Expert loft conversion builders across London. Post a job free — local builders contact you within hours.
Rooflights installed into the existing roof slope. The simplest and most affordable conversion — ideal where headroom is adequate.
Get quotes →A box-shaped structure built out from the roof slope. Adds standing headroom and is the most popular type in London terraces.
Get quotes →Extends a hipped roof to create a vertical gable end. Common on 1930s London semis, often combined with a rear dormer.
Get quotes →Near-vertical roof transformation maximising floor space. Popular in conservation areas across inner London. Usually needs planning.
Get quotes →Two dormers meeting at an L-shape — ideal for Victorian terraces with rear outriggers. Adds significant usable space.
Get quotes →Adds a bathroom or shower room to the new loft bedroom. Increases the value and practicality of the conversion significantly.
Get quotes →| Job | Low estimate | High estimate |
|---|---|---|
| Velux loft conversion (basic) | £20,000 | £35,000 |
| Dormer loft conversion | £35,000 | £65,000 |
| Hip-to-gable loft conversion | £40,000 | £70,000 |
| Mansard loft conversion | £55,000 | £90,000 |
| L-shaped dormer | £45,000 | £80,000 |
| En-suite addition | £6,000 | £15,000 |
| Party wall agreement (per neighbour) | £700 | £2,000 |
| Planning application fee (householder) | £206 | £206 |
| Structural engineer fees | £1,000 | £2,500 |
Prices are estimates for London 2026. Costs vary by conversion type, specification, and borough. Always get multiple quotes.
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Loft conversions are consistently the most popular home improvement project in London, and it is easy to see why. They add a new bedroom (and often a bathroom) to a property without reducing garden space, can usually be carried out under Permitted Development rights without a planning application, and deliver strong value uplift relative to cost. For the millions of Londoners living in Victorian and Edwardian terraces, the roof space is often the most underused area of the property — a well-designed dormer loft conversion transforms it into the most desirable room in the house. On 1930s London semi-detached houses, a hip-to-gable conversion can add significantly more floor space than a simple dormer, using the sloped hipped roof end to create a proper vertical gable and widening the loft considerably.
Party wall requirements apply to loft conversions on terraced properties — any work to the party wall or within 3m of a neighbour's structure requires a party wall notice served at least 2 months before work starts. Building regulations approval is required for all loft conversions regardless of whether planning permission is needed, covering structural calculations, fire safety (including escape routes and fire doors), insulation, and staircase requirements. Most London loft conversion builders handle both the structural engineer coordination and Building Control submissions as part of their standard service.
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