How to fit deck lighting

Video by Wickes. This walk-through is based on the video “How to Install Deck Lighting with Wickes” from the Wickes YouTube channel, which covers planning the layout, drilling the deck boards, feeding the cable, and connecting the transformer. Good to watch before you buy anything — the light spacing and cable management sections are particularly useful.

1. Plan your lighting layout before buying anything

Sketch the deck and mark where you want each light. Most people space recessed deck lights at roughly 400–600 mm apart along the board edges or in a staggered grid pattern across the surface. Resist the urge to cram them in — LED deck lights are surprisingly bright and you end up with a landing-strip effect if they are too close together.

Count up the lights and check the wattage against the transformer you are buying. Every transformer has a maximum load rating — if you exceed it, the lights will dim or the transformer will cut out. Low-voltage 12 V systems are the norm for decking because they are safe to work with and the cable can run through the deck void without conduit. Most kits sold at Wickes or B&Q work on this principle.

2. Choose the right light pods and cable

Recessed deck lights typically need a hole between 45 mm and 65 mm diameter depending on the fitting — check the spec sheet before you reach for the hole saw. Most pods come with a stainless steel or brushed aluminium bezel that clips or screws into the hole from above, with the body dropping down into the void beneath the board.

Use two-core outdoor-rated cable throughout — not standard bell wire, which will degrade quickly outdoors. For longer cable runs, check that the cable gauge is sufficient; thin cable over a long run causes a voltage drop that makes the LEDs at the far end noticeably dimmer. A 1.5 mm² cable is generally fine for runs up to about 10 m on a 12 V system.

3. Drill the deck boards and route the cable

Mark each light position with a pencil and centre punch before drilling. A hole saw in a cordless drill cuts through most softwood and composite decking cleanly. Drill from the top surface downwards — this keeps the top face clean and any breakout happens on the underside where it will not be seen.

Once all the holes are drilled, get underneath the deck and plan your cable route. The cable should run along the joists where possible, clipped every 300 mm with cable clips to stop it sagging. Keep it away from the ground to avoid standing water sitting against the insulation over the winter. If the cable needs to cross a joist, drill a small hole through the joist and thread the cable rather than cutting a notch — notching weakens the timber.

4. Connect the light pods in the deck

Most deck light kits use a daisy-chain connection — the cable runs from the transformer to the first light, then on to the second, third, and so on. Each light has a short tail with a push-fit or screw connector. Connect positive to positive and negative to negative — reverse polarity on LEDs will stop them working, though it will not damage them.

Push the body of each light down through the hole and feed the connector up through the void. Secure the connector to the main cable run, tuck the excess cable neatly to one side, and then push the bezel into the hole from above until it clicks or sits flush. Do not connect to the transformer yet — finish all the lights first, then test the whole run in one go.

5. Fit the transformer in a sheltered spot

The low-voltage transformer needs a mains supply from a weatherproof outdoor socket. Position it somewhere sheltered — inside a shed, under the deck stairs, or in a waterproof enclosure. The transformer itself may be IP-rated for outdoor use, but it will last longer out of direct weather. Most have a short mains lead; you may need an outdoor extension lead rated for permanent outdoor use if the socket is not close by.

Connect the low-voltage output cables from the deck to the transformer terminals. Tighten the terminal screws firmly — a loose connection causes flickering and heat build-up at the terminal over time. Some transformers have a built-in dusk-to-dawn sensor or a timer, which is worth using if you do not want the lights running all night.

6. Test the lights and tidy up the installation

Plug in the transformer and switch on. Walk the deck and check each light comes on. If one pod is out, the most common cause is a loose connector in the void beneath that board — pop the bezel out, disconnect and reconnect the join, and try again. If several consecutive lights are out, check the connection at the last working one as that is usually where the fault sits.

Once everything is working, secure any loose cable under the deck with additional clips, seal around each light pod with a small bead of clear exterior silicone if there are any gaps around the bezel, and replace any deck boards you lifted during installation. That said, leave the transformer plugged in for a few evenings before you close everything up permanently — better to spot a connection issue now than have to lift boards in January.

When to call a handyman

Call Richard if you need a new outdoor socket installed to power the transformer — that is mains electrical work and needs to be done properly and safely. He can also help if the deck is already laid and cable routing is difficult, if the transformer needs hardwiring rather than a plug connection, or simply if you want the whole job done in a day without the faff of hiring hole saws and cable clips for a one-off project. Plenty of gardens around Sandwich and the surrounding villages have decks that are just crying out for a bit of evening lighting.