Illuminate Your Deck With Low-Voltage Light Fixtures

Overview

Don't let nightfall drive you indoors this summer. Instead, illuminate your deck. Once you see the effect of highlighting your favorite plants and deck features, you won't want to go inside. And there's a safety factor, too. If you light the stairway and railings, you won't trip over the garden hose!

In this article, we'll show you how to plan and install a low-voltage system. The 12-volt system we show here has several distinct advantages over standard household (120- volt) wiring. It's much less dangerous, and the actual wiring methods are less exacting. Even if you're a beginner, you can safely install a simple system like ours.

A low-voltage system begins with a transformer that plugs into a standard GFCI exterior receptacle. The transformer converts the power from 120 volts to 12 volts and sends the current through special outdoor cable to light the fixtures. The only special tool you'll need to install this system is a wire stripper. The rest are just basic carpentry and garden tools.

To light the deck and the landscape around it, we used 13 fixtures, two transformers, cable and connectors. Pay close attention to the planning section and drawing, and follow our photo series for techniques and tips on how to safely wire your low-voltage system.

Our deck lighting layout in Figure A features a variety of fixtures and mounting methods to show the different methods of running cable to individual locations and determining the wattage loads for each circuit. Follow the dotted lines for each circuit to the type of fixture we used in our story.

Planning your lighting

One great feature of a low-voltage system is the wide variety of fixture finishes and shapes to choose from to complement your home. You'll find a limited selection at home centers, but a wider variety at local lighting specialty stores and through online catalogs. Keep in mind that you can buy complete ground-level landscape lighting kits, but you'll have to buy individual components (transformer, cable, fixtures, lamps and connectors) for a deck lighting system.

Before you buy anything, make a sketch of your deck along with the chairs and tables. To simulate the effect of each fixture on and off your deck, buy an inexpensive clamp-on work light with a metal reflector shade. Along with the clamp light, buy 25- and 40-watt standard frosted incandescent bulbs and a 45- or 50-watt reflector flood bulb. As evening approaches, install the 25-watt bulb and plug the clamp light into an extension cord. Then clamp the lamp at different locations on your deck, turn it on and observe the lighting effects. This will simulate the various fixtures we used in our deck plan. Keep the light low (about 2 ft. off the deck surface) to prevent glare. Try a 40-watt bulb if you want more light. Mark the most desirable locations on your drawing.

Pay particular attention to lighting areas like the stairway and transitions to different deck levels. For these locations, install the spot bulb for more focused light.

Now take the clamp light into the yard around the deck and clamp it to various stakes so you can see where you can illuminate a path, plants or other features along the perimeter of the deck. Mark the best spots on your drawing. You'll want to incorporate several lighting techniques for a variety of useful and decorative effects.

Match the transformer to the wattage of the circuit

We chose two lighting circuits, each controlled by its own transformer with built-in timer, as shown in Figure A. This plan gave us several options. The circuits could go on and off at different times and we could create a dedicated deck lighting plan and another landscaping plan. Once you figure out how many lights you'll have on each circuit, add up the wattages and buy large enough transformers to power each circuit. (If you buy a landscape lighting kit, all the materials and connectors will be included.) Transformers generally come in 100-, 150-, 300-, 600- and up to 1,000-watt capacities. The total wattage of all the lamps in an individual circuit must not exceed the wattage rating of the transformer circuit. Follow these guidelines:

• Add the wattage for the seven lights on the deck: four lamps at 26 watts and three at 35 watts, for a total of 209 watts. You may want to add a lamp or choose a brighter bulb later, so use a 300-watt transformer for this branch.
• Next, calculate the total wattage for the perimeter of the deck. We had six lights. Five of the lights had 50-watt bulbs; the other had an 18-watt. This added up to 268 watts, so we selected another 300-watt transformer to supply power for the landscape circuit.
• The transformers plug into a 120-volt exterior receptacle (Photo 1), so if there's not one nearby, you'll need to install one or have it installed by an electrician.

Cable and connectors complete the package

You'll also need to buy cable for your light fixtures. Don't skimp here. If you have long runs of 50 ft. or more as we did, buy 12-gauge outdoor lighting cable and you won’t have to worry about a voltage drop along the circuit that could dim the lights near the end of the line. Measure the total distance from the transformer to the last light of each circuit and buy an extra 20 percent for unforeseen paths that wire may have to take.

You'll need two types of cable connectors: one for dry areas inside the panels and planters and another for wet areas where the cables will be buried in the soil outside of the deck. The first type (Photo 5) is a standard wire connector used in common house wiring connections. The other connector (Photo 8) is filled with a sealant that coats the wires as you twist the connector onto the bared ends of the wire. These cannot be reused but offer excellent protection for years of service. Also buy some cable fasteners to secure the cable to the deck framing (Photo 2).

Installation

The photos show the basic installation steps. Start at the transformers (Photo 1) and run the cable in the shortest route to all the lights. In general, run the cable out of sight as much as possible and be sure it's protected. You don't have to make connections inside electrical boxes as with 120-volt systems. Mounting procedures vary, so read the directions included with your fixtures. If you want to add more lights or change to brighter lamps, be sure your transformer can handle the extra load.

Note: Do not run the cable into concealed areas like the exterior walls of your house. If you want lighting mounted to the walls of your house, you'll need to buy 120-volt fixtures, follow conventional wiring methods and have your work inspected by your local electrical inspector.