Two parts to the price
"Velux" has become shorthand for roof windows in general. Whatever the brand, the cost of a fitted roof window splits into the window unit itself and the work to install it. The unit price is fairly easy to look up; the installation side varies much more from house to house, because it depends on the roof.
The window
- Size: larger windows cost more and may need wider openings between rafters.
- Opening type: centre-pivot, top-hung, fixed or conservation styles.
- Glazing: standard, enhanced thermal or noise-reducing panes.
- Operation: manual, electric or solar-powered.
- Extras: blinds, insect screens and remote controls.
Replacement or new opening
This is the biggest factor in Velux window installation cost. Velux window replacement in an existing opening of the same size is the simpler job: the old sash and frame come out, the new one goes in with fresh flashing, and the inside lining may need little work. A new opening means stripping tiles or slates, cutting and trimming rafters to form the hole, fitting the frame, flashing and underfelt collar, and then retiling around it. Inside, the reveal needs boarding, plastering and decorating.
Flashing and the roof covering
Roof windows need a flashing kit matched to the covering. Profiled concrete tiles, flat tiles and slate each take a different kit. Fitting a window into slate involves careful cutting and re-hanging of slates; on an older roof, matching replacements for any broken during the work can also come into it. Getting the flashing right matters, because a badly flashed roof window is a common source of leaks.
Access
Many roof windows can be fitted from inside, with some work from the roof. Others, on higher or steeper roofs, need scaffold or a tower. The number of windows matters too: fitting several at once spreads the access cost.
Structure and building rules
Cutting rafters changes the roof structure, so trimmers are added to carry the load. Very wide windows or several side by side may need more substantial trimming. Depending on your property and location, planning or building regulations may apply, so it's worth checking before committing.
Inside finishing
Plastering, lining and decorating around the window are sometimes left out of a quote. Ask whether they're included, and whether the price covers taking away the old window and waste.
Comparing quotes
Check that each quote names the window model and size, the flashing kit, whether rafters are being trimmed, who handles inside finishing, access costs and waste removal. Quotes that look cheaper often leave out one of these.
Roof windows and roof work together
If you're already planning a re-roof, it's often the easiest time to add or move roof windows, since the tiles are coming off anyway. Our pitched roofs and re-roofing page covers that work. If an existing roof window is leaking around its flashing, see our roof repair page.
Need it sorted? Talk to us about your roof
We don't offer a dedicated roof window installation service. For the roof work around windows, and leaks around existing ones, see our pitched roofs and roof repair pages, call 07399 680142 or use the quote form below.