How to Plan Downlight Spacing for Any Room

Getting Downlight Spacing Right

Downlights are the go-to lighting choice for modern domestic refurbs. They give a clean, flush ceiling with even illumination — when they're positioned correctly. Get the spacing wrong and you end up with dark spots, bright patches, or a ceiling that looks like a Swiss cheese.

Here's how to plan a downlight layout that works.

The Basic Spacing Rule

The fundamental rule for downlight spacing is based on the beam angle of the fitting and the ceiling height:

Maximum spacing = Ceiling height × 0.7

For a standard 2.4m ceiling:

2.4 × 0.7 = 1.68m maximum spacing between lights

In practice, most installations use 1.2–1.5m spacing for even coverage. Going tighter than 1.2m is usually overkill unless you want a very bright room.

Distance from Walls

The first row of downlights should sit approximately half the spacing distance from the wall:

For 1.5m spacing: first row at 0.75m from the wall

This prevents the walls from looking dark while avoiding "wall washing" effects where the light cone hits the wall at an angle.

How Many Downlights Per Room?

A quick formula:

Number of downlights = Room area (m²) ÷ Spacing²

For a 4m × 3m room at 1.5m spacing:

12 ÷ (1.5 × 1.5) = 12 ÷ 2.25 = 5.3 — round up to 6

Then arrange them in a grid pattern. For this room, a 3 × 2 layout works well:

• 3 lights across the 4m wall at 1.33m centres
• 2 rows across the 3m dimension at 1.5m centres

The Downlight Calculator works out the optimal layout automatically. Enter your room dimensions and it gives you the number of lights and their positions.

Room-by-Room Guide

Kitchen

Kitchens need more light than other rooms — you're working with sharp tools and hot surfaces. Aim for 300–500 lux at worktop height.

| Kitchen Size | Number of Downlights | Suggested Layout | |---|---|---| | Small galley (2m × 3m) | 4 | 2 × 2 grid | | Medium (3m × 3m) | 6 | 2 × 3 grid | | Large (4m × 4m) | 9 | 3 × 3 grid | | Kitchen-diner (4m × 6m) | 12 | 3 × 4 grid |

Consider positioning a row of downlights directly above the worktop edge (about 600mm out from the wall) to illuminate the work surface without your body casting shadows.

Bathroom

Bathrooms need careful planning because of electrical zones as defined in BS 7671:

• Zone 0 (inside the bath/shower tray): IP67 rated, 12V max
• Zone 1 (above the bath/shower to 2.25m height): IP65 minimum, connected via 30mA RCD
• Zone 2 (0.6m beyond Zone 1): IP44 minimum

Most bathroom downlights are fire-rated and IP65 as standard. Budget 4–6 downlights for a standard bathroom (2m × 2.5m).

Living Room

Living rooms typically need 150–300 lux. Consider putting downlights on a dimmer — full brightness for reading, dimmed for watching TV.

| Room Size | Number of Downlights | Layout | |---|---|---| | Small (3m × 3m) | 4–6 | 2 × 2 or 2 × 3 | | Medium (4m × 4m) | 6–9 | 3 × 2 or 3 × 3 | | Large (5m × 5m) | 9–12 | 3 × 3 or 3 × 4 |

Bedroom

Bedrooms need less light — 100–200 lux is plenty. Over-lighting a bedroom makes it feel like an office.

| Room Size | Number of Downlights | |---|---| | Single (2.5m × 3m) | 4 | | Double (3m × 4m) | 4–6 | | Master (4m × 5m) | 6–8 |

Hallway

Hallways are narrow, so a single row down the centre usually works. Space them at 1.2–1.5m apart along the length.

| Hallway Length | Number of Downlights | |---|---| | Up to 3m | 2 | | 3–5m | 3 | | 5–8m | 4–5 |

Wattage and Brightness

LED downlights are rated in lumens (light output) and watts (power consumption). Here's how they compare to old halogen fittings:

| LED Wattage | Approximate Lumens | Halogen Equivalent | |---|---|---| | 4–5W | 350–450 lm | 35W GU10 | | 6–7W | 500–650 lm | 50W GU10 | | 8–10W | 700–900 lm | 75W halogen | | 12–15W | 1,000–1,200 lm | 100W halogen |

For most domestic rooms, 6–8W LED downlights (500–700 lumens each) are the sweet spot. Enough light for general use without being harsh.

