Most electrical wires in homes are hidden behind drywall to protect and hide unsightly wire bundles. Sometimes it becomes necessary to pull wires through walls if, for example, you are adding an outlet or switch to a space. Running electrical wire through closed walls is a tedious project that few do-it-yourselfers enjoy. It is inefficient and time-consuming to remove entire sheets of drywall just to access wire. Rather, you want to remove the smallest section of drywall possible, while maintaining a large enough opening to insert tools and hands. However, sometimes you'll need to cut drywall across an entire room to adequately run wires.
Handling the electrical wiring takes priority over the aesthetics of cutting into drywall, but it helps to know the best ways to minimize the damage you'll inevitably inflict on the walls to run the wire. Understanding the nature of drywall, studs, and electrical wire and how they interact lets you push through this side project with greater ease. It's also important to note that most electrical work, including running new wires, requires an electrical permit in most communities. If you are uncomfortable tackling DIY electrical wiring projects, it is always best to hire an electrician.
Equipment / Tools
- Voltage tester
- Stud finder
- Drywall jab saw
- Chalk line
- Circular saw
- Multi-tool (optional)
- Fish tape
- Hot glue
- Plastic sheeting/drop cloth
- Painter's tape or electrical tape
- Drywall for patching
- Paper drywall tape
- Drywall compound tape
- Backer supports
- Medium-grit sandpaper
- Fine sanding sponge (optional)
Preparing for Cuts
Walls can contain electrical wires, plumbing pipes, insulation, cross-bracing, and construction debris. First and foremost before cutting, protect yourself first by wearing eye, hearing, and breathing protection before cutting into the wall.
Turn off the Power
Whenever working with cutting tools, closed spaces, and electrical wire, the first rule is always to turn off the electrical circuit that supplies power to that area. Shut off all power to that area of your home, even if you think that the wall has no wires. This is vitally important because the process of locating the electrical wire can often be hit-or-miss.
Protect Room From Drywall Dust
Erect a dust barrier from floor to ceiling using plastic sheeting and painter's tape to reduce drywall dust when cutting. Lay down a drop cloth under the cutting area that will be rolled up and discarded after the project is completed.
Pinpoint the Wire
Construction professionals use scanners with radar technology to locate hidden wires. A conventional stud finder will not locate wires, but it will help you locate studs, which is valuable information that can help you find the wire without the need for a scanner. Some modern stud finders now do have the ability to alert when wiring is detected, though.
If using a stud finder isn't an option, know that most outlets and some switches will usually have 2 or more sets of wires running to them. It can be helpful to look into the box and determine where the wires enter the box: at the top, bottom, or occasionally the sides. This will give you an idea as to where to start tracing wires so as to not accidentally cut into them.
Here are a few other tricks to help you locate wires running through your walls.
- Between wall outlets, the electrical wire will generally run horizontally, about 12 inches high from the floor.
- Wiring usually will extend vertically up or down from light switches.
- Wiring usually runs parallel or perpendicular to the joists.
- Rarely will wire run diagonally or at other angles.
Small Runs: Cut Between Alternating Studs
To run electrical wire horizontally in walls, it is helpful to know that most wall studs run either 16 inches or 24 inches on-center.
Since electrical cables run in lines, it is helpful to make long, narrow cuts with a manual jab saw. But electrical wire often runs through long walls which requires more than manual cuts.
Locate and mark with painter's tape or electrical tape the location of every stud, as you will be cutting between studs.
For interior walls or any walls that do not contain insulation, it is possible to cut only between alternating studs cavities. This halves the number of holes you need to make in the wall.
Create access holes in the drywall that are roughly 4 inches by 4 inches, enough so you can insert your hands and a drill to cut a hole in the studs for fishing through the wire.
Try to drill close to the center of studs or joists—this should affect the integrity of the wall much less. Also, at these spots, the wire should be deep enough that the drywall screws will not puncture it. If it is necessary to drill close to the edge, use metal protection plates to cover each stud drilled to protect the wires.
Use fishing tape to direct the wire blindly through the closed-up cavity into the bored holes you've made in the stud.
Often it is possible to blindly hit the hole with the wire itself. To do this, the hole in the stud must be generously sized.
Cut off any loose wires from the end of the cable to form as sharp an end as possible.
Larger Runs: Cutting Entire Walls
When you have much larger runs to handle, you will inevitably need to cut across the entire wall, even over the studs. While messy, this is the fastest method of cutting out long, narrow sections of drywall.
A multi-tool fitted with a wood blade is a cleaner, slower method. Plunge cut straight into the drywall, even atop studs.
To cut across an entire room, hallway, or other long distances, snap two chalk lines 4 inches apart.
Cut Wall for Access
Fit a cordless circular saw with an old, used blade and set the depth to about 5/8-inch (for 1/2-inch thick drywall).
Final Step: Patch the Drywall
After installing the electrical wire and testing circuits and devices, shut off the electric again so you can close up the drywall using patches with backers.
For each hole, create a patch piece so that it is the size of the hole in the wall. Do not cut at a bevel; cut straight in at a 90-degree angle.
Another way of patching drywall is the bevel cut patch method: beveling the hole in the wall to a 45-degree angle, then beveling the patch piece at a reverse 45-degree angle. Before placing the patch piece, scuff away some of the gypsum from the cut sides to cause the patch to recess into the wall by about 1/16 inch.
Glue Backer Supports
Glue backer supports (using wood paint stirring sticks) inside the hole with hot glue. Strip off the back paper from the patch piece. This will cause the patch piece to recess into the wall about 1/16 inch.
Compound the Patches
Fill patches with drywall compound. Leave to thoroughly dry. Smooth with medium-grit sandpaper around the patch. Finish smoothing drywall with fine sanding sponge.