Price Guide · Updated 2026
Loft Conversion Cost London 2026
A complete breakdown of what loft conversions actually cost in London — by type, by area, and by what is and is not included. No vague ranges. Real prices from a London builder who does this work every week.
Loft Conversion Prices at a Glance
| Conversion Type | Typical London Price | Best For | Planning |
|---|---|---|---|
| Velux / Rooflight | £22,000 – £35,000 | Properties with 2.2m+ existing headroom | Usually PD |
| Rear Dormer | £38,000 – £55,000 | Victorian & Edwardian terraces | Usually PD |
| Hip-to-Gable | £45,000 – £65,000 | 1930s semis & detached homes | Usually PD |
| Hip-to-Gable + Dormer | £50,000 – £72,000 | Maximum space on semis | Usually PD |
| Mansard | £55,000 – £85,000 | Victorian terraces, maximum volume | Planning needed |
| L-Shaped Dormer | £48,000 – £70,000 | Victorian terraces with rear return | Usually PD |
PD = Permitted Development (no planning application required). Prices include structural engineering, building control, scaffolding, and full build. Excludes bathroom fixtures and decoration.
Rear Dormer Loft Conversion Cost London
A rear dormer is the most common loft conversion in London — particularly on Victorian and Edwardian terraces. It adds a box-shaped structure to the rear roof slope, creating full standing headroom and room for a proper bedroom with en-suite. Most rear dormers qualify under permitted development.
Typical cost: £38,000–£55,000. The lower end applies to straightforward terraced properties with good access. The higher end reflects larger dormers, complex roof structures, or conservation area materials requirements. Our quotation covers everything: structural steelwork, roofing, dormer window, insulation, staircase, first-fix services, plastering, and building control sign-off.
The bathroom within the loft is quoted separately once you have chosen your specification — typically £5,000–£12,000 for a full en-suite with shower, toilet, and basin.
Hip-to-Gable Loft Conversion Cost London
A hip-to-gable conversion extends the sloping side (the hip) of the roof to a vertical gable wall, dramatically increasing the usable floor area. It is the most popular option for 1930s semis and detached homes across North West, West, and East London. Most qualify under permitted development.
Hip-to-gable only: £45,000–£65,000. Most homeowners combine this with a rear dormer to maximise the space — a combined hip-to-gable and rear dormer typically costs £50,000–£72,000 and creates a genuinely large loft floor that fits a master bedroom, dressing area, and full bathroom.
On a 1930s semi in Edgware, Harrow, Ilford, or Ealing, this combination adds more value than almost any other single building project.
Mansard Loft Conversion Cost London
A mansard conversion replaces the entire rear roof slope with a near-vertical wall (typically 72°) and a flat or shallow-pitched roof, creating the maximum possible internal volume. It is the most expensive type but also delivers the most space and is common on Victorian terraces in inner London — Camden, Islington, Hackney, and Brixton.
Typical cost: £55,000–£85,000. Mansard conversions almost always require a full planning application — they change the roofline significantly. In conservation areas, the council will specify materials and may require the mansard to be set back from the ridge line so it is not visible from the street.
The build is more complex than a standard dormer — which is reflected in the price — but the resulting space is often equivalent to an additional full storey.
What Affects the Cost of a Loft Conversion in London?
Roof structure
Cut-timber roofs (common in pre-1960s houses) are straightforward to convert. Trussed rafter roofs (common post-1960s) require the trusses to be restructured with steelwork, which adds £3,000–£8,000 to the cost.
Head height
Less than 2.2m from floor joists to ridge means a dormer is essential to create usable space. Lower ridge heights sometimes mean the dormer needs to be taller and wider to achieve the minimum room height inside, which increases cost.
Access and scaffold
Tight terraced streets with no rear access mean all materials go through the house or over the roof. This adds time and cost — typically £1,500–£3,000 more than a property with easy rear access.
Conservation area
Conservation areas often require specific materials — matching brick or slate, timber windows rather than uPVC, lead-dressed dormers. These materials cost more and the planning process adds time (8–12 weeks for a decision).
En-suite specification
A basic en-suite (shower, toilet, basin, standard tiles) adds £5,000–£8,000. A premium en-suite with underfloor heating, large-format tiles, and high-end fixtures adds £10,000–£16,000.
Staircase position
The staircase is included in our quotation but the position matters. If the new stair needs to go somewhere awkward — through a bedroom or over an existing stair — structural work to accommodate it adds cost.
What Is Included in Our Loft Conversion Price?
Not included: bathroom fixtures and fittings, decoration, planning application fees (where required — typically £206 for householder applications).
Frequently Asked Questions
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