Velux Loft Conversion London 2026: Complete Guide to Costs, Planning and Design
- LCCL Construction
- Jun 3
- 3 min read
A Velux loft conversion — also known as a rooflight loft conversion — is the most cost-effective way to convert a loft in London. By installing Velux or similar roof windows into the existing roof slope without altering the roof structure, a Velux conversion creates a habitable loft space at a significantly lower cost than a dormer or mansard. It is the right choice for properties with sufficient existing headroom and for homeowners where budget is the primary consideration. LCCL Construction delivers Velux loft conversions across London and Hertfordshire as part of our complete design and build service.
What Is a Velux Loft Conversion?
A Velux loft conversion installs roof windows — typically Velux brand or equivalent — into the existing roof slope to bring natural light into the loft space. Unlike a dormer or mansard, the roof structure is not altered — no new walls are built and the roofline remains unchanged. The loft is insulated, floored, plastered and fitted with a staircase, electrics and heating. The result is a usable loft room that costs significantly less than other conversion types. The key requirement is sufficient existing headroom — typically a minimum of 2.2 metres from the floor to the ridge at the highest point.
Velux Loft Conversion London: Costs in 2026
A Velux loft conversion in London typically costs between £18,000 and £48,000 in 2026 for a full design and build service. A basic Velux conversion creating one room costs £18,000 to £30,000. A larger Velux conversion with en-suite bathroom costs £28,000 to £48,000. See our full loft conversion cost guide for a comparison of all conversion types.
Does a Velux Loft Conversion Need Planning Permission in London?
Most Velux loft conversions in London fall within permitted development rights and do not require planning permission, provided the roof windows do not project more than 150mm above the plane of the roof slope and are not installed on the front elevation facing a highway. Properties in conservation areas require planning permission for Velux conversions on the front elevation but may be permitted on the rear. See our full guide to loft conversion planning permission in London.
Velux vs Dormer: Which Is Better for Your London Property?
A Velux conversion is the right choice when: your property has 2.2m+ of existing headroom at the ridge, budget is the primary consideration, you want to avoid planning permission, and you only need one modest room rather than a full bedroom suite. A dormer conversion is better when: you want maximum usable floor space with vertical walls, you want a full bedroom with en-suite, or you want to maximise the value added to the property. For most London terraced houses with standard roof heights, a dormer creates significantly more usable space than a Velux at a proportionally small additional cost.
How Much Value Does a Velux Loft Conversion Add in London?
A Velux loft conversion typically adds £40,000 to £70,000 to the value of a London terraced house — a return of 120 to 200 per cent on the construction cost. The return is lower than a dormer because less usable space is created. See our full guide on how much value a loft conversion adds in London.
Frequently Asked Questions About Velux Loft Conversions in London
How much does a Velux loft conversion cost in London?
Between £18,000 and £48,000 for a full design and build service in 2026. A basic Velux room costs £18,000 to £30,000. A Velux with en-suite costs £28,000 to £48,000.
Does my property have enough headroom for a Velux loft conversion?
You need a minimum of 2.2 metres from the floor to the ridge. LCCL Construction checks headroom and suitability as part of the free initial consultation.
To get a free consultation call LCCL Construction on 020 8037 7332 or get an instant quote online.
