A decent stud finder is a must-have for every wire-fishing job, but don’t throw it back in your pouch after you’ve located the studs. Use your stud finder to check the whole wall cavity for obstacles like blocking and abandoned headers. You don’t want to find out the hard way that you should have fished your wire one stud cavity to the left or right.
Running wire from a switch location to a light or fan in the center of the ceiling can be a challenging project. You'll almost always have to cut some holes in the walls, but you can minimize ceiling damage by using a “fish tape.” A fish tape is a long strip of spring steel used for pulling wires through walls and ceilings. They're available at hardware stores and home centers.
To map out the best path for the cable run from the switch to the light, first determine the ceiling joist direction. Generally, it's best to run the cable in the space between the joists so you won't have to cut a lot of holes in the ceiling. Then figure how to get the cable through the wall to that joist space.
Since you can't run the cable through the attic, the next best choice is to go down into a basement or crawl space, then go back up through the stud cavity directly below the joist space. If you can't go down, follow the procedure we show here, which is to go horizontally across the studs until you're below the joist space. As you can see in Photo 2, you'll have to notch each stud and the top plate.
Once you know the path of the cable, cut a hole in the ceiling for the chandelier outlet. At each location where the cable will cross a framing member, cut away the drywall. Where the cable will turn from the wall to enter the ceiling, cut out a 3-in.-wide section of drywall in the wall and ceiling (Photo 1). Extend the openings at least 2 in. from the edge of the top plate.With a sharp 5/8-in. or 3/4-in. chisel, trim the stud or plate back about 1/8 in. so that the guard plate will sit flush with the face of the framing (Photo 4). Then chisel the notches for the cable (Photo 2).
Feed the fish tape from the opening at the top plate to the lighting outlet, connect the cable and pull it through (Photo 3). Then feed the fish tape from your wall switch to the top plate opening, connect the cable and pull it through the wall.
Be sure to install nail guards that completely cover the cable where it crosses the framing (Photo 4). Wire the switch and the lighting outlet, then patch the holes in the wall and repaint.
The Tools You Need
Flex bits, glow rods and fish tapes are the tools electricians use to fish wires and communication wire. Flex bits are great for drilling holes in hard-to- reach spaces (see “Invest in a Bumper Ball,” below). The two most common lengths are 5 ft. and 6 ft., but extensions are also available. A 3/4-in. x 54-in. flex bit costs about $50 at home centers. Buy a bit that has a hole on the end of it so you can use the bit itself to pull wires.
Once your hole is drilled, you can shove a fish tape or glow rod through the hole, attach your wire to the eyelet at the end and pull it back through. Glow rods can also be used to hook wires to pull them out. As their name suggests, glow rods glow in the dark. This makes them easier to spot when you’re working in dark areas (which is most of the time).
Glow rods come in various lengths and thicknesses, and you can combine as many sections as the job requires. Thinner rods flex more and work better when you have to make sharp turns. A thicker rod can span longer distances and is better for hooking wires that are more than a few feet away. A 9-ft. glow rod kit costs about $40 to $50 at home centers. You can also buy a 24-ft. kit.
When hooking a wire to pull it toward you, make sure there’s more than enough wire to hook on to. Sometimes it’s a real challenge to grab hold of a wire, and once you have it hooked, you don’t want to lose it. Make sure you have at least 5 or 6 ft. of extra wire to keep up the tension on the hook as you’re pulling on it.
Sometimes you don’t need to use glow rods at all. Most flex bits have holes in the ends of them. If you have access to where the flex bit pops out, attach your wire directly to the bit and fish the wire through that way. Twist the wire and tape it up to make sure it doesn’t come off when you’re pulling it back through (see “Hold On Tight” below). Remove your bit from your drill before pulling so you don’t accidentally spin the bit and twist up your wire.
Seal the Holes
If you’re drilling holes through top and bottom plates or running wires through a fire wall in the garage, you must seal those holes with a fire-resistant caulk or foam sealant to comply with fire and energy codes. Most building officials won’t make you bust out large holes in ceilings and walls in order to access hard-to-reach holes, but check with your local official before you begin your project. A can of fire-blocking insulated foam sealant costs about $10 at home centers and hardware stores.
When you’re installing new recessed can lighting, fishing wires from one light to another is easy because you have a great big hole to pull the wires through. But even if you’re not installing new lighting, you can use the existing openings. Many cans can be easily popped out of the opening by removing a few screws.
Mud rings, also called drywall brackets or low-voltage “old-work” brackets, are great for protecting the drywall when you’re drilling with a flex bit or cranking on a glow rod. They’re easy to install and only cost a few bucks at home centers. Once the wires are connected, you can screw the wall plate to the mud ring. However, mud rings are approved only for low-voltage wires like coaxial cables. If you need to install a regular gang box for a receptacle or switch, install the mud ring temporarily while you fish the wire.
Wires aren’t supposed to be installed any closer than 1-1/4 in. from a penetrable surface (the outside of the drywall). That means you shouldn’t be drilling holes right next to the drywall. But it’s not always easy to control where a flex bit goes. A Bumper Ball flexible drill bit guide installed on the end of your flex bit will help maintain the proper space between the bit and the outside of the wall cavity.
When you hook cable to the eyelet of a glow rod, strip the plastic sheathing back about 6 in., then cut off the hot and neutral wires. Wrap the remaining ground wire through the rod’s eyelet and wrap it back around the wire’s sheathing several times. Finally, wrap the whole area with electrical tape. When hooking coaxial cable, just tape the whole wire to the glow rod. Use the same technique when working with communication cable like phone wire.
Don’t Spin Apart the Glow Rods
Sometimes you need to twist and spin glow rods in order to snake them past ductwork, pipes and other obstructions. A great way to lose a rod or attachment in a wall or joist space is to twist it so many times in the same direction that it unthreads and comes apart. Some pros wrap a little electrical tape around the connections to keep them secure.
You know your wire is in there somewhere, but you just can’t seem to find it. It’s probably hung up on another wire or pipe, but guessing isn’t going to solve the problem. The solution is to shine a flashlight onto an inspection mirror to find out exactly what’s going on. This is a simple, inexpensive tip that can save you a lot of time and frustration. Pick up an inspection mirror at an auto parts store. Or pay a few more bucks for a mirror with small built-in lights, so you can see exactly what’s going on.
The best advice for fishing wires through insulation is “Avoid it if you can.” The potential is always there to damage the vapor barrier or bunch up insulation, leaving cold spots in the wall. If you must fish wires through exterior walls, the best tip is to avoid spinning the flex bit until you make solid contact with the wood you plan to drill through. If you drill too early, you’ll end up creating a large insulation cotton candy cone, which will make retrieving your bit difficult, if not impossible.
It’s really tempting to fish low-voltage wires (like coax and Cat-5e) through existing holes occupied by electrical cables, but don’t do it! Even though cables are insulated, the high-voltage current can interfere with the signal in the low-voltage wires. This could result in bad TV reception or unreliable phone and Internet service. Drill a new hole, and keep the new low-voltage wire several inches away from electrical cables. It’s OK to run low-voltage wires perpendicular to cables, and it’s also OK to run low-voltage wires next to electrical wires that are encased in conduit or metal sheathing.
Buy Extra Wire
Have plenty of extra wire or cable on hand, because i’s not likely that you’ll be able to fish a wire in a straight line from Point A to Point B. There’s also the possibility that your wire might get hung up on something, and you'd have to abandon it and start over.