How to Hide Wiring for Deck Lights

Written by mark morris
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How to Hide Wiring for Deck Lights
An extendable spade bit can core a post for light wiring. (drill press image by Nancy Ottenweller from

One of the most effective ways to install lighting on decks is in the form of post cap fixtures. These are available in low-voltage styles that can be installed by any homeowner without an electrician. To conceal the lights, the post will need to have a hole drilled down its centre in a process known as coring. It is easiest to core deck posts once they are already installed. The connecting wires will need to run underneath the deck to complete the project.

Skill level:

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Things you need

  • Rafter square
  • Drill
  • 1-inch extendable spade bit, with extensions
  • Allen wrench
  • Wire
  • Light fixtures
  • Wire nuts
  • Nail-type wire clamps
  • Plug

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  1. 1

    Install your deck rail posts leaving the top open. Use a rafter square to mark the centre of the post top. Install the end section of your spade bit extension set with a one-inch wide spade bit. Bore the hole down as far the bit will go. Keep the drill turning as you pull it up and out, shedding the shavings as it comes.

  2. 2

    Remove the bit and install the first 12-inch extension section in the drill. Loosen the two Allen head set screws and insert the spade bit end section into the extension and tighten the set screws. Stand on a step stool or short ladder to operate the drill properly. Bore down to the end of the spade and extension bit sections, a total of 24-inches, working to keep the bit centred in the post. Keep the drill turning and pull it back out.

  3. 3

    Add a second and final extension section to make the bit 36-inches long. Bore down to the end of the bit. With a standard rail height of 32-inches, this will put you three-to-four inches below the surface of the deck.

  4. 4

    Install just the end spade bit section into the drill. Locate the post you drilled at its base under the deck. Bore horizontally into the core channel you bored at a right angle to the initial hole.

  5. 5

    Feed your wire up through the hollow centre of the post, running out through the horizontal hole under the deck. Use nail-type cable clamps to nail the wire along the bottom edge of the joist to the next post location. Bore this post in the same way as the first one. Run the wire up through the post. Continue boring each post in turn, running wire into each post.

  6. 6

    Run the wire from the last post to the edge of the deck nearest your outlet. Install each deck light on top of the post. Use wire nuts to connect the wires, black-to-black, white-to-white and green-to-green. Use wire nuts to make the connections. Fasten the lights to the top of the posts according to the accompanying installation diagrams. In general, attach the cap section of the light fixture with the supplied screws. Install the light bulb and fit the light globe, or other shade onto the fixture.

  7. 7

    Connect the ends of the wire to a male plug. Remove the two screws in the end of the plug. Slide the cover sleeve back to expose the screw terminals. Strip the ends of the wires back with wire strippers. Select the correct notch in the stripper's jaw and fit the wire into it, squeezing the stripper closed completely. Wrap the black wire around the copper or brass-coloured screw terminal, connect the white wire to the nickel-coloured terminal and attach the green to green. Slide the cover in place. Replace the two screws in the plug's end and tighten with the screwdriver. Insert the plug into the outlet to supply power to the lights.

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