This technique only works if you can use an outlet as a power source that’s opposite, or nearly opposite, the place where you want your new outlet. To determine whether you can safely use an existing outlet, follow the list below.
- If a switch or outlet is on a circuit that often blows its breaker or fuse, don’t make matters worse by adding yet another outlet to the circuit.
- Electrical codes restrict the number of lights or outlets that can be connected to one circuit. Typically, you can have no more than eight lights or outlets on a 15-amp circuit. To determine the amp rating of a circuit, just look at the number on its breaker or fuse in your main electrical panel. Turn off the circuit and test light switches and other outlets to determine exactly which lights or outlets are on a given circuit.
- Most electrical codes now require outlets in kitchens and bathrooms to be on separate 20-amp GFCI circuits. So before using the method we show here to add an outlet in a kitchen or bathroom, check with an electrical inspector. If you add an outlet to a kitchen or bath, it must be GFCI protected. Don’t power your new outlet from a kitchen or bathroom outlet.
- Codes also limit the number of wires that can enter an electrical box, depending on the inside volume of the box and the gauge of the wires. The outlet-addition methods we show here are based on the most common wiring (14-gauge wire on a 15-amp circuit) and an 18-cu.-in. box (typical inside dimensions are about 2 in. x 3-1/4 in. x 3 in. deep). If the circuit is 20-amp—which means thicker, 12-gauge wire—or if the existing box is smaller than 18 cu. in., you can’t wire a new outlet as we show here unless you replace the existing box with a larger one. Plastic box sizes are stamped on the inside at the back.
Always confirm the required box size with your local building inspector. In most regions, you have to obtain an electrical permit for this work from your local building department. This helps ensure a safe job.
TURN OFF the power at the main panel, unscrew the outlet and use a voltage tester to double-check that the power is off. With either lead touching a ground wire (bare copper), touch the other lead first to the neutral terminals (silver colored), then to the hot terminals (gold colored). If the light glows with either contact, the circuit is still live. Find the right breaker and turn it off.
STRIP about 10 in. of plastic sheathing from the new cable to expose the black, white and copper wires. Run the new cable, with sheathing, at least 2 in. up inside the box, and double over the excess wires to help hold the cable in place. Strip 5/8 in. of insulation off the ends and connect the wires from the new cable to the existing bundles—white to white, black to black, ground to ground. Use new wire connectors of adequate size for the four wires in each bundle.
MARK the opening for the new box and cut it out with a drywall saw. Fish for the new cable with a hook made from a wire coat hanger. Pull the cable through the opening cut in the wall. Then strip about 9 in. of sheathing off the end of the cable, insert the cable so the sheath extends about 1 in. into the box and mount the box in the wall as shown in Photo 5.
Once you’ve determined the outlet that you’ll use as a power source and have shut it off, use an electronic stud finder to locate the studs on both sides. You can put your new outlet anywhere between these two studs.
Hold the face of the new electrical box against the wall where you want it to go, and trace around it with a pencil. Cut out the hole with a drywall saw. Note: Be sure to buy a “remodeling” box that can be secured to the drywall, not one that must be mounted on a stud.
Next, unscrew the existing outlet on the other side of the wall from its box (Photo 1) and punch out one of the knock-outs at the back of the box using a screwdriver. Then feed the new cable through the knock-out into the wall cavity (Photo 2). Feed in enough cable to reach the new outlet location—plus about 1 ft. Connect the wires of the new cable to the existing wires (Photo 3). Pull the cable out through the new outlet hole in the wall (Photo 4) and feed it into the new box. Then mount the new box in the opening. Photos 3 and 5 show how the electrical connections are made. Finally, call the electrical inspector to check your work.
Before you tackle any part of this project, turn off the power to the circuit at the main electrical panel by switching off the breaker or removing the fuse.
- Before touching any bare wires or terminals on a switch or outlet, use a voltage tester on all the wires to make sure the power is off (Photo 1).
- If you have old, fabric-insulated wiring, call an electrician to recommend safe connections. With wiring like this, there’s usually no ground wire and it’s hard to tell the hot wire from the neutral, because both are coated with black insulation.