Loft Conversion Cost UK
A loft conversion is one of the most effective ways to add living space and value to your UK home without extending the footprint. Whether you need an extra bedroom, home office, or bathroom, converting your loft can transform unused roof space into valuable accommodation.
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Calculate My Loft Conversion CostUK Loft Conversion Costs by Type (2026)
Velux/Rooflight Conversion
£20,000 - £35,000
No external changes, quickest option
Dormer Conversion
£35,000 - £55,000
Most popular, adds headroom
Hip-to-Gable Conversion
£45,000 - £65,000
Extends roof at one or both ends
Mansard Conversion
£55,000 - £80,000+
Maximum space, major structural work
Types of Loft Conversion Explained
Velux/Rooflight conversions are the simplest and most affordable option. They involve adding roof windows without changing the roof structure, making them ideal for lofts with adequate head height.
Dormer conversions extend vertically from the sloping roof, creating additional floor space and headroom. They are the most common type in the UK and work well for most property types.
Hip-to-gable conversions extend the sloping side of a hipped roof outward to create a vertical gable wall, significantly increasing usable space. This is particularly popular for semi-detached and detached houses.
Mansard conversions involve significant structural changes to create a nearly flat roof with steeply sloping sides. They offer maximum space but require planning permission and are most common in London.
What Affects Loft Conversion Costs?
- Conversion type: Velux is cheapest, mansard most expensive
- Size: Larger lofts need more materials and labour
- Staircase: Standard straight stairs cost less than spiral or space-saving designs
- En-suite bathroom: Adds £4,000-£8,000 to the project cost
- Roof structure: Traditional rafters are easier to work with than modern trusses
- Insulation and glazing: Meeting building regulations adds cost but improves comfort
- Location: London and the South East have higher labour costs
What Is Typically Included?
A standard loft conversion includes structural work and steel beams, floor strengthening, staircase construction, roof windows or dormer construction, insulation to building regulations, electrics and lighting, plastering, and basic decoration. Bathroom fitting, carpentry, and high-end finishes are often extras. Additional costs such as structural steel and fire safety upgrades can significantly impact overall loft conversion budgets, particularly on terraced properties where access and party wall considerations apply.
Planning Permission and Building Regulations
While many loft conversions fall under permitted development rights, all conversions require building regulations approval. This covers structural safety, fire escape routes, insulation, and staircase design. Building regulations fees typically add £500-£1,000 to the project, and inspections are required at various stages. Loft conversions may require architectural drawings and technical design. These can be estimated separately using the architect fees calculator. Homeowners planning their budget should also factor in the hidden costs of loft conversions that arise from compliance with Approved Documents A, B and L.
Calculate Your Loft Conversion Cost
Get a personalised estimate for your loft conversion using our free calculator. Enter your property details, location, and conversion type to see realistic cost ranges based on current UK construction prices.
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.