How Much Does It Cost to Fit a VELUX Window?

A quote for a roof window is really four smaller quotes added together. Seeing them apart is the quickest way to judge whether a figure is fair, because each part moves for a different reason.

On a straight swap, the roof work is small and the unit is most of the bill. With a new opening, the carpentry and the finishing can match the unit in cost, which is why the same window can be priced very differently on two houses on the same street.

Replacing an old unit in an existing opening means lifting the old frame, fitting the new one into the same gap and dressing the flashing back into your slates or tiles. The rafters stay as they are, so the job is quicker and the mess indoors is limited.

A new opening is a different kind of job. The roof covering is cut back, a rafter is trimmed and a header is fitted to carry the load, and the finish indoors has to be built up around the splayed reveal. It is building work, so it has to meet current regulations, and Building Control is told on your behalf if the job requires it. Expect the labour part of the quote to rise accordingly.

Fitting a whole new unit, rather than just its glass, is also notifiable work. If only the sealed glass unit is being changed in a sound frame, that generally is not, and it is usually the cheaper route when the frame is still in good order.

Bigger glass costs more to make, to deliver and to lift up a scaffold tower. VELUX labels each size with a letter for width and digits for height, so MK04 is a known, standard size. Our page on VELUX size codes walks through reading one off the frame. Standard sizes are the economical choice because the flashing kits are stocked, whereas a one-off size means a longer lead time.

Opening matters too. A top-hung sash that tilts outward from a pivot costs more than a fixed unit, and an electric or solar model from the VELUX INTEGRA range costs more again, because the motor, the rain sensor and the controls come with it. Whether that is money well spent depends on where the window sits. Over a stair void or a high landing, a motor and a rain sensor that closes the sash for you is a real convenience. Over a small box room you can reach, a hand-operated sash does the same job for less. Our guide to VELUX INTEGRA covers the electric range in more detail.

If the window comes from another leading maker, the answer on roof window fitting cost covers the same stack without the VELUX size codes.

Quotes that look cheap often leave out the items that appear later. Ask for each of these to be shown as its own line.

• Access. Scaffold or a tower, which matters on tall Georgian frontages in Clifton or Bath.
• Roof covering. Pennant stone slates, natural slate and clay tiles need careful handling and a matched flashing.
• Internal finish. Plastering the new reveal, and painting, are separate from the fit itself unless the quote says otherwise.
• Blinds. Roller or blackout blinds are an add-on. See VELUX blinds and accessories for what fits which window.
• Disposal. Taking the old unit and debris away.

Our quotes are written and itemised after a free survey, with no obligation, and opening options are shown on every one so you can compare a fixed unit with an opening one side by side. Roof windows in a conservation area, or on a listed building, may need permission first, and that can add time before the work can start.

Online calculators and printed price lists give a sense of scale, but they cannot see your rafters. Two things only show up on the roof itself: the spacing of the timbers, which decides whether a standard size drops in or needs a header, and the condition of the battens and felt around the opening.

That is why the survey comes before the number. We look at the roof from inside and out, measure the existing opening if there is one, and write down what is needed. The 10-year workmanship guarantee applies to the work itself, so the quote lists the fitting details you will be covered for. For the wider picture across every kind of rooflight, our costs page sets out the factors in one place, and the VELUX window installation service page shows what a complete job includes.