How much does it cost to install a Velux window?
A roof window is priced per window, supplied and fitted into the roof. Get an indicative figure below.
What fitting a roof window involves
- 1Form the opening
The roof covering is opened up and, if the window is wider than a rafter bay, the rafters are trimmed and supported.
- 2Fit and flash
The window is set in with the correct flashing kit for the roof covering so it's fully weathertight.
- 3Internal finish
The reveal is lined and plastered inside — the finish that makes it look built-in rather than added.
Roof windows are the cheapest way to flood a loft or top floor with light — a common, high-impact move in a loft conversion. Get the flashing right for the roof covering; a leaking Velux is a classic false economy.
Roof window costs (indicative, supply & fit)
| Type | Per window | Notes |
|---|---|---|
| Standard manual | £900 – £1,500 | Incl. flashing & finish |
| Electric / solar-opening | £1,300 – £2,200 | Remote, rain sensor |
| Larger / altered rafters | £1,500 – £2,800 | Structural work |
| Window only (supply) | £250 – £700 | Before fitting |
Includes flashing kit, making good and internal lining. Cutting through/altering rafters adds structural cost.
Frequently asked questions
How much does it cost to install a Velux window?+
A standard roof window supplied and fitted with flashing and internal finish typically costs £900–£1,500; electric or larger windows needing rafter alterations cost £1,300–£2,800.
Do I need permission for a roof window?+
Roof windows that sit in line with the roof slope are usually permitted development, but conservation areas and windows to the front elevation can differ — check locally. Loft conversions have their own rules.
Related tools & guides
Want to know how these figures are calculated? See our cost methodology.
Cost figures shown are indicative estimates, not quotations. You are responsible for verifying all costs (obtain contractor quotes) and any figures submitted to a lender. ScopeWise is a documentation tool, not financial, tax, structural or planning advice. HMO compliance prompts are guidance only — confirm requirements with your local council, as standards and licensing vary by authority.