Loft Conversion Cost Calculator
Plan a UK loft conversion by area, conversion type, and selected ensuite.
Market-specific data
Low, typical & high range
Assumptions shown below
Project measure
Project details
Refine the scope
Project options
Your planning estimate
UK estimate · 30 m²
Typical project allowance
£27,500
Low£22,500
High£30,000
This range updates from the project details you enter. It is a planning estimate, not a contractor quote.
Typical cost breakdown
- Base project allowance (30 m²)
- £27,500
Review the methodology below for included work, exclusions, assumptions, and source information.
Understand the range
Methodology, assumptions & sources
How this estimate is calculated
Type-specific rates are derived systematically from supplied 30m² project ranges. Ensuite and exceptional structural conditions are separate allowances.
This is a planning estimate, not a contractor quote. Actual quotes vary by location, specification, site conditions, labour, and project requirements.
Included assumptions & exclusions
- Roof structure, staircase, steelwork, access and specification can materially affect quotes.
- Building Regulations fees are not included.
Data sources & review information
Source reference
Checkatrade Loft Conversion Cost 2026
Source references provide benchmark context. HomeCostNest applies its own calculator structure, ranges, assumptions, and allowances; listing a source does not imply endorsement of HomeCostNest or verification of every calculated price.
No source URL is stored in this calculator's current data record; no link has been inferred or fabricated.
- Review date:
- September 19, 2026
- Dataset:
- 1.0
- Data record status:
- Reviewed internally
Helpful guides
Loft Conversion vs House Extension: Planning the Right Project
Compare existing-space conversion and new-floor-area projects without treating either as universally better.
Read planning guide
Loft Conversion Cost Guide: Dormer, Rooflight and Attic Conversion Costs
Compare rooflight, dormer, attic, and roof-modification project profiles using market-specific conversion methodology.
Read planning guide
Garage Conversion vs Loft Conversion Cost: Comparing Two Ways to Add Space
A market-specific cost-planning comparison of garage conversions and loft or attic conversions.
Read planning guide