Renovation Cost Calculator

This calculator provides a ballpark estimate based on 2025 London market rates. It is accurate to within approximately 15-20% for most projects. Actual costs depend on site-specific factors such as access, ground conditions, structural requirements and your exact specification choices. For a precise quote, we recommend booking a free site visit with our team.

The cost per square metre includes all construction labour, materials, project management and standard finishes for the chosen specification level. It does not include professional fees (architecture, structural engineering), planning application costs, party wall agreements or VAT — these are shown separately in the full breakdown.

Basement conversions involve significant structural work including underpinning, waterproofing (tanking), soil excavation and removal, temporary structural support and specialist drainage. The engineering complexity, the need for party wall agreements with neighbours, and the London-specific challenges of working below the water table all contribute to higher costs compared to above-ground renovations.

Yes. Prime Central London postcodes (SW1, SW3, SW7, W1, W8) typically command a 20-25% premium due to higher parking/access costs, stricter council requirements and more demanding client expectations. Inner premium areas like Hampstead (NW3) and Highgate (N6) sit around 10-15% above the London average. Our calculator applies these postcode-based multipliers automatically.

These estimates do not cover loose furniture, kitchen appliances (unless built-in), curtains and soft furnishings, garden landscaping, external decorations, or any specialist items like home cinema systems, wine cellars or swimming pools. Demolition of existing structures and asbestos removal, if needed, would also be additional costs assessed during a site survey.

The specification level primarily affects materials and fixtures. Standard uses quality but widely available materials — good ceramic tiles, laminate worktops, standard sanitaryware. Premium steps up to engineered hardwood flooring, natural stone worktops, designer taps and better insulation. Luxury means bespoke joinery, Carrara or book-matched marble, underfloor heating throughout, smart home automation and architect-specified fixtures from premium European brands.

Timelines vary by project type: a bathroom renovation typically takes 3-4 weeks, a kitchen 4-6 weeks, a loft conversion 8-12 weeks, an extension 10-16 weeks, a basement conversion 16-24 weeks, and a full refurbishment 12-20 weeks. These are on-site construction times; add 6-12 weeks for design and planning beforehand. Our project managers provide a detailed programme during the quotation stage.

It depends on your project and property. Many loft conversions and single-storey rear extensions fall under Permitted Development rights and do not need a formal planning application. However, properties in conservation areas, listed buildings, flats and some larger projects will require planning permission. Basement conversions in several London boroughs now require planning approval. Our team can advise on the specific requirements for your project during a free consultation.