Here is how you install downlights: isolate the circuit, mark out the positions, cut the holes about 3 mm wider than the cut-out size on the packaging, wire the fittings in parallel with lever connectors, and click them in on their spring clips.
Sounds simple, and in a plasterboard or suspended ceiling it usually is. The sting is in the detail: the right cut-out size, enough room above the ceiling, the correct IP rating in the bathroom, and a dimmer that actually suits your driver.
In this article I walk you through the whole job. From tools and measurements to wiring, working out how many downlights you need, and the costs. So you do not have to click any further after reading this.
What do you need to install downlights?
The job itself takes very little kit. This is your basic list:
- Cordless drill
- Hole saw in the right diameter (or a jigsaw for plasterboard)
- Compass and pencil for marking out
- Voltage tester (essential, more on that shortly)
- Cable and stud detector to check what runs above the ceiling
- Lever connectors (Wago type) or terminal blocks
- Wire strippers and possibly a screwdriver
- Safety glasses and a dust mask
For a concrete ceiling, add a hammer drill or SDS drill with a diamond core bit. More on that further down.
What cut-out size do you need?
Two terms get mixed up constantly, but they mean different things.
The cut-out size is the diameter of the hole the fitting needs. It is always printed on the packaging. The outside diameter is the visible bezel that sits over the hole and covers it neatly.
Common cut-out sizes for modern LED downlights are 50, 60, 68, 70, 75 and 80 mm, with 68 to 75 mm being the most widely used (source: pretmetled.nl, ledspot-planet.com). The classic downlight standard is 68 mm.
Rule of thumb for cutting: make the hole about 3 mm wider than the cut-out size on the packaging (source: DIY chains Gamma and Hubo). The fitting then clicks in smoothly without the spring clips binding, and the bezel still covers the hole neatly.
Cut the hole too big by accident? A gap of 1 to 2 cm can usually be rescued with a conversion ring, as long as the outside diameter still covers the opening (source: ledspot-planet.com).
How much recess depth do you need above the ceiling?
This is the measurement people overlook most often. Above the ceiling the fitting has to physically fit, plus the driver, plus a bit of air to shed heat.
Recess depth ranges from around 23 to 25 mm for ultra-slim LED downlights up to 8 to 10 cm for traditional models (source: ledspot-planet.com). For a standard LED downlight, allow at least 5 to 10 cm of clear space above the ceiling. For an ultra-slim fitting, 3 to 4 cm is often enough.
Important: with a 230V GU10 fitting, count the height of the lamp plus the GU10 holder as well. That is a classic slip-up that leaves the fitting just short of fitting (source: ledspot-planet.com).
Leave at least 1 cm of clearance
all around for cooling. Pushing a downlight hard against a joist, a pipe or insulation is asking for overheating and a shorter life.
230V GU10 or 12V MR16: which type do you pick?
Two different worlds, and it pays to decide up front.
230V with a GU10 holder runs straight off mains voltage. No transformer needed, you simply loop the fittings into the existing lighting circuit. For most ceilings in a house this is the easiest and most popular route.
12V with an MR16 holder runs on extra-low voltage and needs a transformer or LED driver to step 230V down to 12V. More links in the chain, more that can fail, but sometimes handy in very shallow recesses or with specific fittings.
For DIY in an ordinary ceiling, 230V GU10 is generally the sensible choice. If you do go for 12V, watch the capacity of your driver.
| Feature | 230V GU10 | 12V MR16 |
|---|---|---|
| Transformer/driver needed | No | Yes |
| Wiring | Loop straight through | Via driver |
| Prone to faults | Less so | More links |
| Typical use | Standard ceiling | Shallow/special recess |
Dimming, colour temperature and brightness
If you want to dim, three things need to line up: the fitting is dimmable, the dimmer suits the type of LED, and the dimmer reaches its minimum load.
Watch the dimming technology. For LED you normally want a trailing edge dimmer, marked with an RC or R,L,C symbol. An old leading edge dimmer often makes LEDs flicker.
Two pitfalls when dimming LED:
- Minimum load. Many dimmers have a lower limit (3 to 10 W, for example). Connect too little wattage and the light flickers. Check your dimmer’s data sheet.
- Number of downlights per dimmer. That depends on the combined wattage of your fittings versus the dimmer’s maximum load. Just do the sum: 8 fittings at 5 W is 40 W, comfortably inside a dimmer rated for 100 or 200 W of LED.
Colour temperature sets the mood:
- 2700K: warm white, cosy, for living rooms and bedrooms
- 3000K: warm-neutral, widely used in kitchens and hallways
- 4000K: neutral white, functional, for bathrooms, home offices and garages
Beam angle sets the spread. A narrow beam (around 24 to 38 degrees) accents, a wide beam (60 degrees or more) fills the room more evenly. For general ceiling lighting you usually go wide.
How many downlights do you need?
Two things come together here: enough light (lumens) and a tidy layout (spacing).
