How much does a Velux window cost to install in 2026?

A roof window is one of the most cost-effective ways to bring daylight into a loft, a top-floor landing or a dark extension. In 2026 a typical Velux window cost runs from about £1,000 to £1,500 supplied and fitted, with replacements around £1,300 and many repairs costing a few hundred pounds. Velux is a brand name, but people use it for roof windows generally, and the prices and rules here apply to any make. We also cover planning permission and Building Regulations in Cambridge, where conservation areas and listed buildings are common.

How much does a Velux window cost in 2026?

Checkatrade’s skylight installation guide (September 2026) is the most detailed published source. It gives about £1,500 for a complete installation in its main table and about £1,000 in its FAQ, so we budget with the range rather than pretend there is one figure.

Job	Typical price	What it usually covers
New roof window, supply and fit	£1,000–£1,500	Window, flashing kit, cutting the opening, re-tiling and basic lining
Small Velux (as tabulated)	about £350	A small roof window project, per Checkatrade’s table
Large Velux (as tabulated)	about £900	A large roof window project, per Checkatrade’s table
Replace an existing window	about £1,300	Like-for-like swap into the existing opening
Electric opener	about £300 extra	Motorised opening for windows that are hard to reach
Flat roof dome rooflight	£300–£400	Simple dome on a flat roof upstand

Checkatrade’s tabulated small and large window figures sit well below its complete installation price, so read them as indicative and expect a full fitted price nearer the main range once access, flashing and internal finishing are included.

New opening or replacement?

Replacing an existing window is the simpler job. The opening, rafter trimmers and internal lining are already there, so the work is mostly removing the old frame, fitting the new one with a matching flashing kit and making good. Checkatrade’s Velux repair guide gives £1,000–£2,500 for a remove-and-replace job, and its roof repair guide says rooflight replacement starts from about £1,000.

A new opening involves more: stripping tiles or slates, cutting battens and membrane, trimming rafters to form the opening, fitting the frame, insulation collar and flashing, re-tiling around it and then plastering and decorating inside.

Electric and remote-control windows

An electric opener adds about £300, according to Checkatrade. It makes sense for windows out of reach, such as over a stairwell or high in a vaulted ceiling, and it is easier to add while the window is being fitted than afterwards.

What affects the cost of fitting a roof window?

• Size and type: Checkatrade’s table puts a large window at more than double a small one, and specialist designs such as conservation-style windows add to the price.
• Roof covering: slate and plain clay tiles take more careful cutting and flashing than interlocking concrete tiles. Checkatrade prices cutting tiles in against a Velux at about £10–£20 per metre.
• Access: a ground-floor extension needs little more than ladders; a second-floor roof may need a scaffold tower (about £250 a week) or full scaffolding.
• Structural work: a new opening that cuts through rafters needs proper trimming and building control.
• Inside finishing: plastering, lining, decorating and blinds are often priced separately.
• Location: a listed building may need a specific conservation-style window and consent first.

On Cambridge’s slate-roofed Victorian terraces, getting the flashing and slate cutting right is the difference between a window that stays dry for decades and one that leaks in the first winter. Our roof tiling and slating team handles the roof side of every installation.

How much does a Velux repair cost?

Checkatrade’s Velux repair guide (July 2026) puts most repairs at £165–£1,050:

Repair	Typical price
Replacement seals	£65–£150
Flashing or frame repair	£180–£500
Opening mechanism or hinges	£100–£500
Remove and replace the window	£1,000–£2,500

Why is my Velux window leaking?

There are three usual suspects. Water around the outside of the frame points to the flashing, or to tiles that have slipped against it. Drips at the edge of the glass often mean failed seals. And water running down the inside of the glass on a cold morning may be condensation rather than a leak, which better ventilation can solve. If you are not sure, our roof leak repairs service traces the source before anything is replaced.

Do Velux windows need planning permission?

For most houses, no. Roof windows fall under Class C of the General Permitted Development Order, which allows alterations to a roof provided they:

• do not protrude more than 0.15 m (150 mm) beyond the plane of the original roof slope;
• are no higher than the highest part of the original roof; and
• do not involve a chimney, flue or soil and vent pipe.

A window on a side-facing roof slope must also be obscure-glazed and non-opening unless the opening part is more than 1.7 m above the floor. The government’s householder technical guidance explains these limits with diagrams.

Roof windows in Cambridge conservation areas

Cambridge has 18 conservation areas, from Mill Road and De Freville to Newnham Croft and Chesterton. Greater Cambridge Shared Planning confirms that roof-lights there are still permitted development if they “do not extend more than 150 mm above the slope of the original roof” and “are not higher than the ridgeline”.

That does not mean anything goes. The council’s Mill Road appraisal lists “some over-dominant roof lights” as an issue, and the De Freville appraisal notes rooflights inserted into roof slopes. A modest size, a flush-fitting window and a rear slope rather than the street-facing one are the sensible choices.

Listed buildings, flats and Article 4

• Listed buildings: listed building consent is needed for a new rooflight, although householder planning permission is not. Unauthorised work to a listed building is a criminal offence.
• Flats and maisonettes: permitted development does not apply, so a new rooflight needs full planning permission.
• Article 4 and conditions: in Cambridge, only the Accordia estate off Brooklands Avenue has an Article 4 direction restricting alterations to homes, but older planning permissions can carry conditions. If in doubt, a lawful development certificate settles it.

Our guide to planning permission for roofing in Cambridge covers these rules in more depth.

Do you need Building Regulations approval for a roof window?

Usually, yes, but the route depends on the job:

• Replacing an existing roof window: the government lists roof windows and rooflights among work that installers registered with competent person schemes (such as FENSA, Certsure, CERTASS, NAPIT, ASSURE and Blue Flame) can self-certify. Otherwise the work is notified to building control.
• Cutting a new opening: trimming rafters is a structural alteration, and the Planning Portal says structural work needs a building control application.
• Part of a loft conversion: the window becomes part of a wider Building Regulations application, so talk to building control or your designer early.

Whoever fits your window, ask which route they will use and make sure you receive the certificate or completion notice at the end, then keep it with your house documents.

How long does a Velux installation take?

A straight replacement into an existing opening is the quickest roof window job. A new opening takes longer because of the structural trimming, re-tiling and internal finishing, and plastering needs time to dry before decorating. Because the roof is open during the work, installers plan it around a dry forecast. We confirm the time on site in writing with your quote, so you know exactly when the roof will be open.

Velux, rooflight or roof lantern on a flat roof?

On a flat-roofed extension, a flat-roof window or a simple dome (about £300–£400 according to Checkatrade) brings in light at a modest cost, and a glass lantern makes more of a feature. The upstand around any flat roof light is a common leak point, so it should be built properly into the roof covering. If your flat roof is due for replacement, fitting the rooflight at the same time is the cheapest moment; see our flat roofing page.

Get a fixed price for your roof

Whether you want a new window in the loft, a replacement for a tired or leaking one, or a straightforward repair, we survey the roof and the inside, check planning and Building Regulations for your property, and give you a written quote with a fixed price. Repairs come with our 5-year warranty. Find out more on our Velux windows and skylights page, call 01223 902596 (Monday to Friday, 8am to 5pm) or request a free quote.