Velux and Roof Window Installation Costs and the Rules to Know

A standard mid-range roof window costs an average of £1,100 to supply and fit in the UK. Most standard installations take about one day to complete. This guide explains what you can expect to pay for different types of rooflight and sets out the planning and building regulations rules you need to follow.

What a roof window costs fitted

When you ask for a quote, the price will depend on the size and style of the window. A top-hung roof window is hinged at the top. A centre pivot roof window turns on a hinge in the middle of the frame. A balcony style roof window is larger and opens out to form a small balcony.

The table below shows the typical supply and fit costs for different window styles.

The figures in the table are typical published prices for 2026. For example, a small centre pivot manual white painted window is £655 supplied and fitted, against £3,050 for a small balcony style window. Prices are generally higher in London and the South East, and local quotes will always vary depending on your specific roof.

Supply only and replacement prices

If you prefer to buy the window yourself, the prices are significantly lower, but you will still have to pay a roofer to fit it. A top-hung white painted window is £430 for a small unit and £670 for a large one to supply only. A centre pivot manual white painted window costs £330 for a small size and £490 for a large one. A balcony window costs £2,400 to £2,800 to buy without fitting.

A replacement is around £100 less than a new installation for a straightforward swap. Replacing a small skylight costs about £500 for a non-branded unit or £550 for a branded one, and a large skylight about £700 or £800.

What labour and scaffolding add

The price of the window is only one part of the bill. The general rule for labour is an install price of £325 a day. London and the South East usually cost more for daily labour rates, so you should expect quotes to reflect local living costs.

Working at height needs safe access. Third-party scaffolding is listed at £500 per day, and this is on top of the window price. You should always read your quote carefully to see if the scaffolding cost for roof work is included or billed separately by your roofer.

How long fitting takes

The time it takes to fit a roof window depends on the size of the unit and the structure of your roof. A standard installation takes between 6 and 8 hours, which is why the labour is typically charged at a single day rate of £325. Fitting a complex balcony window takes 1.5 days or more, pushing the labour cost to £490 or higher.

If you decide to have two smaller windows instead of one large one, this will add roughly 3 to 4 hours to the job. For a replacement job, swapping a small skylight takes 4 to 6 hours. Swapping a large skylight takes 6 to 8 hours to complete. Ask the roofer to confirm in writing that the quoted labour covers the full time the job needs, since a balcony window takes 1.5 days or more against 6 to 8 hours for a standard one.

Does a roof window need planning permission?

In England, installing a roof window is generally classed as permitted development as an alteration to the roof. This means you do not normally need to apply for planning permission if you meet certain limits. The window must not project more than 150 millimetres from the plane of the existing roof slope.

The window must also not exceed the height of the existing roof. If you are fitting side-facing windows, they must be obscure-glazed. If these side-facing windows open, the opening part must be 1.7 metres above the floor of the room.

You can check the full permitted development limits on the Planning Portal. The guidance relates to England, and policy in Wales may differ. Readers in Scotland and Northern Ireland should check with their local council rather than guessing.

Building regulations for roof windows

According to the Planning Portal, approval under the Building Regulations will generally be needed for the installation of a new rooflight. The main reason is that cutting the opening usually means cutting the timber rafters or joists.

When these timbers are cut, the roof needs new supports called trimmers to carry the load safely. The rooflight must also prove it provides sufficient insulation against heat loss to meet thermal performance standards known as Part L and U-value rules. If you are replacing the whole covering at the same time, you may also need to look into the building regulations for a new roof.

The rules also look at fire performance if the window is close to a boundary line. Finally, the room must be ventilated, the roof void must be kept ventilated to prevent damp, and the edges and glazing must be completely weatherproofed.

Listed buildings, flats and conservation areas

The permitted development rules do not apply to every type of home. The house must not be a building containing one or more flats, or a flat within such a building. Permitted development does not cover flats or maisonettes at all.

