In-deck lighting can be a both functional and attractive addition to your outdoor deck. Flush-mounted in the deck floor, these lights are unobtrusive and can be walked on. You may think you need to hire a professional to get the job done right, but this is actually a moderately easy do-it-yourself job when you have the right tools and instruction.
Buy an in-deck lighting kit with the number of lights you require, or buy the lights separately if you need an odd number. In-deck lights are available from most home improvement retailers.
Add up the total wattage of the in-deck lights you plan to use.
Buy a low voltage transformer with enough wattage capacity to work with the total wattage of your deck lights.
Position your in-deck lights roughly where you would want to install them.
Measure the distance of each light from where the transformer will be, and add up the measurements to get the total length of wiring you will need.
Order at least 10 percent more outdoor wiring than you need. You don't want to accidentally run out of wiring in mid-job.
Cut 7.5 cm (3 inch) flat-bottom holes in the deck floor where you want to install the lights using the forstner drill bit. Don't allow the drill bit to go all the way through the wood. Keep the drill perpendicular to the deck floor throughout the cut.
Drill 2.1 cm (7/8 inch) through holes in the centers of the 7.5 cm (3 inch) flat-bottom holes using either a spade or auger drill bit. These holes are for the wiring bases of the in-deck lights.
Place the lights into the holes.
Connect the lead wires on the lights to the 12-volt outdoor lighting wire from beneath the deck.
Wrap the connections with electrical tape for safety.
Run wires under the deck to the transformer and connect them. Staple the wires to the underside of the deck to keep them flush with the surface.
Check that you will have access to a 110-volt power outlet for you deck. If not, you should have an electrician install one before you begin.
Transformers can experience what's known as "voltage drop." This is when they lose some voltage along the wiring. To prevent this from affecting your in-deck lighting project, use a transformer that has a slightly higher wattage capacity than you need. When stapling wires to the underside of the deck, be careful not to staple through the wire. This is a dangerous hazard.