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Illuminate Your Deck With Low-Voltage Light Fixtures

Updated: Jun. 30, 2017

Stay up late: Enjoy your deck well into the evening hours

FH06MAY_ILLDEC_01-2Family Handyman
Low voltage lighting is simple and safe to install on decks, patios or around the garden, even for beginners. Learn about lighting options and installation techniques.

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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.

Figure A: Deck Lighting Layout

Use only outdoor UL-listed lighting transformers, cable and lights for your project. If you plan to purchase individual components instead of a kit, check with the product manufacturers to make sure your components are compatible.

See below for photos and descriptions of the lights used in this layout.

Planning your lighting

A: Surface-mounted 12-volt lights

Surface-mounted 12-volt lights cast a soft pool of light onto the deck surface. These are perfect for mounting to posts or other flat surfaces.

Close-up of surface-mounted 12-volt lights

You’ll need to drill a hole behind the fixture to hide the wire or create a false panel behind the fixture to conceal the wire.

B: Recessed 12-volt lights

Recessed 12-volt lights diffuse the light for soft general lighting. You’ll need a hollow area like our deck planter or stair riser to mount this type of fixture. They are not to be mounted in an exterior wall of the house.

Close-up of recessed 12-volt lights

These lights are sized to fit in stair risers.

C: Surface-mounted 12-volt bullet lights

Surface-mounted 12-volt bullet lights are perfect for mounting to posts or exterior panels. The base threads onto the fixture and has a 360-degree adjustment for exact focus.

Close-up of surface-mounted 12-volt bullet lights

Use 35-watt spot or flood lamps in bullet lights.

D: Staked bullet lights

Staked bullet lights (12 volt) are designed for ground-level lighting to silhouette plants or illuminate architectural features of the deck or house. They have a swivel mount for exact focusing. Use a 35- to 50-watt spot or flood lamp.

Close-up of staked bullet lights

Staked bullet lights are good accent lights.

E: Pathway lights

Pathway lights are designed to illuminate paths and low-lying plants.

Close-up of pathway lights

These 12-volt lights are stake mounted and generally take 9- to 18-watt lamps.

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

Photo 1: Transformer

Mount the transformers near the exterior receptacle. Leave enough cable to connect to each transformer later. You can connect to the transformers once you’ve wired 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

Cable connectors

Use waterproof connectors anywhere wire might get wet. Standard connectors are used in dry locations.

Photo 2: Run cable

Fasten the supply cable out of sight under the deck using cable clamps. Drill holes and run it through framing as needed.

Close up

Buy cable clamps for outdoor wiring.

Photo 3: Fish cables

Mark and cut the holes for the recessed fixtures, then fish the cables through the holes. Leave at least 6 in. of extra cable to work with. Strip about 3/4 in. of wire and connect the ends to the fixtures with cable connectors.

Photo 4: Install fixtures

Push the wires into the recess behind the fixture, screw the fixture to the siding and install the lamps and cover.

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).


Photo 5: Surface-mounted fixtures

When you’re installing a surface-mounted fixture, drill a 3/4-in. hole, slip the wires and connectors through, make the connections and mount the fixture.

Photo 6: Installing lamps

Install the lamp in the fixture socket. Use a small cloth or tissue to protect the bulb. The oils on your skin can cause premature lamp failure.

Photo 7: Surface-mounted spotlights

Position surface-mounted spotlights about 2 ft. above the staircase. Make sure you can fish the wires; you may have to drill through some posts.

Photo 8: Bury wires and connectors

Aim the ground-level spots, and join the wires with waterproof connectors. Then bury the cable and connectors 6 in. deep.

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.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • 4-in-1 screwdriver
  • Cordless drill
  • Electrical tape
  • Jigsaw
  • Level
  • Non-contact voltage tester
  • Spade
  • Wire stripper/cutter
You’ll also need an electrician’s fish tape.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • Cable clamps
  • Cable connectors
  • Low-voltage cable
  • Low-voltage fixtures
  • Transformer