How to Wire an Outdoor Light Fixture

Most outdoor lights and alarms are designed to be weatherproof, the quality that clearly differentiates them from indoor fixtures. Made of weather-resistant material, outdoor fixtures come with a rubber gasket to seal out moisture. If no gasket is supplied with the fixture or you are recycling an old one, you can use silicone caulk in place of the gasket. Except for that, the installation process is the same as it is for an indoor fixture.

Step 1

Make sure the power is off to the electrical box and, if you have to use a ladder, be sure to secure it before you start.

Step 2

Seal any gaps you find between the electrical box in the wall and the siding with silicone caulk. Cut the end off a tube of silicone caulk, mount it in a caulking gun and squeeze enough caulk into the gap to adhere to both sides of the gap. Use any small, flat stick to smooth it down so that it closes the gap.

Step 3

If the fixture came with a strapping plate to attach it to the box, screw this plate into the two holes on either side of the box. Use the machine screws that came with the fixture.

Step 4

Prepare the ROMEX® wire in the box: Measure out about 6 inches and cut around the plastic sheathing with a utility knife, being careful not to cut into the wire strands underneath. Pull off the sheathing. Use the splicing tool to remove about 1/2 inch of plastic from the ends of the black and white wires. Pass the wires through the rubber weatherproofing gasket, if there is one.

Step 5

Use a green grounding screw to attach the bare ground wire to a metal box to ground it. If the fixture has a ground wire, twist the ground wires together and wrap them around the grounding nut in the box, if there is one. Push the wires directly into a plastic wire nut to keep them out of the way. Using pliers, twist the white wires from the box and the fixture together in a clockwise direction. Screw on a wire nut. Repeat with the black wires. Push these wires into the box, making sure the nuts are separated from each other.

Step 6

Seat the fixture against the wall with the gasket in between and affix the fixture to the box using the screws that are provided. Make sure it is tight.

Step 7

If there is no gasket, apply a bead of silicone caulk around the outside of the fixture where it contacts the wall.

Step 8

Turn on the power.


  • It is critically important to ground outdoor fixtures since they become especially hazardous when they are wet. If there is no grounding wire in your house circuitry, consult an electrician.

About the Author

Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.