Light per room. A workable rule of thumb for general lighting (source: various lighting specialists):
| Room | Lumens per m² (general) |
|---|---|
| Living room / bedroom | 100 to 150 |
| Kitchen (general) | 300 to 500 |
| Bathroom (general) | 150 to 200 |
Over a worktop you want considerably more, in the region of 2000 to 4000 lumens of directed light, and at the bathroom mirror 300 to 500 lumens per m².
Worked example: a 20 m² living room wants roughly 20 x 125 = 2500 lumens of general light. An LED downlight of around 400 lumens means about 6 fittings for the base layer, topped up with mood or reading light where you want it.
Spacing. Keep it simple:
- At least 30 to 35 cm between fittings (source: Gamma, Hubo)
- 40 to 50 cm from the wall at a standard ceiling height of 2.4 to 2.6 m, otherwise you get scallops of light on the wall (source: Hubo, pretmetled.nl)
- Over a kitchen run, closer to the wall instead, around 30 cm, so the light lands on the worktop
- Do not tilt adjustable fittings more than about 30 degrees, beyond that the beam partly hits the inside of the fitting (source: pretmetled.nl)
Draw the pattern on paper first, or mark it out on the ceiling with tape. An even grid looks calm. Downlights scattered without thought stand out immediately.
IP rating and bathroom zones: this part is not optional
In a wet room the requirements are hard rules. Water and 230V do not mix, and the wiring regulations set a minimum IP rating for each zone.
The IP code tells you about resistance to dust and water. In a bathroom the second digit (water) is what matters most: IP44 is splash-proof, IP65 keeps out direct water jets.
The bathroom zones follow the harmonised IEC 60364-7-701 framework, applied as BS 7671 Section 701 in the UK and NEN 1010 in the Netherlands (source: various electrical trade sources, including flinkelektro.nl and ledspot-planet.com):
| Zone | Where | Minimum IP rating |
|---|---|---|
| Zone 0 | Inside the bath or shower tray | IPX7 (special fittings) |
| Zone 1 | Directly above bath or shower up to 2.25 m | IP65 |
| Zone 2 | Up to 60 cm around zone 1 | IP44 |
| Zone 3 | Outside that | IP44 recommended |
In short: directly above the shower or the bath you want IP65 as a minimum, and IP44 as a minimum in the zone around it. Unsure about how the zones fall, or about earthing, bonding and RCD protection in the bathroom? That is exactly the moment to bring in a registered electrician. In a bathroom, the consequences of a mistake are serious.
Fire-rated and insulation-coverable fittings: the forgotten pitfall
Plenty of guides skip this point, and it genuinely matters.
If there is insulation above your ceiling (think of a ceiling under a roof or a loft), you cannot simply drop in an ordinary downlight. A standard fitting needs to shed its heat into the air around it. Push insulation over the top and the heat builds up.
Two consequences: the fitting fails far sooner, and in the worst case you create a fire risk.
The answer is a fitting that is rated to be covered with insulation, usually described as insulation-coverable, IC-rated or fire-rated. These fittings carry a specific symbol to show it. Cannot keep the insulation away from the fitting? Then always choose that type, or create a clear, fire-safe pocket around the fitting.
Sort this out before you cut, not afterwards.
Wiring: looping in and connecting in parallel
The electrical side is the bit most people find nerve-racking. Take it steady, it is very doable once you understand the basics.
You spur off an existing lighting point or the lighting circuit, and connect the fittings to each other by looping in: the cable runs on from fitting to fitting. What matters here:
- Parallel, not in series. Every fitting gets both live and neutral. In series the voltage would be shared out and nothing works properly (source: getled.nl).
- Lever connectors or terminal blocks. Lever connectors are quicker and more reliable when clamping several conductors. Terminal blocks work too, as long as they are done up tight.
- Earthing. Metal fittings and bathroom zones need the earth conductor connected. Terminate it properly wherever it is present.
Circuit load. With LED you rarely get anywhere near the limit. A 16A lighting circuit handles up to roughly 3500 W, and 20 LED downlights at 5 W come to only about 100 W in total (source: getled.nl). So the limiting factor is almost always your dimmer, not the circuit.
If you are working with 12V fittings, the capacity of the driver or transformer is the limit. Add up the wattage of your fittings and stay under the driver’s maximum load, with some headroom. With a classic transformer you look at VA, with a modern LED driver at watts.
Plasterboard, concrete or timber: different approaches
The ceiling type dictates your tools and your method.
Plasterboard or a suspended grid ceiling. The easiest situation. An ordinary hole saw or even a jigsaw does the job, and the spring clips grip nicely behind the board. Most DIY downlights are made for exactly this.
Concrete ceiling. Here you need a hammer drill or SDS drill with a diamond core bit, and it is heavy, dusty work. Standard spring clips do not hold well in solid concrete, so choose fittings with leaf springs or go for a surface-mounted solution (source: ledspot-planet.com). With concrete, a dropped ceiling or a track of spots is often more practical than drilling straight into the slab.
Timber ceiling or cladding. Easy to work with, but pay extra attention to fire safety and to the clear space above. Timber and trapped heat are not a happy combination, so cooling and possibly an insulation-coverable fitting matter here.
Step by step: installing downlights
- Isolate the circuit. Switch off the right circuit at the consumer unit. Then check with a voltage tester that the supply really is dead. This is not optional.
