Recessed Lighting Installation with Hole Cutting

For each light point, an electrician usually works in this order:

1. Switch off the circuit breaker for the lighting circuit and use a voltage tester to confirm the wires are dead.
2. Mark the centre of each hole from the layout plan. With several lights, use a tape measure or a cross-line laser so the rows come out straight.
3. Check that there is no metal ceiling profile, cable, pipe or ventilation duct where the hole will go.
4. Cut the hole with a plasterboard hole saw in the diameter given by the light manufacturer.
5. Pull the supply cable out from the void above the ceiling and check its condition.
6. Connect the wires to the terminal block or the driver as shown in the manufacturer's diagram.
7. Place the driver and connections in the ceiling void so they do not sit directly on the light.
8. Push the light into the hole and let the spring clips seat against the ceiling.
9. Switch the breaker back on and test the light, including the full dimming range if there is a dimmer.

Most modern installations use the standard colour code: blue is neutral (N), brown, black or grey is line (L) and green and yellow is earth (PE). Older installations may use different colours, which is one more reason to test rather than guess. Many LED downlights with a separate driver are double insulated and have no earth connection. In that case the electrician terminates the earth wire safely in a connector instead of leaving it loose.

LED downlights have practically replaced halogen ones. They use far less energy, run cooler and last much longer. When choosing, it pays to look at these features:

• Fixed or adjustable: fixed lights shine straight down, adjustable ones can be aimed at a picture or a worktop
• Integrated LED or replaceable lamp: integrated lights are usually slimmer, while with a replaceable lamp (such as GU10) you only change the bulb when it fails
• Installation depth: the gap between the plasterboard and the structural ceiling must be deep enough for the light and its driver
• IP rating: in a bathroom the required protection against moisture depends on the distance from the bath or shower, and above a shower IP44 or higher is a common choice
• Colour temperature: warm white (roughly up to 3000 K) suits bedrooms and living rooms, neutral white suits work areas
• Colour rendering (CRI): at least 80, and ideally around 90 in kitchens and bathrooms so food and skin do not look grey
• Dimming: the light, the driver and the dimmer must all be compatible with each other
• Fire rating: where the ceiling acts as a fire barrier, for example between flats, fire-rated downlights may be required

Why not just buy any downlight? Because the spacing between lights depends on the beam angle and the ceiling height. In a room of normal height, spacing is often roughly 0.6 to 1 m. A narrow beam needs the lights closer together, otherwise you get bright circles on the floor with darker strips between them.

The simplest case is a new ceiling where the electrician left a cable with some slack at every light position before the boards went up. Then fitting is quick and clean. It takes more work when:

• Cables have to be fished through above a finished ceiling, or a new lighting circuit is needed
• The ceiling has two layers of board or closely spaced profiles
• There is thermal insulation above the ceiling and it has to be kept clear of the light, or a light rated for contact with insulation is needed
• The ceiling is high and the work has to be done from a scaffold tower
• An older property has aluminium or deteriorated wiring
• The new light does not fit the hole left by an old one

A big advantage of a suspended ceiling is that cables can run in the void above it, often in flexible conduit, without chasing into walls. The cables still need to be fixed in place, not just laid loose on top of the plasterboard.

In practice, the same problems come up again and again:

• A hole is off line and the row of lights looks crooked
• The wrong hole saw size is used, and the clips cannot hold the light in an oversized hole
• The plasterboard cracks because too much pressure was put on the drill
• A cable gets hit while drilling because the circuit was not switched off
• The LED driver sits on insulation or on the light itself and overheats
• Connections are just wrapped in tape instead of using proper connectors
• The dimmer is not compatible, so the light flickers or buzzes

If a hole turns out too large, a decorative trim ring can cover the edge. Another option is to fill the hole with plaster filler and cut it again once it has set. A hole that is too small can be enlarged with a hole saw, as long as it is held exactly square to the ceiling. When replacing halogen downlights, measure the old holes first and look for LED lights with the same or a slightly larger cut-out.

It looks simple, but it is work on the fixed electrical installation. In most countries this kind of work must be done by a qualified electrician, and some types of work, such as new circuits or work in bathrooms, may need to be notified or certified under local building regulations. Check the rules with your local building authority. A wiring fault can cause a short circuit, an electric shock or a fire, and in the closed space above a ceiling you may not notice it straight away. For this reason there is no DIY guide for this job.

An electrician will also check whether the circuit can take extra lights, whether bathroom lights have the right IP rating and RCD protection, and whether the new installation needs inspection and testing with a certificate. If you live in a block of flats and the work would affect shared wiring, speak to the building management or owners' association first.

At handover, it is worth going through these points:

• All lights work and each switch controls the right group of lights
• When dimmed, the lights do not flicker or buzz
• The lights sit in straight lines at even distances from the walls
• The rims sit flat against the ceiling with no broken plasterboard visible around them
• A light does not move or drop out when pressed gently
• The colour of light is the same at every point
• Bathroom lights have an IP rating suitable for their zone
• You have the instructions, product details and, for new work, the test certificate