Calculate your build cost
Select your main project below. For an extension or loft conversion, you can also include refurbishment of the existing house, with a separate floor area and finish.
Free 2026 guide-range estimator for London and the South East
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Free calculator · updated September 2026Select your main project below. For an extension or loft conversion, you can also include refurbishment of the existing house, with a separate floor area and finish.
This is an early budgeting guide, not a quotation. The result excludes VAT, professional fees, statutory charges, surveys, structural engineering, Party Wall matters, specialist reports, abnormal site conditions and major structural alterations to the existing house. Area allowances include general building work and internal finishes; kitchen and bathroom fit-outs are added only through the quantities above. Refurbishment assumes renewal of internal finishes and services. The estimate range reflects pricing uncertainty; allow separately for a project contingency.