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How to fit outdoor lighting

Fit outdoor lights

Providing some form of lighting outdoors offers a variety of benefits.

Outdoor lighting can illuminate your path to the front door and prevent you fumbling for your keys in the dark; it can help you to see who is calling at night and deter criminals from lurking; it can allow you to make the most of a patio during warm summer nights; and it can create dramatic visual effects of light and shadow among the plants.

Tools and materials

Outdoor lights

Quantity: Optional

Cordeless drill

Quantity: 1

Light switch

Quantity: 1

Silicone sealant

Quantity: 1

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Installing a light on the house wall

Lights attached to your house walls – at the front and back doors, or on corners to illuminate pathways – can be fed by spurs from existing lighting or power circuits. It is advisable to incorporate an RCD so that the power will shut off instantly if a fault develops. Some modern consumer units incorporate this, but you may need to wire in a separate RCD to older types; if in doubt, check with a qualified electrician. Only fit weatherproof lights specially designed for outdoor use.

Connecting to a lighting circuit

A ground-floor lighting circuit will be the most convenient to supply outdoor wall lights, but make sure the additional fittings won’t overload it. If you want multiple outdoor lights or high-wattage floodlights, you may need to run a spur from a main power circuit (see below). Start by installing the light and switch, and run all the cables before isolating the circuit and making the final connections

1. At the light position, drill a hole through the wall so that it runs downhill slightly towards the outside. Line the hole with plastic conduit and feed the cable through.

2. Connect the cable cores to the appropriate terminals within the unit or to its flex cores using strip connectors, which you should wrap tightly in PVC electrical tape to keep out damp.

3. Attach the light to the wall and seal out moisture with a bead of silicone sealant around its base.

4. Inside the house, run the light supply cable back to a suitable position for cutting into a main lighting circuit cable with a four-terminal junction box.

5 Install a switch and run a length of 1mm2 two-core-and-earth cable back to the junction box position.

6 Isolate the circuit and double-check the power is off with a voltage tester. Then cut through the main circuit cable and make the connections in the junction box.

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Running a spur from a power circuit

If you decide to run an outside wall light off a main power circuit, first identify a suitable socket from which to run a spur. The spur must be run in 2.5mm2 two-core-and-earth cable to the ‘feed’ terminals of a fused connection unit containing a 5 amp fuse. If this has a switch, it can be used to turn the light on and off; otherwise, you will need a separate switch. From the ‘load’ terminals of the fused connection unit, run 1mm2 two-core-and-earth cable directly to the light (if the connection unit has a switch) or to a fourterminal junction box, from which you can run separate switch drop and light supply cables.

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Mains-powered garden lighting

Garden lights can be powered from a spur off a ring circuit, via a 5 amp fused connection unit. Once outdoors, the lights should be supplied by 1.5mm2 three-core steel-wire-armoured cable (SWA). Only fit weatherproof lights recommended for outdoor use. The circuit must have RCD protection.

Working with steel-wire-armoured cable

  • The cores of three-core SWA are coloured brown, black and grey. It is essential to fit green/yellow sleeving over the black core at every connection to indicate that this is being used as earth.
  • SWA should be buried: accidentally cutting through it could be fatal. Lay it in a trench at least 450mm deep under a path or driveway, or 750mm deep below unpaved areas that may be dug up at some point. Run electrical route marker tape above the cable at a depth of about 150mm as an extra precaution.
  • SWA must be secured to the house wall with SWA cable clips, fixed to the masonry with suitable plugs and screws, and protected where necessary.
  • Use a junior hacksaw to cut through SWA and pliers to strip back the armouring.
  • Connect the SWA cores to those of 2.5mm2 two-core-andearth cable in a weatherproof adaptable box fixed to the house wall. The SWA must enter the box via a purposemade weatherproof gland covered in a plastic gland shroud – it is essential to use the correct fittings in order to minimise corrosion of the cable armouring. Also, if the adaptable box is painted, you should clean off the paint where the cable enters it, to ensure good metal-to-metal contact and so effectively earth the armouring.
  • When connecting the cable to the lights, pay particular attention to the earth connections and any waterproof seals; it is vital that the units are weatherproof. You may also need glands to protect the SWA as it enters the lights – refer to the manufacturer's instructions.

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Low-voltage garden lighting

When it comes to garden lighting, a low-voltage set-up is the simplest to install and the safest. Often the light units are on spikes, which are simply pushed into the ground. The lights take their power from the transformer via ordinary two-core cable.

Running the cable

The lights are fed by a 12 volt transformer, which can be plugged into a convenient socket indoors or in a shed or garage – it must be protected from the weather. The cable size depends on the circuit length and load. It can be passed through a hole drilled in the wall and lined with conduit, or through a hole in a door or window frame. Plug the hole with silicone sealant to keep moisture at bay. Because of the low voltage, the cable can be safely laid on or just below the surface. But to avoid the trip hazard of loose cable, not to mention the sheer inconvenience of putting a garden spade through it at some future date, it is better to bury it about 450mm deep. Lay electrical route marker tape above it at a depth of about 150mm to indicate its presence.

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