If the limits are not met, or permitted development rights have been removed in your area, a householder or full planning application is required. The Planning Portal page does not set out the rules for listed buildings or conservation areas, so check with your local council before you plan any work.

How the window is fitted into your roof

To fit the window on a pitched roof, the roofer has to remove the outer covering. A pitched roof is a standard sloping roof, unlike a flat roof. The covering might be concrete and clay tiles, or it might be natural and fibre cement slate.

Underneath the tiles, your roof has timber battens and a waterproof underlay, which is often called felt or membrane. Cutting the opening usually means cutting rafters or joists and fitting new trimmers, which is structural work for a qualified roofer or builder. The edges and glazing must then be weatherproofed, often with lead flashing, the shaped metal strip used to seal joints. The rules above matter at this stage too, because the structural opening, the insulation value of the window and the weatherproofing of its edges are the points building control looks at. Ask your roofer to confirm in writing who is responsible for the application.

For flat roofs, the systems are different. Flat roof systems include built-up felt (usually torch-on), EPDM rubber, GRP fibreglass, single-ply and liquid coatings. A window on a flat roof is fitted into the timber deck, which is the structural wooden base. If you have a warm roof, the insulation sits above the deck, but if you have a cold roof, the insulation sits between the joists.

Choosing a roofer for the job

You should always get three written quotes for a roof window installation. A written quote is a fixed price, while an estimate is just a rough guess that can go up later. Be wary of cold callers who knock on your door claiming they have spotted a loose tile or moss from the street and offer to fit a window cheaply.

A good roofing firm will provide an itemised price and proof of their insurance. Under the Consumer Rights Act 2015, all work must be done with reasonable care and skill. If it is not, you can ask for it to be put right or for your money back. Paying by credit card gives you Section 75 protection on purchases over £100 and up to £30,000, and Citizens Advice is the place to go if you end up with a dispute.

Questions to ask before you book

Before you agree to any work, you need to know exactly what is included in the price. Ask your roofer the following questions so you do not face unexpected bills at the end of the job.

• Who handles the building control application and the paperwork?
• Is the lead flashing included in the quoted price?
• Is the scaffolding included or billed as a separate daily cost?
• Is making good internally included, such as plastering around the new window frame?
• What guarantee comes with the work and is it insurance-backed?
• Are waste removal and VAT included in the final figure?

Common questions

Can I install a roof window myself?

You should not attempt to fit a roof window yourself. Cutting rafters is structural work that must be done by a qualified roofer or builder. If you cut the wrong timbers without adding proper support, your roof could sag or collapse.

What happens if the roofer finds rotten wood?

Nobody can see rotten timber until the old covering is off. A good quote will always say how extras will be priced if the roofer finds damp or damaged wood underneath your tiles.

Do I have to pay if I cancel my contract?

Contracts agreed at home, by phone or online normally carry a 14-day cooling-off period. However, if you ask for work to start inside that period, you must pay for what has been done if you then decide to cancel.

Can I put a roof window in a solid conservatory roof?

If you are upgrading an old conservatory, you need to be careful with the rules. Replacing a glazed or polycarbonate conservatory roof with a solid one takes the conservatory out of its exemption. This means building regulations apply to the new roof.

Are there different rules if I replace my whole roof?

If a roof window is fitted as part of a larger project, other rules can apply. In England, repairing or re-covering a roof does not normally need a building control application if less than 25 per cent of the building envelope and less than 50 per cent of the roof is affected. Above that, approval is needed and the insulation may have to be upgraded.

Next steps before you hire

• Take photos of the space inside your loft and the roof outside from the ground.
• Check the Planning Portal to see if your plans fall under permitted development.
• Ask three local roofers for itemised, written quotes.
• Confirm in writing who is dealing with the building regulations approval.
• Agree a staged payment plan and only make the final payment when the job is completely finished.

Fitting a roof window involves cutting into the structure of your roof. Take the time to check the rules, insist on proper paperwork, and use our directory to find a roofer near you and compare written quotes.