Work out a realistic cost range for a loft conversion or house extension before you get quotes. Choose your project type and enter the floor area it will add.
Estimate only, based on typical UK per-m² rates for each project type. Smaller lofts and extensions carry a higher rate per m² since fixed costs (architect, structural steels, staircase or foundations) are spread over less floor area. For a double-storey extension, enter the combined floor area added across both floors. Loft conversions above a certain size and most extensions also need building regulations approval, and larger or non-permitted-development projects need planning permission — always confirm requirements and get multiple itemised quotes from local builders before budgeting exactly.