Build my own cabin - DIY projects

Should I use Plastic or Metal Electrical Boxes

The NEC permits use of plastic boxes with non-metallic cable only. This includes Romex or NM wiring.  You should not use metal-sheathed or "BX" wiring with plastic electrical boxes. The reasoning is simple -- with armored cable, the box itself provides ground conductor continuity. Plastic boxes don't use metal cable clamps and do not provide the required grounding path.


 The advantage of plastic boxes is comparatively minor even for non-metallic sheathed cable -- you can avoid making one ground connection and they sometimes cost a little less. On the other hand, plastic boxes are more vulnerable to impacts. For exposed or shop wiring, metal boxes are probably better. Metal receptacle covers must be grounded, even on plastic boxes. This may be achieved by use of a switch with ground connection.

Metal electrical boxes are primarily used with metal-sheathed or "BX" wiring.  However, they can also be used with Romex or NM wiring if desired.

Most new residential electrical systems use Romex and plastic boxes.  Most do-it-yourselfers will find this combination easier to work with as well.  Plastic boxes are lighter, some already have nails attached, and holes are easier to knock out than metal boxes.


Wiring a House