Running electrical wire through closed walls is a project that few do-it-yourselfers enjoy. After all, the true focus of the task is the electrical wiring and the benefits it brings: extra outlets, new lights, power for an additional appliance. Cutting into drywall, patching it, and doing so efficiently 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 annoying side project with greater ease. Plus, you'll keep your house cleaner.
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.
Accurately Pinpoint the Wire
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 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 it run diagonally or at other angles.
- To find the exact location, you will need to purchase an expensive scanner that uses radar technology, such as the Bosch D-Tect 150 Wall and Floor Scanner. Use this only if you are a professional and expect to be locating many hidden wires. A conventional stud finder will not locate wires.
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.
Cut the Smallest Size Possible
To access the electrical wire, you will not be removing 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 about 4 inches.
Perfect Dimensions Not Necessary
It is not necessary to create perfect squares, rectangles, or circles 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.
Use an Effective Cutting Tool
Manual jabsaws are the tool of choice 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 half-inch 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, if you need.
Keep It Clean
Erect a dust barrier such as a Zip-Wall when cutting the drywall with any power tool. Lay down a dropcloth under the cutting area that can be carefully rolled up and discarded.
Patch the Cut Drywall
After installing the electrical wire and testing the devices, patch the drywall. You have a few patching techniques at your disposal:
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.