I am in the process of wiring my addition. I am wondering what it the most commonly used outlet and switch boxes used by the pros when wiring 2 x 4 stud walls. The plastic boxes are larger and give you more room for the wires, but leave little room for error when drywalling. Metal boxes seem to look more professional but do not fit flat on the studs when nailing. One end sits out about 1/8" because of the interlocking flanges on the box. Do I need to find a different metal box for studs, or do you need to drill a recess hole for the flange (1/4" or so)? Also, when ganging 2 metal boxes together how do you fasten the box to the studs? A #16 nail is not long enough to go through 2 boxes. Thanks
COMMUNITY FORUM
- Forum >
- Electrical & Lighting >
- metal or plastic boxes?
First, there is no "preferred way." Pros use both. Metal is stronger, can provide a grounding point for any devices connected to it, and is necessary if you are using metal conduit. Metal can also conduct electricity, though, and create a short by coming into contact with an inadvertantly exposed wire.
Plastic does not create shorts when in contact with inadvertantly exposed wire. (You should take care to not allow wires to become inadvertantly exposed inside the box, anyway, but it provides "belt and suspenders" protection, just in case.) Plastic is often easier to work with, and you should independently ground everything to ground wires, anyway, not just the boxes attached to ground wires.
Metal boxes can be just as large if not larger than plastic. You are just judging the dimensions of the boxes in stock at your local store. I use deep metal boxes when I need MORE space.
Metal boxes (even gangable ones) come both with and without attached brackets for attachment to the studs.
You should not secure a box by nailing THROUGH the box from the outside edge. Secure the edge that is flush with the stud from inside the box, or (better yet) with a bracket that is attached/welded to the box. I use screws to secure boxes because you get finer control over where they end up. Use an extended screwdriver-bit (6 inches or longer) to be able to screw the screw outwards from inside the box.
The room for error when using plastic or metal boxes is exactly the same. A 1/8" gap is allowed between the sides of the box & the drywall, coincedentally, this is the exact gap left if you use a roto-zip tool for cutting out the hole.
Personally, I prefer the plastic boxes from a cost standpoint and the fact that there is more of the box pressed against the stud than a metal box with a 1" wide nailing flange.
Tom
