Velux Flat Roof Window Questions: What Homeowners Ask Most
Whether you are researching a new flat roof extension, replacing an ageing skylight or comparing your options before committing to a purchase, Velux flat roof windows come up early in most searches. Below are the questions homeowners ask most often, answered directly, with the information needed to make the right decision for your project.
The Most Common Questions About Velux Flat Roof Windows
1. Does Velux make a flat roof window?
Yes. Velux produces a flat roof range under product names including the CFP (flat glass, fixed) and CVP (curved glass). These are separate products from their well-known pitched roof window range and are specifically designed for flat or very low-pitched roofs. However, the Velux flat roof range comes in fixed standard sizes, is manufactured in Denmark and is sold through UK merchants and distributors rather than direct from the manufacturer.
2. Can a standard Velux window be installed on a flat roof?
No. A standard Velux pitched roof window is designed to sit within a sloped roof at the same angle as the surrounding tiles or slates. It relies on the roof pitch to drain rainwater effectively. Installing a pitched roof window on a flat roof would result in water pooling, leaks and structural problems. For flat roofs, a purpose-built flat rooflight is the correct product.
3. How much does a Velux flat roof window cost?
Velux flat roof windows are priced through merchants and distributors, so the cost varies depending on the supplier and the size required. UK-made flat rooflights from Rooflights and Skylights UK start from £165 ex VAT for a 500x500mm frameless unit and from £392 ex VAT for a framed unit, supplied direct with no merchant markup. Roof lanterns start from £673 ex VAT.
4. What sizes do Velux flat roof windows come in?
The Velux flat roof range comes in a limited number of fixed standard sizes. If the roof opening falls outside those dimensions, a standard Velux unit will not fit without adapting the opening. UK-made flat rooflights from Rooflights and Skylights UK are available in standard sizes from 500x500mm to 1000x3000mm and in custom dimensions for any non-standard opening, delivered within 7 to 10 working days.
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Explore Flat Roof Skylights→5. Are Velux flat roof windows any good?
Velux is a well-established brand and their flat roof products are a recognised option in the market. Their flat roof range has limitations that lead many homeowners and builders to look at alternatives: fixed standard sizes only, European manufacturing with merchant-dependent supply and fewer glazing options than dedicated UK flat roof specialists. For most flat roof applications in the UK, a purpose-built domestic alternative offers faster delivery, greater sizing flexibility and direct manufacturer supply.
6. How long does a Velux flat roof window last?
A correctly installed flat roof skylight should last 20 years or more with basic maintenance. Longevity depends on the quality of the unit, the quality of the installation and how well the surrounding waterproofing is maintained. Every flat rooflight from Rooflights and Skylights UK carries a 10-year guarantee as standard, reflecting our confidence in the materials and manufacturing process behind every unit.
7. Do Velux flat roof windows need planning permission?
Most flat roof skylight installations on domestic properties are covered under permitted development rights and do not require a planning application, provided the installation remains within the existing roofline and meets the relevant height restrictions. This applies to any flat roof skylight, Velux or otherwise. Owners of listed buildings or properties within a conservation area should seek written confirmation from their local planning authority before any works commence.
8. What is the thermal performance of Velux flat roof windows?
Velux flat roof products offer double glazed options with thermal performance figures in line with standard flat roof skylight specifications. UK-made flat rooflights from Rooflights and Skylights UK achieve a U-value up to 1.0 W/m²K with double glazing and up to 0.5 W/m²K with triple glazing, using thermally broken aluminium frames to minimise cold bridging. Triple glazing is available across the full standard size range.
9. Can I replace a Velux flat roof window myself?
Replacing a flat roof skylight requires a qualified roofer with experience of flat roof glazing. The surrounding waterproofing membrane needs careful handling during removal, the upstand must be assessed and prepared correctly and the new unit must be sealed and integrated with the roof membrane to prevent water ingress. Installation by a qualified roofer or builder is always recommended. Contact our team on 0331 6303 671 for advice on what your installer needs to prepare before the replacement is carried out.
10. What is the best alternative to a Velux for a flat roof?
For UK homeowners looking for a Velux alternative on a flat roof, frameless and framed flat rooflights from Rooflights and Skylights UK offer several meaningful advantages: manufactured in Britain with UKCA certification, available in standard sizes from 500x500mm to 1000x3000mm plus custom dimensions, dispatched within 3 to 4 working days directly to site with free UK mainland delivery and carrying a 10-year guarantee on every unit. We have been recognised with the Professional Builder Top Product Award in both 2024 and 2025, voted for by tradespeople and builders across the UK.
11. How quickly can I get a flat roof skylight delivered?
Velux flat roof products are ordered through merchants and lead times depend on local stock levels. UK-made flat rooflights from Rooflights and Skylights UK are dispatched within 3 to 4 working days for standard sizes, with free delivery to all UK mainland addresses. Custom sizes are delivered within 7 to 10 working days. A £250 surcharge applies to deliveries to Scottish Highlands, Northern Ireland and the Channel Islands.
12. What glazing options are available for flat roof skylights?
Flat rooflights from Rooflights and Skylights UK are available with double or triple glazing and a choice of three glass types: clear Low-E glass for maximum light transmission, solar control glass for south-facing installations where heat gain is a consideration and satin privacy glass for bathrooms or overlooked spaces. All glazing options are available across the full range of standard and custom sizes.
UK-made flat rooflights — framed and frameless, standard sizes from 500x500mm to 1000x3000mm, custom sizes available. Standard sizes dispatched in 3 to 4 working days with free UK mainland delivery and a 10-year guarantee. Browse the full range at rooflightsandskylightsuk.co.uk/collections/rooflights-skylights