Realistic UK investment ranges for Velux, dormer and mansard loft conversions, updated for 2025–2026.
Loft conversions add bedrooms and living space without extending your footprint. This guide reflects typical fully managed projects including structure, staircase, windows, insulation, electrics, plastering and Building Control.
£28,000 – £42,000
Roof windows only. Most economical option where ridge height allows habitable space.
£42,000 – £58,000
Rear dormer adds head height and floor space. Popular for master bedrooms and en-suites.
£55,000 – £75,000+
Maximum floor area on hipped or terraced properties. Often requires planning permission.
Velux is most economical; dormer and mansard add significant structure and cost.
Minimum head height determines feasibility and usable floor area.
Access design affects existing rooms and build complexity.
Front dormers and mansards often require full planning permission.
Compare like for like: Ensure quotations include scaffolding, structural work, staircase, Building Control and full decoration.
Most lofts with 2.2m+ ridge height are suitable. We assess structure and access at a free survey.
Typically 6–10 weeks depending on type, access and specification.
Many rear dormers fall within Permitted Development. We advise at survey before you commit.
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