Compare rooflight, dormer, hip-to-gable and other loft-conversion budgets before requesting specialist quotes.
Applies to: UK homeowners. Building Regulations apply and planning requirements depend on the design and property.
Last checked: 3 October 2026
Key points
• Current guidance puts many loft conversions between about £27,500 and £75,000+.
• Dormer projects are currently published around £50,000 on average in one major guide.
• Structural changes, stairs, insulation and fire-safety work are major cost drivers.
• Building Regulations approval is required for loft conversions.
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Typical 2026 project figures
Current UK market guidance places rooflight/Velux conversions around £27,500, dormers around £50,000, hip-to-gable projects around £60,000 and mansard conversions around £65,000 as typical examples.
Why loft costs vary
• Existing roof structure.
• Required headroom and floor strengthening.
• Dormer or roof-shape alterations.
• New stairs.
• Fire-safety upgrades.
• Bathrooms or plumbing.
• Insulation, windows and finishes.
Approvals
Loft conversions must meet Building Regulations. Planning permission may also be needed depending on the type of alteration, permitted-development rights and property constraints.
Official sources
Use these official sources for the current detail that applies to your job, contract or location.
Further sources
Additional published guidance and research used in this article.
Pricing methodology
BuildPair reviews current UK market pricing references when preparing cost guides. Published figures are budgeting ranges, not BuildPair quotes or guaranteed local prices. Compare current local quotes before appointing a tradesperson.
BuildPair provides general information and signposting, not legal, structural, electrical, gas or building-control approval. Requirements can change and the right answer depends on the work, contract, location and facts.
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