Garden lighting

1. 1

   Plan the layers

   Decide the path, task, feature and ambient lighting before buying anything, and light surfaces rather than eyes.

2. 2

   Choose the voltage

   Use a low voltage 12 V system where you can, because the cable does not need the same burial protection as mains.

3. 3

   Size the transformer

   Add up the fitting wattage and allow 20 percent headroom, keeping cable runs short to avoid voltage drop at the far end.

4. 4

   Dig the cable routes

   Bury mains armoured cable at 450 mm or more with warning tape above, and run low voltage cable in conduit under planting.

5. 5

   Fit the lights

   Set spikes and recessed fittings before the surface finishes go down, aiming and shielding each one to avoid glare.

6. 6

   Commission and control

   Test the whole circuit, set the timer or photocell, and have any mains work certified by a qualified electrician.

• Fixed garden lighting wiring is notifiable work in some circumstances under Part P, particularly anything wired off the mains in a special location. ^[1]
• All outdoor electrical installations must comply with BS 7671, including correct RCD protection and IP-rated fittings. ^[2]
• Light spill that disturbs neighbours can be a statutory nuisance under the Clean Neighbourhoods and Environment Act 2005. ^[3]

• Before trenching any garden lighting cable, CAT & Genny sweep along the run (HSE HSG47). Spike-light supply trenches are shallow and cross everything. Full method in the Safety guide.
• Use SELV 12 V for spike, deck and step lights, safer in wet ground and homeowner-installable.
• Aim for 2700–3000 K (warm white) outdoors. Anything cooler reads as 'car park'.
• IP65 minimum for exposed fittings; IP67 for in-ground uplighters and pond lights.
• Position lights to graze textures (walls, bark) rather than point upward into eyes or windows.

Good garden lighting is not more light, it is fewer, better-placed fittings. Work in three layers and you get depth after dark instead of a floodlit lawn.

• Layer one, movement and safety: steps, level changes, thresholds and the path from the gate to the door. Low output, shielded, aimed down. Recessed step lights or low bollards beat a bright wall pack every time.
• Layer two, structure: uplight two or three trees, a wall texture or a specimen shrub. Narrow beams of around 15 to 24 degrees for tall trees, 36 to 60 degrees for shrubs and wall washes.
• Layer three, atmosphere: festoon over a seating area, a warm glow in a planter, a single downlight over the outdoor table. This is the layer people actually switch on most nights.
• Use one circuit per layer, or a smart driver with scenes, so you are not forced to run the whole garden at full output to read a book on the patio.
• Aim fittings away from windows, both yours and next door's. If you can see the lamp itself from a seating position, add a snoot, a louvre or move it.
• Dark-sky good practice: point light down where you can, shield anything pointing up, and put everything on a timer that goes off around midnight. It protects wildlife and keeps neighbours friendly.

• Size the transformer to no more than 80 percent of its rated load, so a 100 W driver carries about 80 W of fittings. Overloaded drivers are the most common early failure.
• Voltage drop is what makes the far end of a 12 V run look dim. Keep runs under about 20 m in 2.5 mm2 cable, or split into two runs from a central point.
• Bury SELV cable at least 300 mm deep in a garden, in a duct or with warning tape above it, so the next person planting a shrub finds tape rather than the cable.
• Mains cable outdoors is SWA armoured cable, buried at least 450 mm in soft ground and 600 mm under a drive, terminated in an IP-rated gland. This is electrician work and may be notifiable under Part P.
• Every outdoor circuit needs 30 mA RCD protection at the consumer unit, without exception.
• Use gel-filled or resin connectors for every buried joint. Terminal blocks in a plastic box fill with water within a winter.

• Quality 12 V SELV spike or uplight fittings: around £40 to £120 each. Sub-£20 fittings usually fail within two winters because the seal and the driver are the parts that were cut.
• Transformer or driver: £60 to £180 depending on wattage and whether it is smart-controlled.
• Installed cost for a typical small garden scheme of 8 to 12 fittings with trenching and controls: roughly £900 to £2,000.
• Adding a mains SWA supply and an outdoor socket to serve the far end of the garden: typically £400 to £900 including certification.
• Running cost is negligible: 12 LED fittings at 4 W each on 5 hours a night is about 9 kWh a month.

• Too many fittings at equal spacing. A line of identical spikes down a path reads like an airport runway; light fewer things properly and leave gaps of darkness in between.
• Cool white lamps outdoors. Anything over about 3000 K makes planting look grey and the garden feel like a car park.
• Uplighting straight into a window or a neighbour's bedroom. Angle across the object, use a shield or a narrower beam, and check the view from the house at night.
• Undersized cable on a long 12 V run. Voltage drop dims the far fittings and the usual response, a bigger transformer, only makes it worse.
• Burying cable shallow and unmarked. 300 mm minimum for SELV in a duct with warning tape, 450 mm for armoured mains cable.
• Terminal blocks in a plastic box as a buried joint. Use gel or resin connectors; anything else fills with water in one winter.
• Fitting everything to one switch. Without layers or scenes you either flood the whole garden or leave it dark.