isntalling them since they will crunch/break more easily than the blue plastic boxes which tend to just bend and deform. Even better are the boxes that mount with a bracket that allows adjustments.

        I think the reason that the installation of these boxes isn't discussed much is that no one really tries to install these boxes with very much precision. Most of the installation is just eyeballed, and there is a lot of "good enough" installs. I find the boxes are often not quite square, not quite parallel to the studs (one nail is a difference distance back from the face of the stud than the other), or the boxes are just too loose. The boxes that mount with brackets solve most of these issues, but the tradeoff is a higher cost per box.


        1. etting | | #11

          From the experimenting I've done, I can see how any but the most skilled may end up installing these somewhat crooked or too deep or shallow. When I pressed the nubs against the stud, I found the box easy to nail in straight and tight, but when I tried other techniques, it was quite difficult. I think pressing the nubs against a steel ruler or something similar will be my best solution. The design of these boxes would be improved by making the nubs taller (not longer) so that they would reach past the beveled edges on most studs. This might cause some difficulty if one were installing drywall thinner than 1/2", but that has to be a very small percentage of installations.

          I'll take some comfort in the cost I'm saving by taking the time required to install these least-expensive boxes properly.

    2. Expert Member
      NICK KEENAN | | #6

      Bill -- related question:

      You know how there are metal box supports you can slip behind the drywall and bend into place to support a metal box? Is there anything similar for plastic to firm up a wobbly box? I assume you can't use the metal ones on a plastic box because the box isn't grounded.

      Or do you just have to cut out the box and put in an old work box?

      1. Expert Member
        BILL WICHERS | | #9

        I'm not aware of any stabilizers that can be retrofit onto a loose plastic box. I agree with you that the metal supports probably aren't a good idea, since they could potentially come into contact with energized things inside the box and then be a hazard without a ground connection.

        I'm a big fan of the Madison "Smart boxes" to fix problems like this. Here is a link:
        I've found these to be very solid and they mount very securely, and you don't need a hole bigger than the box to install them so there is no drywall patching to do. If you're careful, you can cut out one of the nail-on plastic boxes from the front of the wall, pull out the wires, then replace everything with one of those Smart boxes and install it from the front of the wall. Bosch makes an awesome extender rod (in 6" and 12" lengths) for the hexagonal 1/4" screwdriver bits that makes these boxes very easy to install -- I hightly recommend these extensions.

        If you go with a plastic old work box, the downside is that the faceplate might not sit flush since the box will be proud of the finished wall surface about 1/16" or so.


  3. Patrick_OSullivan | | #5

    As has been mentioned, the folks who use those cheap boxes are not very discerning, and they just get banged on.

    I mostly use these:

    I install them with GRK cabinet screws. The adjustability is particularly nice in walls where the finished depth is variable, e.g. tiled walls. When I run out of these boxes (like right now, and they are very backordered currently, presumably due to plastic resin shortages), I switch to 4" metal boxes with mud rings. The nail on plastic boxes are my last resort.

  4. rebturtle | | #7

    Okay, I just stumbled across this tonight while looking for something else, but let me please chime in. As an electrician of 20+ years, yes, the depth IS very important. As others have said, the pros generally get a feel for it, but since it's literally the first task you're given as a new apprentice, it's still often done wrong.

    If you use the built-in tabs, as you noticed they will rest too far back because of the bevel on the stud. They will ALSO rest too far back because those spacers measure 3/8", not 1/2" or 5/8" like typical drywall. As stated, the NEC allows up to 1/4" gap from the edge of the box to the face of noncombustible materials (drywall is considered noncombustible for this rating). For any other "combustible" material, that clearance is ZERO! This is important because it's all about fire protection. You are preventing any kind of future electrical fire from jumping the gap and entering the wall cavity where it can travel up or to other rooms (remember that the NEC is published by the National Fire Protection Agency. Almost every rule is intended to reduce either the risk of electrocution or fire in some manner. The NEC isn't concerned with efficiency or aesthetics.)

    Now if you find after drywall that the boxes ended up recessed more than 1/4", you can buy what are called "box extenders," -what we colloquially call "spark-guards." They are basically thin sleeves with a pair of longer screws used to bridge that gap up to about an inch if needed. I prefer the plastic ones because I can trim them with tin snips if needed and don't have to wrap the devices with electrical tape. The stackable/foldable cat-a-pillar device stabilizers are amazing and I recommend them highly if needed, but they do not address a fire hazard.

    With all of that said, the solution is deceptively simple. Gather up a small cutoff piece of drywall, plywood, lumber, etc that measures the same as your expected finish drywall and hold it against the stud. Bring the box flush to it. Since this is kind of a three-handed operation and you only have two, use one hand to grip the box against the stud in the right location, then drop the block and use that hand to pick up your hammer. Give the nails just enough taps to either hold the box in place or indent the wood, then you can readjust into a more comfortable position if needed and continue.

    As for the "feel-of-it" experience, for me it is a matter of placing one hand in the box, four fingers pressing it against the stud, while my thumb feels for the proper amount of gap between the nub and the stud. Since I am right-handed, that has generated the awkward reach-across-myself-with-the-hammer-and-then-readjust method when nailing to the right side of a stud. When I was learning, everyone on our crew bought 16" hammers, too. You walk up to the stud, set your hammer upside down on the floor in front of it, and align the top of the box with the handle of your hammer. Then it is conveniently in front of you to pick up and nail the box in with. Every single receptacle was at the same height without ever having to measure or even mark the stud.

    The blue boxes are very forgiving. Once on the stud, you can give them light taps with the hammer on the face, edges, or corners to straighten them. If you find that a box is sticking too far out of the wall AFTER drywall, here's the pro tip - drive a 6-32 screw (not a drywall screw) most of the way into the mounting hole. Place a (Phillips, hopefully) screwdriver on the head of the screw, and tap the screwdriver lightly with a hammer or (if you're an electrician) your lineman pliers. The mounting nails will bend slightly and you can probably get up to 1/4" of forgiveness out of it that way without damaging the face of the box or the drywall around it.

    So yes, it is all important, but as long as you understand the mechanics of why, you don't need to overthink it too much. Best of luck on your project

    1. etting | | #8

      Great tips, Rebturtle; thank you!

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