London Loft Conversion Prices by Type
Not all loft conversions are equal. The type you choose has the single biggest impact on cost.
Velux (Rooflight) Conversion — £45,000 to £60,000 The most affordable option. No external changes to the roofline — just reinforced floors, insulation, fixed staircase, and rooflight windows. Only works if you already have adequate headroom (2.3m from floor to ridge, minimum).
Dormer Loft Conversion — £55,000 to £85,000 The most popular type in London. A box-shaped extension projects from the existing roof, adding headroom and usable floor space. Suits Victorian and Edwardian terraces well. Can accommodate a bedroom and en suite.
L-Shaped Dormer — £70,000 to £100,000 Two connecting dormers — one on the main roof, one on the back addition roof. Significantly more space. Common in London’s larger terraces. Typically requires planning permission.
Hip-to-Gable Conversion — £65,000 to £90,000 For semi-detached and detached homes with a hipped roof. The sloping side is replaced with a vertical gable wall, creating a much larger loft space. Often combined with a rear dormer.
Mansard Conversion — £80,000 to £120,000+ The most expensive and most disruptive. Near-vertical rear wall, flat roof, maximum headroom throughout. Almost always requires planning permission. Common in conservation areas and on larger London properties.
Why London Costs More Than the UK Average
London loft conversion costs run 15–25% above the national average. Four reasons:
Labour rates. Skilled tradespeople in London command higher day rates than anywhere else in the UK. This is unavoidable and reflects real market conditions.
Access and logistics. Narrow streets, CPZ parking restrictions, and terraced rows make material delivery harder. Scaffolding in central London often costs more due to pavement licensing and restricted space.
Period property complexity. Much of London’s housing stock is Victorian or Edwardian. Older roof structures often need additional strengthening once a builder is inside — costs that don’t appear on an initial quote.
Demand. London has more loft conversion activity than anywhere else in the country. Trade availability in peak season (March–October) is tight. Builders in high demand don’t discount.
What’s Included — and What Isn’t
A solid quote from a reputable London builder should include: structural work, dormer construction, roofing, windows, insulation, staircase, electrics, and plasterwork.
It typically excludes: architect or structural engineer fees (£1,500–£4,000), planning application fees if required (around £258 for most residential projects), building regulations inspection fees, and all finishing — flooring, decoration, bathroom fixtures, and storage.
Budget 10–15% on top of the build cost for these extras. A £65,000 dormer conversion realistically costs £72,000–£75,000 once finished.