How to Add an Outdoor Outlet

Overview: A simple wiring technique

Most homes have only two exterior outlets—one in the front and one in the back. That may be OK most of the year, but it's a real hassle when you're hanging holiday lights. It can be dangerous, too: Overloading cords or outlets poses a fire hazard, while crisscrossing your driveway and sidewalk with cords creates tripping hazards.

In just a few hours, you can solve these problems forever by adding an outlet or two. In this story, we'll show you how to do just that. We've made adding an outlet as easy as possible—simply connect new wire to an existing interior outlet and install your new outlet on the opposite side of the wall. This eliminates the arduous task of fishing wires through finished rooms. To bypass the hassles of cutting a boxed-size hole in the exterior wall, mount the new outlet right to the siding.

Even if you've never worked with electricity before, you can do this. Our Web site covers all of the basic skills you need to complete this project safely (visit thefamilyhandyman.com). Everything you need is available at home centers for less than $60. Call your local inspections department to apply for a permit before you start.

Step 1: Choose and mark the outlet location

1 of 1

Photo 1: Drill through the exterior wall

Drill a 1/4-in. hole alongside an existing electrical box to mark the location of the new outlet. Go outside and drill a 3/4-in. hole in the siding over or near the smaller hole.

To keep this project simple, place the new outlet in the same stud cavity as an existing indoor outlet. Start by choosing the interior outlet you want to use. Building codes prohibit tapping into circuits in the kitchen, bathroom, laundry room or into those dedicated to a large appliance, like a refrigerator. You can use living room, bedroom and basement circuits, but don't tap into a circuit that's already overloaded and trips the circuit breaker. To place the outlet somewhere other than opposite the interior outlet, see “Running Cable From Other Power Sources” below.

Turn off the circuit breaker controlling the outlet. Use a noncontact voltage tester to be sure the power is off. Then unscrew and pull the receptacle out of the electrical box. Hold the voltage tester over the terminals to double-check that the power is off. Next, unscrew the wires from the outlet. Make sure the junction box is large enough to hold an added set of wires. (An overstuffed box is a fire hazard.) If the box is plastic, shine a flashlight inside and look for a volume listing, such as 21 cu. in. (cubic inches). If your box is metal, we recommend that you replace it (see “Replace an Electrical Box,” below). Most metal boxes are too small to hold additional wires.

Use a stud sensor to determine which side of the electrical box the stud is on. Place a 1/4- x 18-in.-long drill bit along the outside of the electrical box on the side away from the stud. Squeeze the bit between the box and the drywall. But don't worry if you make a small hole in the drywall. You can hide it later with the outlet cover plate. Drill through the wall and through the siding to mark the location for the new outlet (Photo 1). We tilted the drill bit downward to lower the outlet location (if it's near the ground you can hide it behind shrubs), but you can place it anywhere on the wall.

Find the marker hole outside and place the exterior junction box over it on the siding. If that's not where you want it located, move it straight up or down (staying in the same stud cavity) and mark the position of the box hole on the siding. Then drill a 1-in. hole over the smaller hole or the mark on the siding to make room for the cable.

If drilling through stucco, you'll probably wreck the bit, but you'll get through the siding. For brick, use a masonry drill bit with a hammer drill. Then drill a series of small-diameter holes around the marker hole and knock out the center with a hammer and chisel.

Figure A: Run a cable from a basement

Figure B: Run wires inside conduit

Running Cable From Other Power Sources

If you don't want your exterior outlet location limited to where you have interior outlets, you'll have to tap into another electrical circuit. If you have an unfinished basement, you can tap into a junction box in the basement and run the cable out through the rim joist. This is even easier than tapping into a main floor outlet. Plus, it allows you to put your new outlet anywhere, not just opposite an interior outlet. Simply drill a hole through the rim joist and siding, then run a cable from a basement light fixture to the outlet location (Figure A).

A second option is to run wires inside 1/2-in. metal conduit from an existing exterior outlet to the new location (Figure B). The conduit can wrap around corners with a service ell, but don't run it in front of doors. Plant flowers or shrubs in front to cover it.

Step 2: Run cable between the outlets

1 of 1

Photo 2: Pull in the new cable

Cut off 2 ft. of sheathing and two wires from the cable. Tape the remaining wire to the sheathing, then feed the loop through a knockout in the interior box. Fish for the cable from the exterior hole using a hook made from wire. Pull the cable through the hole.

