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A dark, stuffy loft or upstairs room can feel like wasted space. One roof window can change that. It floods the room with daylight and fresh air, and it is one of the quickest ways to make a space feel bigger without changing your home’s footprint. But the quoted price is rarely just the cost of the window, and that is where many homeowners get caught out.
In 2026, installing a Velux roof window in the UK typically costs roughly £800 to £2,200 per window, fitted. A like-for-like replacement sits at the lower end, while cutting a brand-new opening into the roof costs more, and balcony styles cost considerably more. In this guide, we break down what you pay for, what drives the price up, and how to avoid mistakes that can cause leaks later.
The cost depends mainly on whether you are replacing an old window or adding a new one. These are typical fitted prices per window in 2026, including the window, flashing and labour, but excluding scaffolding and internal finishing.
| Type of job | Typical cost per window (2026) | What to expect |
|---|---|---|
| Like-for-like replacement | £800 to £1,700 | Usually about four hours, with no structural work |
| New window in an existing roof | £1,200 to £2,200 | Includes cutting the opening, trimming rafters and fitting flashing |
| Balcony or large window | £3,500 and above | The window alone starts at around £2,500 before VAT, and the job takes longer |
| Several windows in one visit | Lower cost per window | Labour, access and scaffolding are shared across the job |
| Project | Approximate Cost (£) |
|---|---|
| Removing the old window or cutting the new opening | £150 – £300 |
| Fitting the window and sealing it into the roof | £200 – £400 |
| Interior finishing (plasterboard, lining, decorating) | £100 – £250 |
| Scaffolding or access equipment (if required) | £150 – £400 |
| Waste removal (old window, tiles, debris) | £50 – £120 |
| Total labour (estimate) | £650 – £1,470 |
| Item | Approximate Cost (£) |
|---|---|
| Velux window unit (depends on size and glazing) | £250 – £700 |
| Flashing kit (matched to your tile or slate type) | £60 – £150 |
| Insulation collar/vapour barrier | £40 – £100 |
| Interior lining kit and small fittings | £30 – £90 |
| Total material (estimate, before VAT) | £380 – £1,040 |
Two homes with the same window can receive very different quotes. These are the main factors.
A like-for-like replacement is the simplest job. The installer removes the old window and flashing, fits the new unit into the same opening and seals it. It can often be finished in around four hours. VELUX’s own figures put labour at about £550 to £650, plus the cost of the window. Older windows with different dimensions may need an adapter or a modified opening, which adds cost.
A new window costs more because the installer has to open up the roof. The installer cuts through the roof covering and battens, trims and supports the rafters where needed, then fits the frame, flashing and waterproofing layers. If the window serves a loft conversion, the opening may also need to meet Building Regulations for structure, insulation and fire safety. A good installer inspects the roof first and explains what the opening requires before you commit.
In most cases, roof windows that don’t stick out more than 150mm from the roof slope are permitted development, so you usually don’t need planning permission. The rules are stricter for flats, listed buildings, and homes in conservation areas, National Parks and Areas of Outstanding Natural Beauty. Much of Dorset falls into these categories, so check with Dorset Council or BCP Council before ordering windows. In a conservation area, a low-profile conservation-style roof window is often the safer choice. Roof windows must also comply with Building Regulations, which a registered installer can usually certify. These rules apply in England and can change, so confirm them on the Planning Portal and with your local council.
A roof window is an opening in your roof that has to stay watertight for decades. The window itself rarely fails. Most problems come from poor flashing, poorly lapped membranes, and weak seals around the frame, and they show up as damp patches, stained ceilings, and mould, often months after the work is finished. Paying a little less for a poor fit can cost far more in repairs later.
That is why the installer matters as much as the product. As roofers, we fit every Velux window as part of the roof, not as an add-on. At Extreme Pro Roofing, we install Velux windows across Dorset, sealing each one properly into the roof so it stays dry, bright, and trouble-free. Whether you need a like-for-like replacement or a brand-new opening, our team inspects the roof first, explains the options in plain English and gives you a clear written quote before any work starts.
Before you commit, a short roof inspection shows exactly what the job needs and what it will cost. As a professional roofing company, we handle the roof opening, window fitting, and waterproofing in one job, so you deal with one team and one standard of work. Our professional roofing contractors can check your roof covering, advise on the right window size and type, and explain whether a replacement or a new opening makes sense for your home.
Contact us today for a free, no-obligation quote and clear advice on the right Velux window for your home.
Planning a new roof? Our roof installation and replacement team gives free, no-obligation quotes across Dorset. Speak to the roofing and guttering specialists in Dorset.
Call 07476557149A like-for-like replacement can take around four hours. A new opening usually takes longer because the roof has to be cut, supported and waterproofed, and a larger or balcony window can take more than a day.
Most pitched roofs can take one, including tile and slate roofs. Roof pitch, rafter layout, and headroom inside all matter, and flat roofs need a different type of window or rooflight. An installer should inspect the roof before quoting.
A roof window brings in daylight and ventilation and makes a loft or upstairs room more usable, which helps a home appeal to buyers. The value it adds depends on the room and the quality of the finish, so it is hard to put a single figure on it.
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Extreme Pro Roofing are roofers in Dorset providing professional roofing services including roof installation, roof repairs, roof maintenance, flat roofing, chimney repairs, leadwork, fascia, soffits and guttering, dry verge and ridge installation, conservatory roof replacement, loft conversions, Velux window installation and 24/7 emergency roofing across Dorset, Bournemouth, Southampton and Salisbury.
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