How to Install an Outdoor Electrical Outlet Box

Updated February 21, 2017

Outdoor electrical boxes use rubber gaskets to seal its weatherproof lid, cover plate and box together. A properly installed outdoor electrical socket box keeps moisture away from live wires. The moisture not only corrodes the outlet's metal parts, but it can conduct electricity to an exposed area of the electrical box. Many local building codes require outdoor electrical-boxes contain ground fault circuit interrupt (GFCI) outlets. These outlets, which detect differences in the electrical current flowing in and out of the outlet, will turn the electricity to the electrical box's circuit off if a short develops.

Choose an interior electrical socket that mounts in an exterior wall. The new exterior electrical socket will tap into this outlet's electricity feed. Turn the circuit breaker that controls this room and outlet, off.

Unscrew the wall outlet's cover plate with a flathead screwdriver. Remove the cover.

Unscrew the outlet's two retaining screws with a flathead screwdriver. Pull the outlet from the box and push it to the side.

Remove one of the round disks, called the knockout disk, from the rear of the interior outlet box. If the knockout disk contains a slot, then insert a flathead screwdriver in the slot and twist the slot until the knockout disk breaks free. If not, then place a flathead screwdriver's blade on the knockout disk and strike the screwdriver's handle with a hammer until the disk breaks free.

Place a 3/8-inch drill bit in a drill-bit extension and tighten its locking screws with an Allen wrench. Secure the drill-bit extension in a drill.

Push the drill bit through the knockout disk's hole in the back of the interior outlet box then drill a hole through the exterior wall.

Remove a knockout disk from the rear of an outdoor electrical socket box.

Apply a 1/4-inch wide bead of exterior grade caulk around the perimeter of the rear of the outdoor electrical box. Keep this bead between 1/4 and 1/2 inch from the edge.

Line up the hole on the back of the outdoor electrical box with the hole drilled through the exterior wall. Push the outlet box against the wall.

Secure the box to the wall with 1-inch screws. Drive the screw through the mounting holes found inside of the box.

Cut a piece of 12-2 wire with ground wire 18-inches long with wire cutters. 12-2 with ground wire has two insulated 12-gauge wires and an uninsulated 12 gauge wire. Push about 12 inches of this wire through the hole in the back of the outside outlet box and into the interior outlet box.

Fill the hole in the exterior wall around the 12-2 with ground wire with exterior grade caulk.

Strip 1/2 inch of insulation from the end of each 12-2 wire with wire strippers.

Attach the stripped ends of the wires that penetrate the outdoor electrical box to a GFCI outlet. Wrap the black insulated wire around the gold-coloured screw, the white insulated wire around the silver coloured screw and the uninsulated wire around the green screw. Tighten each screw with a flathead screwdriver. Repeat this for the inside outlet.

Push each outlet into its respective electrical box. Tighten the outlet's retaining screws with a flathead screwdriver. Each outlet holds two screws.

Screw the outlet cover-plates to the electrical boxes with a flathead screwdriver. Make sure the outdoor electrical box's cover contains its rubber gasket before attaching the cover to the box.

Things You'll Need

  • Flathead screwdriver
  • Hammer
  • 3/8-inch drill bit
  • Drill bit extension
  • Allen wrench
  • Drill
  • Exterior-grade caulk
  • 1-inch screws
  • 12-2 wire with ground wire
  • Wire cutters
  • Wire strippers
  • GFCI outlet
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About the Author

Based out of Central Florida, Robert Sylvus has been writing how-to and outdoor sports articles for various online publications since 2008. Sylvus has been a home improvement contractor since 1992. He is a certified HVAC universal technician.