But sometimes, it’s not always possible to find a suitable mounting point against the studs. What about between the studs? Using old-work electrical boxes is one way to hover the boxes between studs. Old-work boxes attach directly to the drywall, not to the studs. After cutting a rectangular hole in the drywall, you insert the electrical box in the hole. Then, with either a manual Phillips screwdriver or a cordless drill/driver, you turn the two screws clockwise. Turning the screws also turns the two plastic wings behind the drywall, forcing the box against the drywall. While it’s not as strong as a stud-mounted box and sometimes the wings will break off, often it’s the only option when you want the box to be between studs.
Wall Switches
It is standard practice for wall switches to be installed about 48 inches above the floor. But this distance can range from 43 to 53 inches, depending on your preference. For spaces used by people with accessibility issues requiring a wheelchair, for example, lower switch heights might be practical.
Outlet Boxes Over Flooring
The common practice for receptacle outlet boxes is to install them so the bottom edge is between 12 and 16 inches above the floor. This distance, too, can be adjusted for special circumstances.
Outlet Boxes Over Countertops
For switches and outlets above countertops, install them so the bottoms are about 4 inches above the countertop surface. When you install an electrical box, make sure it is flush with the surface of this drywall strip; this will ensure the boxes are at the proper depth when the walls are finished. Most residential drywall is 1/2- or 3/8-inch thick, so keep a handful of drywall strips of this thickness on hand to facilitate electrical box installation. If you are using a different wall thickness (such as 5/8-inch thick, required for some firewalls) make sure the reference strips match that thickness. Begin by slightly pushing out the nails on the box by hand, so that when you place the box against the stud, the tips of the nails lightly pierce the wood. This helps hold the box in place during those first couple crucial strikes of the hammer as you drive the mounting nails into the stud. Some electricians stop just short of driving the mounting nails completely into the studs. This allows the box to be easily removed should the layout need to be changed before the NM cable installation. But certain cords are thicker and heavier, placing a dangerous amount of strain on the outlet and the box. Dryer cords are attached to 240 V outlets, and while the cords aren’t frequently moved, they do place a heavy, constant burden on the outlet box. Similarly, a 240 V, 40 A Level 2 electric vehicle charging station is commonly attached to a NEMA 14-50 outlet. The less expensive Level 2 EV chargers have no wall station, so they plug directly into the outlet. This action places a great deal of strain on the outlet, day in and day out. Chargers that have permanent wall stations are less likely to add strain to the outlet—more like permanently attached dryer cords. With any type of larger, 240 V outlet, it’s often best to use a metal box, especially for cords that are frequently removed and replaced.
