Extension Lighting Design: Complete Guide
How to maximise natural light, plan artificial lighting, and create the perfect atmosphere in your new extension.
TL;DR - The Quick Answer
Good extension lighting combines natural light strategies - rooflights cost £800-£2,500 each, clerestory windows suit side returns - with three artificial layers: ambient (150-300 lux), task (300-500 lux), and accent. Kitchens need 4000K LEDs with CRI 90+ and under-cabinet task lighting; living spaces suit 2700-3000K with dimmable circuits. Space downlights 1-1.2m apart. Plan everything during electrical first fix - adding recessed lights after plastering is costly.
Lighting can make or break an extension. Get it right and you'll have a bright, welcoming space that works day and night. Get it wrong and you'll struggle with dark corners, harsh glare, and an uncomfortable atmosphere. Plan your lighting before construction begins.
Maximising Natural Light
Natural light should be your starting point. The right glazing strategy reduces reliance on artificial lighting and creates a connection to outdoors.
Rooflights & Skylights
- Bring light deep into the extension
- Position away from southern exposure to reduce overheating
- Cost: £800-£2,500 per rooflight including installation
Bi-fold & Sliding Doors
- Large glazed doors flood the space with light
- Consider solar control glass for south-facing installations
- Part O may limit glazing area in some cases
Clerestory Windows
- High-level windows bring light without compromising privacy
- Free up wall space for furniture below
- Ideal for side return extensions
Artificial Lighting Layers
Good lighting design uses three layers working together. Each serves a different purpose.
| Layer | Purpose | Lux Level |
|---|---|---|
| Ambient | General background light from downlights, pendants, or indirect lighting | 150-300 lux |
| Task | Focused light for activities - under-cabinet lighting, desk lamps | 300-500 lux |
| Accent | Decorative highlights - picture lights, LED strips, feature pendants | Variable |
| Room Type | Colour Temp | Key Fittings | Notes |
|---|---|---|---|
| Kitchen | 4000K | Downlights, under-cabinet LEDs, island pendants | CRI 90+ for food prep; separate circuits |
| Living/Dining | 2700–3000K | Dimmable downlights, statement pendant, wall lights | Multiple circuits for mood control |
| Extension (general) | 2700–4000K | Rooflights (£800–£2,500 each), bi-folds, clerestory | Plan during electrical first fix |
Source: Mayfair Studio project data • Data as of 2025
Room-by-Room Guidance
Kitchen Extension
- Under-cabinet task lighting essential
- Pendants over islands/breakfast bars
- Downlights on separate circuits for flexibility
- Consider 4000K colour temperature for food preparation
Living/Dining Extension
- Multiple circuits for different moods
- Dimmable downlights, statement pendant over dining table
- Wall lights or floor lamps for evening ambiance
- 2700-3000K for warmth and relaxation
LED Specifications
Choosing the right LEDs makes a huge difference to atmosphere and usability.
Key Specifications to Consider
- Colour temperature: 2700K (warm) to 4000K (cool white)
- CRI (colour rendering): 90+ for kitchens and living areas
- Dimming: LED-compatible dimmers essential
- IP rating (bathrooms): IP44 minimum, IP65 for zone 1
Good extension lighting uses three layers - ambient (150–300 lux), task (300–500 lux), and accent. Rooflights cost £800–£2,500 each and are the best way to bring daylight into a deep extension. Plan all recessed downlights during electrical first fix: adding them after plastering is expensive and disruptive.
Frequently Asked Questions
Frequently Asked Questions
How many downlights do I need?
Rule of thumb: one downlight per 1.5 sqm. Space 1-1.2m apart, 60cm from walls. Adjust based on ceiling height and desired brightness.
Can I add lights later?
Surface-mounted or plug-in lights yes. Recessed lights and new circuits are expensive after plastering. Plan generously during first fix.
What about smart lighting?
Smart switches or bulbs can be added later. For built-in smart systems, plan during electrical first fix. Ensure neutral wire is run to all switches.