Rooflights are one of the most effective ways to bring natural light into a rear extension or converted space. A well-positioned rooflight changes the character of a room entirely — particularly in north-facing or enclosed spaces where side windows provide limited light. They are also one of the components most often under-specified: a cheap rooflight that leaks, condenses internally, or fails within a few years is a disproportionately expensive problem to fix when it's embedded in a finished roof.
Rooflight Types
Pitched roof skylights sit within the plane of a pitched roof. Velux is the dominant brand in the UK and has an extensive range. Standard units are double-glazed with a U-value of 1.0–1.4 W/m²K; triple-glazed units achieve 0.7 W/m²K. Electrically operated venting units add passive ventilation; solar-powered versions require no cable routing.
Flat roof rooflights are typically upstand-mounted (the glazing unit sits proud of the roof on a kerb). Frameless glass-to-glass units (Hip roof, Roof Maker, IQ Glass) give a clean architectural appearance; aluminium-framed units are more affordable and almost as visually light. Minimum kerb upstand is 150mm to prevent water ingress — this is a building regulations requirement, not a suggestion.
Roof lanterns are multi-pane glazed structures on top of a flat roof, typically square or rectangular. They're more architectural and introduce more light but have more junctions and more opportunities for leakage — detailing and installation quality are critical.
Planning Rules
Skylights on pitched roofs generally fall within permitted development if they don't protrude more than 150mm above the roof plane and are not on the principal elevation facing a highway. Flat roof rooflights are treated similarly. However, listed buildings and properties in conservation areas require consent for any external alteration — check before ordering.
Glazing Specification
Building regulations require a minimum U-value of 1.6 W/m²K for rooflights (Part L). Laminated glass on the inner pane is essential for safety — a rooflight directly above a living area that fails catastrophically with standard toughened glass is dangerous. Most quality manufacturers supply this as standard; check the specification sheet before purchasing.
Costs
| Type | Supply cost | Installed cost |
|---|---|---|
| Velux pitched roof skylight (1m²) | £400–£800 | £700–£1,400 |
| Flat roof rooflight (1m²) | £600–£1,200 | £1,000–£2,000 |
| Roof lantern (2m x 1m) | £1,500–£4,000 | £2,500–£6,000 |