The new wire must be the same gauge (thickness) as the wire already in the box, which is most likely 14 gauge but could be 12. To check, use the labeled notches on wire-stripper pliers.

Run cable from the interior box to the hole in the exterior. Start by removing a knockout in the box by hitting it with a screwdriver. Then strip about 2 ft. of sheathing off the end of the cable and cut off two of the three wires. Tape the end of the remaining wire to the end of the sheathing, forming a loop. Feed the loop through the knockout into the wall cavity.

Bend the end of a wire coat hanger to form a hook. Insert it through the hole in the exterior, grab the wire loop in the wall and pull it back through the hole (Photo 2). Pull through at least 12 in. of cable to give yourself plenty to work with.

Photo 1: Cut the nails that fasten the box to the stud
with a hacksaw blade. Pull out the box and loosen
the clamps that hold the wire.

Photo 2: Enlarge the wall opening for a remodeling box.
Feed in the new and old cables, then mount the box.
Caulk any gaps between the box and the wall.

Replace an Electrical Box

If your existing electrical box isn't large enough to hold more wires, you'll have to replace it. Remove the old box before cutting a large opening for the new one. This allows you to see if anything is behind the wall before you make the cut.

To swap out boxes, cut the nails that hold the box in place (Photo 1). Then remove the box. Replace it with a plastic “remodeling” box. These boxes have wings that flip up and attach to the back side of the drywall or plaster. Hold the box over the wall opening and trace around it. Then enlarge the opening with a drywall saw. Don't overcut; you want a snug fit.

Feed the new cable from the outlet being added into the box before installing it (Photo 2). Wrap the cable with electrical tape where the sheathing meets the exposed wires so the sheathing will slide into the box easier.

Step 3: Wire the interior outlet

1 of 1

Photo 3: Rewire the existing outlet

Strip 12 in. of sheathing from the cable in the interior box. Strip 3/4 in. of insulation off the ends of the wires. Fasten the pigtail wires to the outlet, then join the wires with wire connectors.

At the interior box, cut the cable so there's 12 in. sticking out, then remove the sheathing to expose the wires. Cut 6-in. pieces of wires from the coil and strip 3/4 in. of insulation off the ends. Screw these short pieces to the outlet: The bare copper goes to the ground screw (green), the white to either of the silver terminals, and the black to either of the brass screws on the other side. Hook the wires clockwise over the screws so they stay in place as you tighten the screws.

To wire the interior outlet, connect all of the hot wires (black and any other color except green or white), all the neutral wires (white), and all of the ground wires (green or bare copper as shown in Photo 3).

Gently fold the wires into the box, then reattach the outlet and cover plate. If you damaged the wall around the box, use an oversize cover plate to hide the problem.

Step 4: Mount and wire the new outlet

1 of 1

Photo 4: Wire the exterior GFCI outlet

Attach a clamp to the box, feed the cable through it into the box, then caulk around the clamp. Mount the exterior outlet box to the house. Wire the outlet and set it in the box.

We used a TayMac weatherproof receptacle kit for our exterior outlet. It came with a standard three-prong outlet, but since outside outlets must be GFCI protected, we replaced the kit outlet with a GFCI outlet.

Attach the two mounting lugs to the back of the metal electrical box, putting them in opposite corners. Fasten a clamp to the hole in the back of the box, then feed the cable through the clamp. Apply a heavy bead of silicone caulk around the clamp and place the box on the wall, inserting the clamp into the hole in the siding. The caulk makes the hole watertight. We placed our box horizontally on the lap siding so it could lie flat.

If you have lap siding (wood, hardboard, fiber cement) or plywood sheathing, mount the junction box to the house, using exterior-grade fasteners. Simply drive galvanized deck screws through the mounting lugs. For brick or stucco siding, mount the box with masonry anchors. For vinyl siding over composition board, use hollow wall anchors.

Fasten plugs into the openings on both ends of the box. Use a file to scrape a small notch or “weep hole” in the bottom edge of the box. This allows any water that gets into the box to drain.

Next, strip insulation off the wire ends. Attach the ground wire to the green screw in the box and to the green screw on the GFCI outlet. Make sure to identify the line, hot and white terminals (they'll be labeled “line,” “hot” and “white.” Attach the black wire to the brass screw or adjacent push-in hole (labeled “line”)and the white wire to the silver screw or push-in (Photo 4). Clip the ears off the outlet, fold the wires into the box and set the outlet in place.