

In these cases, you can't use those snap-apart spacers.
#Plastic plaster ring code
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). 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. 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. The code allows for boxes to be up to 1/4" back into a drywall wall (i.e. 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. If you're really concerned, make a simple jig with some plywood that will help you to position the boxes. Use the ruler to span across TWO studs, then use that as a guide for the boxes. 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. 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). I'd say the reality is that the depth of the box isn't really super critical if you're using drywall.
