The Short Answer
On our estimates, fitting a flat rooflight or dome into an existing flat roof costs £900 to £1,800, including cutting the opening, building an upstand and making good. A 2m x 1m roof lantern is £2,200 to £4,500. Electric opening adds £600 to £720. The work takes from half a day to about three days.
A new opening usually needs building regulations approval, because the roof joists are cut and the roof around it has to be supported and made watertight. I'd add rooflights when the flat roof is being re-covered anyway.
Skylight and lantern prices
| Job | Typical cost |
|---|---|
| Flat rooflight or dome, about 1m², new opening | £900 to £1,800 |
| Roof lantern 2m x 1m, new kerb | £2,200 to £4,500 |
| Electric opening | Add £600 to £720 |
Domes, flat rooflights and lanterns
- Domes: a domed rooflight; the cheapest type.
- Flat rooflights: a flat glazed panel on an upstand.
- Pyramids and lanterns: pitched glazing in a frame standing up from the roof; the dearest, and the tallest, which matters for planning (below).
Building regulations and planning
- Approval: the Planning Portal says a new rooflight will generally need building regulations approval. The joists are cut and the cut ends carried on doubled timbers (trimmers), the joists either side may need strengthening, the roof has to carry the weight, the edges need weatherproofing, and a rooflight near a boundary has fire performance to consider.
- Energy: new rooflights must meet a U-value of 2.2 W/m²K (Approved Document L). Adding a lot of glazing brings in the limit of about 25% of floor area for windows, doors and rooflights before compensating measures are needed.
- Planning: rooflights are usually permitted development if they don't project more than 0.15m above the roof plane and aren't higher than the highest part of the roof. Lanterns stand taller, so check; conservation areas and listed buildings need checking too.
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Flat roof skylights and lanterns are priced by size and whether the roof needs a new opening.
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Frequently asked questions
How much does it cost to install a skylight?
On our estimates, £900 to £1,800 for a flat rooflight or dome in a new opening in a flat roof.
How much does a roof lantern cost to fit?
About £2,200 to £4,500 for a 2m x 1m lantern on a new kerb, fitted, on our estimates.
Do roofers put in skylights?
Yes, and so do window specialists and loft conversion firms. On a flat roof, a roofer can fit the rooflight and make the roof around it watertight in one job.
Do I need planning permission to put in a skylight?
Usually not if it doesn't project more than 0.15m and isn't above the highest part of the roof, but lanterns can stand taller than that, so check with the council. A new opening generally needs building regulations approval.
How we priced thisView sources (6, 4 official)
Rules come from the legislation and official guidance, read at source. Prices are our estimates: we check them against trade price data, retailer shelf prices and specialists' price lists, then build them up from their parts so the totals add up. Below are the sources behind the page; the trade price guides we only compare against aren’t listed. Where sources disagreed, we've said so. More on our method.
- OfficialBuilding regulations: rooflights, Planning Portal. Checked 15 Oct 2026.
- OfficialApproved Document L: Conservation of fuel and power, Volume 1 Dwellings (2021 edition incorporating 2023 amendments), GOV.UK. Checked 16 Oct 2026.
- OfficialThe Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 1, legislation.gov.uk. Checked 16 Oct 2026.
- OfficialRoof: planning permission and building regulations for re-roofing, Planning Portal. Checked 15 Oct 2026.
- IndustryExternal bifold doors and roof lanterns (shelf prices), Vufold. Checked 15 Oct 2026.
- IndustrySkypod roof lantern 1m x 2m (shelf price), Eurocell. Checked 15 Oct 2026.
