How to Plan Recessed Lighting: Spacing, Layout & Lumen Guide
Verthara's recessed lighting planning guide gives you the specific numbers — spacing, lumen targets, and layout formulas — that most lighting guides skip over. Planning recessed lighting badly is one of the most common UK renovation mistakes: too few fittings, poor spacing, or wrong wattage per room are fixable on paper but expensive after the plasterer has finished. This guide gives you the numbers to get it right first time.
What is the correct spacing for recessed downlights?
The 90–100cm spacing rule is based on beam angle and ceiling height. A standard 5W GU10 LED with a 36° beam angle produces a cone of light approximately 90cm in diameter at floor level from a 2.4m ceiling. Space the fittings so adjacent light cones just overlap at floor level — this eliminates dark patches between fittings.
The wall offset rule: position the first row of downlights 60cm from the wall. Less than 60cm creates scalloping — visible semicircles of light on the walls. More than 60cm leaves the wall perimeter dim. In narrow rooms (under 2.4m wide), a single central row may be more practical than two offset rows — adjust accordingly.
| Ceiling height | Recommended spacing | Wall offset |
|---|---|---|
| 2.4m (standard UK) | 90–100cm | 60cm |
| 2.7m (Victorian/Edwardian ground floor) | 100–120cm | 70cm |
| 3.0m+ (period property first floor) | 120–140cm | 75–80cm |
How many lumens does each room need?
Lumen targets by room type for UK homes:
| Room | Lumens per m² | Notes |
|---|---|---|
| Kitchen (general) | 400–500 lm/m² | Plus dedicated under-cabinet task lighting |
| Living room | 300–400 lm/m² | Supplement with table/floor lamps for ambience |
| Bedroom | 200–300 lm/m² | Plus bedside lamps. Dimmer essential. |
| Bathroom | 300–500 lm/m² | IP44/IP65 mandatory; add mirror task light |
| Hallway | 300–400 lm/m² | Safety-focused; no dimmer necessary |
| Home office | 400–500 lm/m² | Avoid glare on screens; use 4,000K colour temp |
Step-by-step recessed lighting layout plan
Step 1 — Measure the room: Get accurate room dimensions. For irregular rooms, break them into rectangles and plan each section independently.
Step 2 — Calculate total lumens: Multiply room area (m²) × target lm/m² for the room type. Example: 15m² kitchen × 450 lm/m² = 6,750 lumens needed.
Step 3 — Choose fitting and wattage: A 5W GU10 LED gives 450 lumens. 6,750 ÷ 450 = 15 fittings. Round to the nearest even number for symmetrical layouts: 16 fittings.
Step 4 — Draw the grid: On a scale plan, mark walls and place the first row 60cm from the wall. Space subsequent rows 90–100cm apart. Adjust to ensure even distribution across the room — slight adjustments of ±5–10cm per fitting won't affect light output noticeably.
Step 5 — Check circuit load: 16 × 5W GU10 = 80W total load on the circuit. A standard 6A MCB handles up to 1,440W — easily sufficient. For larger installations (commercial or whole-floor residential), check against the MCB rating before planning the circuit.
Step 6 — Dimmer sizing: If fitting a dimmer switch, confirm the dimmer's minimum and maximum load range. Most trailing-edge LED dimmers (the correct type for LED loads) have a minimum load of 10W — easily met by 16 × 5W fittings. Check the dimmer is rated for the total wattage of the circuit.
Kitchen-specific recessed lighting planning
UK kitchens need two layers of lighting: ambient (ceiling downlights) and task (under-cabinet lights over worktops). The ceiling downlights should not be positioned directly above the worktop — they create shadows from the overhead cabinets exactly where you're working. Position them in front of (room-side of) the overhead cabinets, so the beam angle clears the cabinet underside and lands on the worktop.
For a standard UK galley kitchen (2.4m × 3.6m), 8 × 5W GU10 downlights in two rows gives 3,600 lumens ambient, supplemented by under-cabinet LED strip lights for the worktop task areas.
Common mistakes when planning recessed lighting
Spacing downlights too far apart
Fittings spaced 120–150cm apart at a 2.4m ceiling leave visible dark patches. It's surprisingly easy to miscalculate — each extra 10cm of spacing per fitting reduces coverage overlap significantly. Fix: use the 90–100cm rule and stick to it.
Placing kitchen downlights above overhead cabinets
This position puts the beam behind the cabinet from the cook's perspective, creating a shadow on the worktop. Fix: place kitchen ceiling downlights 20–30cm out from the front face of overhead cabinets.
Not fitting dimmers in bedrooms and living rooms
Full-brightness recessed lighting in a bedroom at 10pm is unpleasant. Fix: always fit dimmers (trailing-edge, LED-compatible) in bedrooms and living rooms. The dimmer switch costs £15–£35 — much cheaper than rewiring after plastering.
Forgetting to specify fire-rated downlights in multi-storey properties
Using standard (non-fire-rated) downlights in any ceiling between habitable floors breaches Approved Document B. Fix: always specify fire-rated (FR) downlights as default; only use non-FR fittings in single-storey areas where confirmed safe.
Frequently asked questions
How far apart should recessed downlights be in a kitchen?
90–100cm apart and 60cm from the walls for a 2.4m ceiling height. For a standard UK kitchen of 12–18m², this typically means 8–16 × 5W GU10 fittings for adequate ambient lighting. Position them room-side of overhead cabinets (not directly above) to avoid worktop shadows.
How many recessed lights do I need for a 15m² room?
For a living room at 350 lm/m², you need 5,250 lumens. At 450 lm per 5W GU10, that's 11–12 fittings. For a kitchen at 450 lm/m², you need 6,750 lumens — 14–16 fittings. Round up to the nearest even number for symmetrical placement.
What happens if downlights are too close together?
Spacing under 60cm creates obvious hotspots — bright circles overlapping on the ceiling and floor with visible, harsh transitions. The room looks commercial rather than domestic. Fix: maintain 90cm minimum spacing for a residential downlight installation.
Should I use 5W or 7W GU10 bulbs?
5W (400–500 lm) is standard for ambient lighting. 7W (600–700 lm) is appropriate for task-intensive areas or rooms with higher lumen targets. Using 7W throughout reduces the number of fittings needed (saving installation cost) but creates a brighter, less flexible result — harder to dim to a low level without noticeable flicker.
What colour temperature is best for kitchen recessed lighting?
4,000K (neutral white) is the best choice for UK kitchen ambient lighting — it gives accurate colour rendering for food preparation without the clinical harshness of 6,500K. 3,000K works in kitchens with a warm, domestic feel but may make food appear slightly yellowish under direct light.
Does Verthara offer help with recessed lighting planning?
Verthara provides detailed product specifications including beam angles, lumen outputs, and ceiling void depth requirements for all recessed downlights. Our editorial guides cover layout planning in depth. All orders come with free UK delivery and a 3-year manufacturer warranty, with same-day dispatch for orders placed before 12pm GMT.