Most electrical wires in homes are hidden behind drywall. While this helps to hide unsightly wires, it makes it more difficult to work with those wires. Running electrical wire through closed walls is a project that few do-it-yourselfers enjoy. The true focus of the task should be the electrical wiring, not rough carpentry and demolition work. Cutting into drywall is little more than collateral damage that needs to be minimized.
Understanding the nature of drywall, studs, and electrical wire and how they interact will help you push through this side project with greater ease. As an added benefit, you will keep your house cleaner.
Basics of Cutting Drywall For Electrical Wires
Finding existing wire behind drywall is more like detective work than an exact science. To find the exact location of wire, you would need to purchase an expensive scanner that uses radar technology. Use this only if you are a professional and expect to locate hidden wires on a regular basis. A conventional stud finder will not locate wires but it will help you locate studs, and this is valuable information that can help you find the wire.
To access the electrical wire, it is inefficient and time-consuming to remove entire sheets of drywall. Rather, you want to remove the smallest section of drywall possible, while maintaining a large enough opening to insert a drill or your hands. Usually, this space is about 4 inches wide.
Manual jabsaws are good, inexpensive tools for quickly cutting an occasional hole in drywall. But electrical wire runs can often be so long that manual cutting is too much work.
For cutting across an entire room, hallway, or other long distances, snap two chalk lines 4 inches apart. 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). 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.
Codes and Regulations
Most electrical work will require an electrical permit. Running new wires is, in most communities, a permitted project.
Walls can contain electrical wires, plumbing pipes, insulation, cross-bracing, and construction debris. Wear eye, hearing, and breathing protection before cutting into the wall. Shut off all power to that area, even if you think that the wall has no wires.
- Working Time: 30 minutes per 8 linear feet
- Total Time: 8 to 12 hours
- Skill Level: Expert
- Material Cost: $10 to $30
Tools and Materials
- Drywall for patching
- Paper drywall tape
- Drywall compound
- Voltage tester
- Circular saw
- Chalk line
Turn Off the Power
Whenever working with cutting tools, closed spaces, and electrical wire, turn off the electrical circuit that supplies power to that area. This is vitally important because the process of locating the electrical wire can often be hit-or-miss.
Set up the Dust Barrier
Erect a dust barrier such as plastic sheeting when cutting the drywall with any power tool. Lay down a dropcloth under the cutting area that can be carefully rolled up and discarded.
Accurately Pinpoint the Wire (Optional)
Where is your electrical wire located? A few tools and methods will help you find either the exact or basic location of wires running through your walls.
- Between wall outlets, the electrical wire will generally run horizontally, about 12 inches high.
- Wiring usually will extend vertically up or down from light switches.
- Between a light switch and a ceiling light, first imagine the shortest pathway behind the walls and ceiling. Then, take into account the direction that the ceiling joists run. Wiring usually will run parallel or perpendicular to the joists. Rarely will wire run diagonally or at other angles.
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. 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 to 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. Use fishing tape to direct the wire blindly through the closed-up cavity into the hole 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. Also, cut off any loose wires from the end of the cable to form as sharp an end as possible.
It is not necessary to create pin-point exact shapes when cutting into drywall for wire runs. So, don't stress over making perfect shapes. Since electrical cables run in lines, it is helpful to make long, narrow cuts.
Patch the Cut Drywall
After installing the electrical wire and testing the devices, patch the drywall. You have two patching techniques at your disposal:
- Bevel-Cut Patch: One way of patching drywall involves beveling the hole in the wall to a 45-degree angle, then beveling the patch piece at a reverse 45-degree angle. This is similar to cutting out the top of a pumpkin so that the top does not fall through. 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.
- Patch With Backers: 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. 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.
For both methods, conclude by filling with drywall compound, leaving to thoroughly dry, then sanding.