The Short Answer
On our estimates, swapping an old roof window for a new one in the same opening costs £700 to £1,300 fitted. Adding a new roof window to a pitched roof, which means cutting the roof, trimming rafters, flashing and lining the opening inside, is £1,000 to £2,000. Electric or solar opening adds £400 to £800.
One window usually takes about a day. Velux says most replacements can be done safely from inside without scaffold; on high or awkward roofs a tower (£250 to £450 a week) or scaffold adds to the bill.
Roof window prices
| Job | Typical cost, fitted |
|---|---|
| Like-for-like replacement | £700 to £1,300 |
| New roof window in a pitched roof | £1,000 to £2,000 |
| Balcony roof window | £2,800 to £3,800 |
| Electric or solar instead of manual | Add £400 to £800 |
| Scaffold tower if needed, a week | £250 to £450 |
Building regulations and planning
- Replacing a roof window is controlled work, like any replacement window: it must meet 1.4 W/m²K (or the energy rating equivalent), and an installer in a competent person scheme (FENSA, CERTASS, Assure, Blue Flame, Certsure or NAPIT) can self-certify it.
- A new roof window generally needs building regulations approval, the Planning Portal says: rafters are cut and the cut ends supported with doubled timbers (trimmers), the rafters either side may need strengthening, the roof has to carry the window's weight, and a window near a boundary has fire performance to consider.
- Escape windows: if the room needs an escape window, a roof window can only serve as one if it meets the escape opening rules (at least 0.33m² of clear opening).
- Planning: roof windows are usually permitted development if they don't stick out more than 0.15m from the roof slope and aren't higher than the ridge; side-facing ones must be obscure glazed and non-opening below 1.7m. Check first in a conservation area or on a listed building.
Choosing a roof window
- Centre pivot: the cheaper type.
- Top hung: dearer; opens outward from the top.
- Electric or solar: for windows out of reach.
- Size: Velux's own guidance is that a room's glazed area should be at least 20% of its floor area for good daylight (a maker's recommendation, not a rule).
- I'd order any blinds at the same time.
Who fits roof windows?
Roofers, window specialists and loft conversion firms all fit them, and Velux runs its own supply-and-fit replacement service. Fitting one yourself means working at height and, for a new opening, cutting the roof structure and getting building regulations approval, so I'd only do it if you're genuinely competent at both.
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Frequently asked questions
How much does it cost to fit a Velux window?
On our estimates, £1,000 to £2,000 for a new one in a pitched roof, or £700 to £1,300 to replace an existing one.
Do roofers install Velux windows?
Yes, and so do window specialists and loft conversion firms. Velux also offers its own replacement service.
Can I install VELUX myself?
It's possible, but it's work at height, and a new window cuts the roof structure and generally needs building regulations approval. A replacement fitted by a registered installer is certified for you.
Do I need planning permission to put a VELUX in my roof?
Usually not, if it projects no more than 0.15m from the roof and isn't higher than the ridge. Check if you're in a conservation area or the house is listed.
Do Velux windows need building regulations?
A replacement is controlled work that a registered installer can self-certify. A new opening generally needs building regulations approval because rafters are cut and trimmed.
How long does it take to fit a roof window?
Usually about a day for one, often from inside without scaffold.
How we priced thisView sources (7, 6 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.
- OfficialApproved Document B: Fire safety, Volume 1 Dwellings (2019 edition incorporating 2020 to 2026 amendments), paras 2.10, 2.16 and 2.18 to 2.20, GOV.UK. Checked 16 Oct 2026.
- OfficialThe Building Regulations 2010, Schedule 3: self-certification schemes (para 16, roof coverings), legislation.gov.uk. Checked 15 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.
- IndustryRoof window replacement costs, Velux. Checked 15 Oct 2026.
