Loft Conversion Cost Calculator
Build an itemised working budget for a loft conversion in England. Adjust the type, size, specification, local-market scenario, bespoke work, professional costs, VAT and contingency, then check the likely planning route and site constraints.
Loft Conversion Budget Planner
Build a transparent England budget from verified July 2026 benchmarks
Baseline consumer-guide benchmark
A sensitivity control, not a regional price index.
Conversion Type Comparison
PD = permitted development; it still needs a property- and design-specific check.
Loft Conversion FAQs
Do loft conversions need planning permission?
Many house loft conversions can be permitted development, but this is not automatic. Class B includes volume, height, location, materials and design conditions, while flats, maisonettes and some restricted properties have different rights. Hip-to-gable work can sometimes qualify; mansard work commonly needs planning permission.
Do I need building regulations approval for a loft conversion?
A habitable loft conversion normally requires Building Regulations approval even when planning permission is not needed. The design must address structure, fire safety, insulation, stairs and other requirements. Agree the building-control route before work starts.
What is the cheapest type of loft conversion?
A roof-light or Velux conversion is usually the lowest-cost type because it can retain the main roof shape. A July 2026 Homebuilding benchmark gives a typical range of £30,000–£45,000, but feasibility depends heavily on the existing head height and structure.
How long does a loft conversion take?
The programme depends on design, structural work, access, approvals and contractor availability. Ask tendering contractors for a project-specific programme and separate the design and approval period from construction time.
Does a loft conversion add value to my home?
It can add usable space and value, but there is no reliable universal percentage. The result depends on local comparable sales, layout, build quality and whether the work has the necessary approvals. Compare the working budget with local valuations before committing.
What head height do I need for a loft conversion?
Around 2.2m from the existing floor joists to the ridge is a common early feasibility benchmark, not a universal planning rule. The finished height will be lower after strengthening and insulation, so a designer or structural engineer should survey the roof.