How to Install Post Cap Lights

For Wood Deck Railing

Installation instructions below are for hard-wiring scenarios in completely wood railing systems. These setups, while still very DIY friendly, are going to be the most complex. Remember each lighting brand and fixture has its own specific installation instructions, read through them to find exact tool sizing and steps. The overall instructions, however, are applicable to these fixtures no matter the scenario.

If you are working with a Plug and Play wiring system, then disregard the wire stripping, wire nuts, and main run of cable. You will simply be focusing on concealing your extension cables, connector hubs, and splitters.

If you are installing on a Composite or Metal railing system, then you will have more opportunities to discreetly tuck away your wires and connections. Within your posts and post sleeves or tucked within hollow rails; your wiring arrangement will be smoother.


Preparing Your Wood Railing

Installing low voltage lighting on wood railings, both new and existing, calls for a bit of prep work to hide your wires and connections. Here are some contractor tips to help hide your cables and let the beauty of your deck get all the attention:

using a table saw to route out a channel in the top rail to hide wires
Close up of finished top rail with channel to hide wire
Nylon Cable Ties

Nylon Cable Ties

Close up of Classy Cap Solar Deck light

Wire Concealing Wood Trim

Before you Begin

  •   On the first post of your railing, drill a hole for the wire to initially enter through. This should be on a more hidden face of the post.
  •   Even if not installing post cap lights, creating a cavity within your post core will allow you to discreetly hide wires and connections.
  •   On new wood railings, or one with a cap board installed across, route out a channel down the center of your top rails to hide your wire.
  •   For existing wood railing, or top rails that do not have a flat cap board installed across, cut a groove up into the underside of the rail. This will allow you to snugly tuck and hide your wire.
  •   For existing wood railing, you can also run your wire underneath the top rail and staple it every 4-6 inches.
  •   For beginning posts near the house, drill a ⅜ inch hole on an outside surface and into the center hole. From here you can run your wire from the transformer next to the house and out of sight.
  •   Can’t stand the wire running down the side of the post? Cover it with a piece of Wire Concealing Wood Trim.
  •   Connector hubs and splitters have built-in screw holes to keep the wiring up off the ground and out of sight. If you’re using wire nuts, then remember to purchase Nylon Cable Ties, which have a screw mount, to help keep wires secure in place.

Post Cap Deck Light Intallation

Drilling a hole in a wood 4x4 to conceal low voltage wiring
top view of deck post with a hole drilled in it to coneal deck lighitng wiring

Step 1

Looking down on the post, mark the center by drawing two lines diagonally from corner to opposite corner.

Step 2

With a 1-½ in to 2 in Forstner bit, drill a hole at the center of the "X" slightly deeper than the incoming wire level. After drilling holes in each post, go back and use a Shop Vac to clear away any wood shavings or debris.

A drill making a hole in side of wood deck 4x4 to accomidate for wires
a wood deck rail with a 2x4 that has a channel drilled out for wires

Step 3

Using a ½ in drill bit, create a hole from the side of the handrail post into the core of the deck post. If you’re creating a chain of lights, you may need to create holes in both sides of the post.

Running low voltage wire along a deck railing of wood rail
Running low voltage wire up a deck post and creatign a loop at the top

Step 4

Run the appropriate gauge of wire from the transformer to the first light, leaving a loop of extra wire at the top of each post.

New Decks: Run your wire from post to post in the railing groove you created before starting. Do not install the top rail until after the lighting system has been tested and verified to work!

Existing Decks: Loosely run the wire along posts and underside railings, threading them up and creating a loop in each deck post. Do not secure any of the wire with staples at this point.

cutting back wire for post cap installation
stripping wire for post cap installation

Step 5

Cut back any excess wire and leave enough exposed to make connections without creating excess bulk. Separate each wire pair into 2-3 in single strands. Using wire strippers, remove approximately ½ in of sheathing from each wire – including the wires on the light fixture.

twisting wire nuts to connect wires for post cap installation
close up of wire nuts installed on post cap installation

Step 6

Stay consistent in matching wire types as you continue through the wiring process. Most wires will have a “smooth” black wire combined with another wire that has white lettering – matching polarity is especially critical for LED lights.

Taking one wire from the light fixture and its counterpart from the wire threaded into the post, hold the two wires together with the ends even. Twist a waterproof wire nut onto them, pushing firmly until hand-tight. Don’t over-twist the connection. Then, repeat for the second set of wires. Wipe away any excess silicone sealant, and then wrap the connections with electrical tape to prevent accidental movement.

tuck the wires into the post for post cap installation
place post cap on post without fully securing it

Step 7

Tuck the wire and wire nuts into the recessed hole on top of the post, and place the cap in position. Don’t fully secure the post cap, handrail, or wiring until you have tested the entire lighting system.

closeup of low voltage ac transformer with photo eye
low volatege transformers installed

Step 8

ALWAYS READ AND FOLLOW THE INSTRUCTIONS THAT COME PACKAGED WITH YOUR TRANSFORMER BEFORE INSTALLATION. If the transformer has an accompanying photo-eye, make sure it’s exposed to direct or indirect sunlight.

Transformer with on off switch
transformer with tape over photo eye

Step 9

If the transformer has an on/off switch, verify the switch is in the "OFF" position before plugging the transformer into a timer or directly into a GFCI outlet. After connection to an outlet, turn the transformer switch to the "ON" position.

Tip – If the transformer has a photo eye built into the transformer, place a piece of tape over the photo eye for testing a low voltage system during daylight hours. It may take 2-5 minutes for the photo eye to respond after covering.

securing post cap deck light with supplied screws
Post cap lit and installed on a deck post

Step 10

Finish the wire installation. Having verified that the light system works, unplug the power source to the transformer.

New Decks: Secure the handrail’s top board, any other finishing boards and post caps. Take care not to hit any wires with screws.

Existing Decks: Secure the wiring along the posts and under the handrails by using the staple gun. Be sure to center the staple directly over the wires and DO NOT staple through the wire.