- Check what sits above the ceiling. Use a cable and stud detector to trace cables and joists before you drill.
- Mark out the positions. Set out your grid with pencil and compass, and stick to the spacing (30 to 35 cm between fittings, 40 to 50 cm from the wall).
- Cut the holes. Drill a small pilot hole first if it helps, then cut with the hole saw about 3 mm wider than the cut-out size. Glasses and dust mask on.
- Run the cable. Loop the cable from fitting to fitting, wired in parallel. Leave enough slack to make the connections comfortably.
- Connect the fittings. Join live, neutral and (where needed) earth with lever connectors or terminal blocks. With 12V, connect the driver first.
- Click the fittings in. Squeeze the spring clips inwards, push the fitting into the hole and let go. The clips pull it up tight against the ceiling.
- Switch on and test. Restore the circuit and check that everything lights up and, if dimmable, dims smoothly without flicker.
Common mistakes when installing downlights
- Not checking with a voltage tester. Switching off the circuit alone is not enough, always verify.
- Allowing too little recess depth, so the fitting plus lamp holder just will not go in.
- Pressing the fitting hard against insulation or a joist, causing overheating.
- Choosing an IP rating that is too low for the bathroom zone.
- Reusing an old leading edge dimmer with LED, and getting flicker as a result.
- Staying below the dimmer’s minimum load, so the light blinks.
- Drilling without checking for cables first.
- Not using an insulation-coverable (fire-rated) fitting where there is insulation above the ceiling.
What does it cost to install downlights?
Prices move around, so work with ranges. The figures below are indicative and vary by country and retailer.
| Item | Realistic range |
|---|---|
| Single LED downlight (GU10, dimmable) | approx. 8 to 25 euros each |
| Set of 6 fittings including lamps | approx. 50 to 120 euros |
| Hole saw in the right size | approx. 10 to 25 euros |
| LED dimmer (trailing edge) | approx. 25 to 60 euros |
Doing it yourself, a set of 6 fittings including tools and a dimmer usually keeps you under 150 to 250 euros. Have an electrician fit and connect them and you add labour on top of the materials, which varies a lot with complexity (creating a new lighting point, bathroom, concrete). Always get a quote first.
The biggest saving from doing it yourself is the labour. The biggest reason to hand it over is the bathroom, and any situation where a new circuit or connection is needed.
When should you call in a registered electrician?
Rules on DIY electrical work differ by country, so check what applies where you live. In England and Wales, work in a bathroom counts as notifiable under Part P of the Building Regulations, which means it has to be certified by a registered electrician or signed off by building control. Adding fittings to an existing lighting circuit elsewhere in the house is generally not notifiable, but it still has to comply with BS 7671. Either way, you are responsible for a safe installation.
Bring in a registered electrician if:
- You need a new circuit or a new spur point
- It involves the bathroom and you are unsure about zones, earthing, bonding or RCD protection
- You are working in concrete or a structurally awkward situation
- You feel uncertain about the connection at any point
Better to have it checked once than to leave an unsafe situation sitting in your ceiling.
Frequently asked questions
How big should the hole for a downlight be?
Cut the hole about 3 mm wider than the cut-out size printed on the packaging. Common cut-out sizes run from 50 to 80 mm, with 68 to 75 mm the most usual.
How much space do I need above the ceiling?
For a standard LED downlight, allow 5 to 10 cm of clear space, and for an ultra-slim fitting often 3 to 4 cm. With 230V, count the height of the lamp plus the GU10 holder, and leave at least 1 cm all around for cooling.
How many downlights do I need per m²?
Work from lumens: a living room wants roughly 100 to 150 lumens per m² of general light, a kitchen 300 to 500. Divide that by the lumens per fitting. Keep 30 to 35 cm between fittings and 40 to 50 cm from the wall.
What IP rating does a bathroom downlight need?
Directly above a bath or shower (zone 1) IP65 as a minimum, and in the zone up to 60 cm around it (zone 2) IP44 as a minimum, in line with the wiring regulations.
Can I install downlights myself without an electrician?
In a plasterboard or suspended ceiling, spurring off an existing lighting point, this is well within DIY reach as long as you isolate the circuit and verify it is dead. For a bathroom, a new circuit or concrete, a registered electrician is the sensible call, and in England and Wales bathroom work has to be certified.
Why do my LED downlights flicker when I dim them?
Usually the dimmer is wrong for the job. LED needs a trailing edge dimmer, and you have to stay above the dimmer’s minimum load. Too little wattage or an old leading edge dimmer gives you flicker.
Get stuck in
Downlights are one of those jobs that make a house feel finished straight away. As long as your measurements are right, the circuit is isolated and the bathroom gets the correct IP rating, you can get a long way yourself.
Working on a bigger ceiling or finishing project, such as a suspended ceiling, new partition walls or fitting out a whole room? In Fred’s DIY Handbook I explain interior jobs step by step, from walls and ceilings through to the finishing. Handy for pulling your lighting into the bigger picture from the start.
Good luck with the job. Measure twice, cut once.