UK Loft Conversion Costs: Complete Guide
How much does a loft conversion cost in the UK?
UK loft conversion costs typically range from £20,000 to £35,000 for a basic rooflight conversion, £35,000 to £55,000 for a dormer conversion and £45,000 to £70,000 or more for a large dormer or hip-to-gable conversion with an en-suite.
What this covers: Structural alterations, floor strengthening, staircase, insulation, windows, electrics, heating and internal finishing.
What changes the cost: Roof structure and available head height, conversion type, staircase position, whether an en-suite is included, Building Regulations requirements and the regional labour market.
These are indicative planning ranges for 2026 UK pricing, not contractor quotations or confirmed final costs. Property size, condition, location and specification all affect the final figure. Use the RenoCost renovation calculator for a range based on your own property, or obtain detailed written quotations before committing.
Use our calculator to estimate loft conversion costs based on your property and location
Start Your EstimateA loft conversion is one of the most cost-effective ways to add living space to your home without extending the footprint. Costs vary depending on the type of conversion, the size of your loft, and the complexity of the structural work required.
How This Estimate Is Built
Estimates are calculated from published UK cost benchmarks and RenoCost's own per-module cost assumptions, adjusted by postcode-based pricing region. Outputs are shown as low, mid and high ranges for initial planning, not contractor quotations. Every input is a deliberate user choice; no defaults are applied. Always obtain written quotations before committing to a project.
Average UK Loft Conversion Costs
Loft conversion costs in the UK typically range from £20,000 for a basic velux conversion to £70,000 or more for a large dormer or hip-to-gable conversion with en-suite bathroom.
Velux/Rooflight
£20,000-£35,000
typical range
Dormer
£35,000-£55,000
typical range
Hip-to-Gable
£45,000-£70,000+
typical range
Loft Conversion Types — Deep Dive
The four main loft conversion types differ in cost, complexity, planning treatment and the amount of usable floor area they create. The benchmarks below are aligned with 2026 UK industry pricing data and Building Regulations requirements.
Velux / Rooflight
6–8 weeks£20,000–£35,000
Roof windows are added to the existing roof slope without altering the structure. Suitable for lofts with adequate ridge height (~2.2m+) and good rafter condition.
Planning: Usually permitted development. Building Regulations approval still required (Parts A & B).
Dormer
8–10 weeks£35,000–£55,000 (~£1,500/m²)
A box-shaped extension projecting from the roof slope, increasing floor area and headroom. The most common type in the UK. See our detailed dormer loft conversion guide.
Planning: Rear dormers usually permitted development. Front dormers and conservation areas typically need planning.
Hip-to-Gable
10–12 weeks£45,000–£70,000+
Replaces the sloped hip end of the roof with a vertical gable wall, dramatically increasing internal volume. Only viable on semi-detached or detached homes with a hipped roof.
Planning: Often permitted development; planning required in conservation areas or under Article 4 directions. Party-wall agreements may apply.
Mansard
12–16 weeks£55,000–£100,000+
A full restructure of the roof to create near-vertical walls and a shallow flat top — maximising floor area and ceiling height. Common on London terraced homes.
Planning: Almost always requires full planning permission. Allow 8–12 weeks for approval.
Planning Permission and Building Regulations
Many loft conversions do not require planning permission, although Building Regulations still apply. Larger structural changes, front-facing dormers, conservation areas and properties with Article 4 directions can require planning approval. This is England-specific guidance; planning and building-control rules differ in Scotland, Wales and Northern Ireland, so check the Planning Portal or GOV.UK and your local authority before starting work. All conversions must comply with UK Building Regulations including:
- • Structural integrity (Part A)
- • Fire safety (Part B)
- • Insulation and energy efficiency
Regional Cost Variation
Loft conversion costs vary across the UK due to differences in labour rates, material costs and access constraints.
- • London and South East: +20–60% above national baseline
- • Midlands: baseline national rates
- • North: -10–15% below baseline
What Affects Loft Conversion Costs?
- • Type of conversion
- • Size of loft and headroom
- • Structural requirements
- • Staircase design and location
- • En-suite bathroom installation
- • Regional labour rates
Loft Conversion Cost Guides
From the Insights
UK Renovation Cost Index 2026
How material and labour costs have shifted across the UK this year.
Average Costs by Region
Regional benchmarks comparing loft conversion and renovation costs across UK regions.
Hidden Costs Homeowners Miss
The line items that quietly inflate loft conversion and renovation budgets.
Live UK Renovation Data
Live, anonymised loft conversion activity from completed RenoCost calculator sessions — updated automatically.
Sources & Methodology
Pricing on this page is informed by a mix of public macro benchmarks and RenoCost's own datasets and assumptions, listed below. See the Method Glossary for definitions of the terms used.
- GOV.UK — Permitted Development RightsOfficial guidance on permitted development for loft conversions and dormers in England.
- Planning Portal — Loft ConversionsReference for planning permission and permitted development conditions affecting loft projects.
- UK Building Regulations — Approved DocumentsStatutory technical standards for structural integrity (Part A), fire safety (Part B) and energy efficiency.
- RICS Global Construction MonitorRICS quarterly survey of construction market sentiment and tender pricing, including UK regional data used to validate labour and material trends.
External benchmarks above are used only as macro reference points. None of the organisations listed has reviewed, endorsed, validated or partnered with RenoCost. Specific cost figures on RenoCost reflect RenoCost's own per-module assumptions and completed calculator estimates, and should not be attributed to any external body.
How We Calculate Costs
RenoCost estimates are calculated from published UK cost benchmarks and RenoCost's documented per-module cost assumptions. The model adjusts these assumptions using the property characteristics, selected renovation scope, finish level and broad postcode-based pricing region, then presents a low, mid and high planning range.
- Published UK benchmarks — macro reference points for construction costs and materials and labour trends, used to sense-check RenoCost's own assumptions.
- RenoCost's per-module assumptions — cost and duration assumptions for each renovation module, reviewed and updated periodically by the RenoCost team.
- Estimate ranges — low, mid and high bands set to reflect the realistic spread between competitive and premium specifications, rather than a single fixed price.
Data confidence note
Completed calculator estimates are used to produce anonymous renovation-planning insights. They are not contractor quotations, invoices or confirmed final project costs. RenoCost estimates are intended for initial planning and budgeting. Property condition, specification, access, contractor availability and site-specific requirements can change the final cost. Always obtain detailed written quotations before committing to a project.
Regional adjustments are applied based on postcode area to reflect broad differences in local labour and material rates. See our Method Glossary for definitions of the terms used here.