How much does a loft conversion cost in London?Â
Most homeowners looking into a loft conversion have the same first question: what is this actually going to cost? It is a fair one, because loft conversion prices in London vary significantly depending on your roof, your property type, and the finish level you choose. This guide gives you realistic 2026 figures to work with before you start getting quotes. For most homes in East and North London, the cost of a loft conversion sits between £30,000 and £95,000. A standard dormer, which is by far the most popular choice, typically falls in the £45,000 to £65,000 range for a bedroom and en-suite.
Loft conversion prices by type in London
Velux loft conversion: £30.000–£40.000
The most affordable option. Skylights are fitted into the existing roof slope without altering the roofline, which keeps costs and build time low. Works best where there is already sufficient headroom in the loft. If budget is a priority and your roof structure allows it, this is the natural starting point.
Dormer loft:
£45.000–£65.000
The most popular choice across London's Victorian and Edwardian terraces. A dormer extends vertically from the existing roof slope, creating a box-shaped addition with full-height walls and a significant increase in usable floor space. Most homeowners use a dormer loft conversion to add a master bedroom with en-suite bathroom.
L-shaped dormer:
£65.000–£95.000
Common in Victorian terraces with an existing rear outrigger. Two dormers join in an L-shape over the main house and rear extension, creating a larger layout with space for multiple rooms. A popular choice for families who want a bedroom, bathroom, and a proper landing from a single conversion.
Hip-to-gable:
£50.000–£75.000
For semi-detached and end-of-terrace homes with a hipped roof, where the roof slopes on all four sides. Converting the slanted hip end to a vertical gable wall substantially increases the internal volume. Often combined with a rear dormer for maximum space gain.
Mansard loft:
£70.000–£95.000
The most substantial structural conversion available, common on terraced houses across Inner London. The existing roof slope is rebuilt to a near-vertical angle, effectively adding a full extra floor of headroom and space. The higher mansard loft conversion cost reflects the structural complexity and the planning permission this type typically requires.
Bespoke loft: £80.000+
For properties that need a tailored architectural solution, often combining two or more conversion types. Most common in heritage buildings, conservation areas, or homes with unusual layouts. Cost depends on the design and specification.
What affects the price
Beyond the conversion type, several factors move the final figure. Structural condition is a key one. Access and logistics matter on tighter London streets, where scaffolding and waste removal require more planning. Your choices for the staircase, windows, insulation, and finishes have a significant impact, particularly if you are adding an en-suite bathroom. Planning permission may be needed depending on the conversion type and whether your property sits in a conservation area. A party wall agreement is usually required if you share walls with neighbours, which adds time to the programme and some professional fees.
What does a loft conversion quote include?
A full loft conversion quote from LLAC covers structural work, roofing, insulation, windows, staircase, first and second fix, plastering, and decoration. What can vary between builders is the bathroom specification, the staircase design, and whether floor-to-floor making good is included. When comparing loft conversion costs across different quotes, check that the scope is genuinely like for like before comparing headline figures.
How long does a loft conversion take?
Build time varies by type. A Velux conversion is the quickest, while a mansard or L-shaped dormer takes longer due to the structural work involved. Most loft conversions take between 8 and 16 weeks on site. Your overall timeline will also depend on the planning or permitted development process, which should be factored in before the build begins.
Is a loft conversion worth the cost in London?
For most homeowners, yes. A well-executed loft conversion in East or North London typically adds more value to the property than it costs to build, particularly when a proper bedroom and bathroom are created. It also avoids the stamp duty, legal fees, and disruption of moving to a larger home, which in London can easily cost more than the conversion itself. The strongest returns tend to come in high-demand areas like Hackney, Walthamstow, Islington, and Haringey, where an extra bedroom makes a meaningful difference to what a property is worth and how quickly it sells.