Metal framing has become increasingly popular among residential and light commercial contractors, and there are differences in how the electric outlet and switch boxes are attached. Electrical boxes help prevent short circuits that can lead to fires, so it is vital that they are anchored correctly. This article discusses the many types of electrical boxes used in residential and commercial construction, what they are made of, and how to attach them to a metal stud.
Different Types of Electrical Boxes
All electrical boxes must be installed in accordance with the National Electrical Code (NEC) and local building codes. They must meet the requirements of the code, which states that they should be covered with suitable box covers. The boxes can’t be wallpapered, paneled, or covered over in any other way, and need to provide sufficient room for the conductors within it.
There are several types of boxes, but for the purpose of this article, we’ll focus on the three most common types: standard electrical boxes, remodel electrical boxes, and GFCI electrical boxes.
- Standard electrical boxes – A standard rectangular shape is the most common electrical box. It houses a single electrical switch or outlet and comes in metal or nonmetallic units. When used outdoors, these boxes protect wiring from the elements with gaskets, sealed seams, and watertight covers.
- Remodel electrical boxes – Also known as old-work boxes, these are put up after drywall has been put in place to add a switch or outlet to your room. These are often held in place with tabs that draw the box tight with the drywall without the need for screws.
- GFCI electrical boxes – The GFCI outlet is different, however, the box that houses it is the same as a standard electrical box.
What Materials are Used to Make Electrical Boxes?
Electrical boxes are made from various materials, including plastic, metal, and composites. The most common type is the standard box, which is made from plastic or a composite material. Plastic boxes are lightweight, durable, and easy to install, but more fragile than metal. Composites are great for situations where metal is not desired, but more strength than plastic is needed. Metal boxes are designed to be used with steel and wood framing. GFCI electrical boxes are made from plastic or metal and are used in wet areas, such as bathrooms and kitchens.
Choosing the Right Electrical Box for Metal Framing
There are several types of electrical boxes and each one is designed for a specific purpose. The most common type is the flush mount electrical box. This type of box is used to install electrical devices that will be flush with the wall. These come in single gang, double gang, etc., to accommodate multiple switches or outlets.
The flush mount boxes for wood framing differ from those designed for use in steel framing. Some steel framing electrical boxes have metal tabs that fit into the slots on the metal studs. Others have an attached tab that allows the box to be screwed to the metal stud. Still, other options contain tabs that bend around the front and rear of the metal stud to hold it before attaching it with a screw.
Can I Use Plastic Boxes on Metal Studs?
You should check your local code enforcement first, but generally speaking, plastic boxes can be used on metal studs. However, they cannot be grounded in the same fashion as a metal box. To ground devices like switches and outlets, you must run the equipment-grounding conductor into the enclosure. Connect the ground wire directly from your Romex to the green screw on the switch or outlet. This will ensure the system continues to ground throughout the leg.
Attaching the Electrical Box to Metal Framing
- Place the electrical box on top of the metal stud and measure up from the floor with the tape measure. Make a mark on the inside face of the metal stud with a permanent marker at the bottom height required to install your electrical box.
- Most boxes will have a stop or tab that keeps the front of the box either ½” or ⅝” out from the stud to account for the depth of the drywall.
- Secure the box to the stud with an electric drill using ¾” No. 6 self-tapping metal screws. The box will either have side tabs with pre-drilled holes for this purpose, or longer straps intended to wrap around the stud and attach through the sides.