Things You'll Need
Stud finder or hammer and finish nail
Retrofit electrical box
Drill or screwdriver
Remodeling work presents all kinds of challenges. One of the most common is a wall stud or ceiling joist not being right where you want it. But for simple wiring work, such as adding a light fixture, switch or outlet receptacle, the no-stud problem is easily solved. The answer is to use a "retrofit" electrical box, which is also called an old work or remodel box. This clever box has a flange, or lip, on the front edge that catches on the front of the drywall, while little flip-out tabs attached to screws pull the tabs tight to the backside of the drywall. Old work boxes also have integrated cable clamps, so you can secure the circuit cable before fitting the box into place.
Shut off the power to any electrical circuits in the project area by switching off the appropriate breaker at the home's service panel or breaker box. Determine the approximate location for the new box. Check for studs or other framing in the area using a stud finder (or do it the old fashioned way, with a hammer and finish nail). Mark any stud near the box location.
Place the retrofit box face down against the drywall, precisely where you plan to install it. The box's flange should be at least 1 inch away from a stud. Trace around the outside of the flange with a pencil; this is merely a reference line to prevent you from cutting too large of a hole.
Flip the box over and place the back side against the wall so it's centered within the reference line. Trace around the box body with the pencil; this is your cutting line. Cut out the drywall along the cutting line, using a drywall saw or keyhole saw. Work slowly, and stop to investigate if the saw meets any obstacles inside the wall cavity.
Fish the appropriate circuit cable through the wall cavity and out through the new hole. Feed the cable through the clamp in the back of the box. Fit the box into the hole, and hold the flange tight against the drywall face. Tighten the screw for each tab, using a drill or screwdriver. Tighten the screws snugly, but be careful not to over-tighten and damage the tab or break through any fragile drywall edges. Complete the fixture wiring and installation, as appropriate.
Contact your city’s building department to learn about installation requirements for new wiring. Retrofit boxes are designed for lightweight fixtures and should not be used to support heavy fixtures and devices, which require a metal electrical box mounted directly to wall or ceiling framing or suitable blocking or bracing.