What is the difference between a rooflight and a skylight?

These terms are often used interchangeably. A rooflight usually refers to a flat-roof-mounted unit (flush or slightly raised); a skylight often refers to units fitted into a pitched roof. Velux windows are technically rooflights for pitched roofs.

Does a skylight require planning permission?

A rooflight that doesn't protrude more than 150mm above the roof plane and is not on a front elevation is usually permitted development. Roof lanterns on extensions may require planning if they exceed certain heights.

Do skylights cause heat loss?

A quality triple-glazed rooflight or roof lantern has a U-value of 0.6–1.0 W/m²K, comparable to a good wall. Single glazed or low-spec units can cause significant heat loss. Always choose at least A-rated double glazing.

Extensions & Conversions · Last updated 19 October 2026

Skylight installation cost

Typical range£600–£12,000· Average flat roof skylight / rooflight installed

Fixed and opening skylight costs for 2025. In the UK, expect to pay between £600 and £12,000, with the typical project around £1,500 (average flat roof skylight / rooflight installed). Regional variation, specification tier and site access conditions all shift the final quote.

Quick answer: Skylight installation cost in the UK typically costs between £600 and £12,000 (Average flat roof skylight / rooflight installed). London and the South East run 20–35% above this range; the North, Wales and most of Scotland sit 5–15% below.

Homeowners researching this typically also price up velux window cost. For wider context, browse our bathroom pricing, kitchen pricing and boiler & heating costs.

Cost table

Indicative price ranges (UK, GBP)

Item	Typical range (GBP)
Fixed flat roof rooflight (600x900mm) — Double-glazed, aluminium frame	£600–£1,200
Opening flat roof skylight (1000x1500mm) — Electric opener, rain sensor	£1,200–£3,000
Roof lantern (1m x 2m) — Extension feature, structural	£2,500–£8,000
Roof lantern (2m x 3m) — Large extension or garden room	£5,000–£12,000

Labour costs

Labour typically accounts for 45% of the total project cost in the UK.

Labour line items

Item	Typical range (GBP)
Roofer / installation	£400–£1,200
Structural lintel (if needed)	£400–£1,000
Electrician (electric opener)	£150–£350
Internal finishing	£200–£600

Materials costs

Materials and fittings make up the remainder of the budget, with specification tier driving most of the variation.

Materials & fittings

Item	Typical range (GBP)
Fixed rooflight (600x900mm)	£300–£700
Electric rooflight	£700–£1,800
Roof lantern (aluminium, 1x2m)	£1,500–£4,000
Roof lantern (2x3m)	£3,000–£8,000

Factors affecting cost in the UK

·Region — London and the South East run 15–30% above national averages.
·Specification tier — premium materials and finishes can double the base cost.
·Access and site conditions — flats, restricted parking and listed buildings add time.
·Scope changes mid-project — late design decisions are the biggest cost overrun driver.
·Trade availability — quotes rise 10–20% in peak spring and summer months.

Hidden & unexpected costs

·Structural alterations to flat roof joists or trusses.
·Re-roofing or re-felting around the new opening.
·Internal lining, plastering and decorating the reveal.
·Building control sign-off for new openings.
·Blinds, electric openers and rain sensors.

Ways to reduce cost

·Choose standard sizes from Velux, Fakro or Roto rather than bespoke roof lanterns.
·Install a fixed rather than opening unit where ventilation isn't needed.
·Combine install with a planned flat roof replacement to share roofer labour.
·Fit a single large skylight rather than multiple smaller ones — cheaper per m² of glass.
·Skip electric openers unless out of reach.

Do you need permission?

Rooflights are usually permitted development if they do not project more than 150mm above the roof slope and are not higher than the highest part of the roof. Side-facing rooflights may need obscure glazing. Listed buildings and conservation areas often need consent.

Cutting a new opening into the roof structure needs building regulations approval because rafters are altered and the glazing must meet thermal standards.

Pitched vs flat roof

Pitched-roof windows are fitted between rafters, often from inside without scaffolding. Flat-roof lanterns and rooflights need a kerb or upstand built and the roof covering made good around it, which adds roofing labour.

Extras worth pricing

Blinds, electric or solar-powered opening, and finishing the reveal (plastering the lining between ceiling and window) are frequently left out of headline prices.

Frequently asked questions

What is the difference between a rooflight and a skylight?: These terms are often used interchangeably. A rooflight usually refers to a flat-roof-mounted unit (flush or slightly raised); a skylight often refers to units fitted into a pitched roof. Velux windows are technically rooflights for pitched roofs.
Does a skylight require planning permission?: A rooflight that doesn't protrude more than 150mm above the roof plane and is not on a front elevation is usually permitted development. Roof lanterns on extensions may require planning if they exceed certain heights.
Do skylights cause heat loss?: A quality triple-glazed rooflight or roof lantern has a U-value of 0.6–1.0 W/m²K, comparable to a good wall. Single glazed or low-spec units can cause significant heat loss. Always choose at least A-rated double glazing.

Sources & how we estimate

Prices are typical UK ranges compiled by ModernExpert.AI from published trade rates and supplier price lists, and are estimates — always get at least three written quotes. Rules on permissions, safety and certification come from the official sources below. Last reviewed 19 October 2026.

Found an outdated figure? Tell us and we'll check it.