Colour Temperature

| Kelvin (K) | Colour | Best For | |---|---|---| | 2700K | Warm white | Living rooms, bedrooms, dining rooms | | 3000K | Neutral warm | Kitchens, bathrooms, hallways | | 4000K | Cool white | Garages, utility rooms, offices |

Stick to one colour temperature throughout the house. Mixing warm and cool white in adjacent rooms looks odd, especially in open-plan spaces.

Fire-Rated Downlights

Building Regulations Part B (Fire Safety) requires downlights in ceilings that form part of a fire-resistant barrier to maintain the fire rating of the ceiling.

In practice, this means:

• Fire-rated downlights are required in almost all domestic ceilings — between floors, between a garage and habitable rooms, and in flats
• They typically provide 30-minute or 60-minute fire resistance through an intumescent pad that expands in heat and seals the hole
• Building control will check for fire-rated fittings at final inspection

Always specify fire-rated downlights for domestic work. The cost difference is minimal (£2–£4 more per fitting) and it avoids issues with building control. Non-fire-rated fittings are only suitable where the ceiling isn't a fire barrier (ground floor of a bungalow, for example).

Installation Considerations

Insulation Contact

If the ceiling has insulation above (loft insulation or between floors), the downlight must be rated for IC (Insulation Contact). Standard downlights overheat if insulation is packed around them.

Most modern fire-rated LED downlights are IC-rated as standard. Check the specification before buying.

Ceiling Void Depth

LED downlights need less depth than old halogen fittings, but still require adequate clearance:

| Fitting Type | Minimum Ceiling Void | |---|---| | Slim LED fixed | 40–60mm | | Standard LED adjustable | 70–100mm | | Fire-rated LED | 60–100mm |

Check the void depth before specifying fittings. Concrete soffits, steel beams, or services in the void can limit your options.

Circuit Design

Downlights are typically wired on a 6A lighting circuit in 1.0mm² or 1.5mm² twin and earth cable, as covered by the current IET BS 7671 guidance. A single circuit can handle up to about 10–12 LED downlights (at 8W each, that's only 96W — well within the 1,380W capacity of a 6A circuit).

For larger rooms or whole-floor installations, consider splitting across two circuits for resilience. If one circuit trips, you're not left entirely in the dark.

If you need to check cable sizes for the lighting circuit, the Cable Calculator handles BS7671 sizing for voltage drop and current capacity.

Dimming

Not all LED downlights are dimmable. If the customer wants dimmers (and most do), check that:

• The downlight is marked as dimmable
• The dimmer switch is LED-compatible (trailing edge or universal)
• The minimum load meets the dimmer's requirements (some dimmers need at least 25–40W total load to work properly with LEDs)

Old-style leading-edge dimmers cause LEDs to flicker, buzz, or fail to dim smoothly. Always specify a trailing-edge dimmer for LED circuits.

Common Mistakes

• Too many lights. More isn't better. A grid of 20 downlights in a 3 × 4m room looks industrial, generates too much heat, and wastes energy.
• Too close to the walls. Downlights within 300mm of a wall create a harsh "halo" effect and highlight every imperfection in the plaster.
• Ignoring the beam angle. A narrow beam angle (24°) creates defined pools of light — good for accent lighting but poor for general illumination. Use 38–60° beam angles for general room lighting.
• Mixing brands. Different LED manufacturers produce slightly different colour temperatures even at the same Kelvin rating. Buy all your fittings from one manufacturer for consistency.
• Cutting holes before planning. Mark out the full layout on the ceiling, check it looks balanced from below, and adjust before cutting. Moving a downlight hole means patching the ceiling.
• Forgetting about joists. Check joist positions before finalising your layout. You can't put a downlight where there's a joist.

Quick Summary

1. Space downlights at ceiling height × 0.7 (typically 1.2–1.5m for domestic)
2. First row at half the spacing distance from the wall
3. Use 6–8W LEDs for most domestic rooms (500–700 lumens each)
4. Always specify fire-rated, IC-rated fittings
5. Use LED-compatible trailing-edge dimmers
6. Check the layout against joist positions before cutting

The Downlight Calculator takes the guesswork out of layouts — enter your room dimensions and it gives you the number of lights and optimal grid positions.