Home Improvement Ideas DIY Home Electrical Tips & Guides How to Install an Electrical Box in a Finished Wall Follow these expert tips to install an electrical box into drywall or plaster without the need for wall studs or joists. By Caitlin Sole Caitlin Sole Caitlin Sole is the senior home editor at BHG. She is a writer and editor with nearly a decade of interior design expertise. She has vast experience with digital media, including SEO, photo shoot production, video production, eCommerce content, print collaboration, and custom sales content. Learn about BHG's Editorial Process Updated on June 2, 2022 Trending Videos Close this video player Project Overview Working Time: 15 minutes Total Time: 15 minutes Skill Level: Advanced Estimated Cost: $50 Not all fixtures need to be attached to a wall stud or joist. Lightweight fixtures can hold up on plaster or drywall if you have a remodel electrical box ($2, The Home Depot). Installing these handy boxes only takes about 15 minutes and they give you the freedom to decorate your space exactly how you want. Try your hand at this small electrical project using our step-by-step instructions below. Before you get started, plan the job carefully, as running cable through walls covered with drywall or plaster can be difficult. Remodel boxes (also called cut-in or old-work boxes) clamp to the drywall or plaster rather than attach to a framing member, making the work easier. However, they are only as strong as the wall surface to which they are clamped. If the drywall or plaster is damaged, cut a larger hole and install a box that attaches directly to a stud or joist. Select boxes that meet local codes. For a ceiling fan or a heavy light fixture, buy a fixture box that attaches to a fan-rated brace. Before cutting a hole, use a stud finder to make sure no joist or stud is in the way. Edmund Barr What You'll Need Equipment / Tools Stud finder Torpedo level Utility knife Screwdriver Hammer Drill Drywall saw (or rotary cutter or jigsaw) Cable clamps, if needed Materials Remodel boxes acceptable under local code Instructions Dave Toht Trace Box For your safety, turn off power before starting this project. If the box does not come with a cardboard template, hold its face against the wall, use a torpedo level to make sure it is straight, and trace it. With a utility knife cut the line deeply enough to cut through the drywall paper. Dave Toht Cut Hole Cut the hole with a drywall saw. Cut to the inside of the knife cut to prevent fraying the paper. Test to make sure the old-work box fits in the hole. Dave Toht Thread Cables Run cable through the hole. Strip 8 to 12 inches of sheathing and run the cable into the box. Whichever clamping method the box uses, ½-inch of sheathing should show inside the box. Tug to make sure the cable clamps tightly. Dave Toht Insert Box Push the box into the hole. If it fits tightly, do not force it or you may damage the drywall. If needed, use a utility knife to enlarge the hole in your wall. Dave Toht Secure Box to Wall This type of box has wings that extend outward when you start to drive the screw, then grasp the back of the drywall as the screw is tightened. Tighten the screw until you feel resistance and the box is firmly attached. Dave Toht What If the Wall Is Made with Plaster? Take your time cutting a lath-and-plaster wall when installing an electrical box. It's easy to damage the surrounding area. Most plaster is attached to ⅜-inch-thick wood lath, which cuts fairly easily if it does not vibrate. If it does vibrate as you saw, sections of plaster can loosen from the lath. It is difficult to make a neat hole in plaster and lath, so have patching plaster ($5, Walmart) on hand. If plaster is attached to metal lath, cut all the way through the plaster with a knife and then cut the metal lath with side cutters. Make several passes with a sharp knife. Drill starter holes at each corner and then cut with a jigsaw. Press the saw firmly against the wall to minimize lath vibration. Alternatively use a rotary cutter equipped with a plaster-cutting bit. Practice first because it is hard to control. Dave Toht Remodel-Box Options The round plastic ceiling box (left) has "wings" that rotate out and behind the wall surface. One metal box (center) has a flange that springs outward when the box is inserted; tightening a screw brings the flange forward. A variation on this has side clamps that move out and toward the front as screws are tightened. Yet another type (right) uses separate mounting brackets that slide in after the box is inserted and bend over the sides of the box to lock it in place.