How much does a house extension cost in the UK? (2026)
The cost of a house extension in the UK typically ranges from £27,000 to £160,000 depending on size, type, and specification. A typical single-storey rear extension of 20–25 m² at mid specification costs around £48,000–£65,000 fully built — including structure, glazing, roofing, and fit-out.
Prices per square metre range from around £1,800/m² for a basic single-storey rear extension to over £4,200/m² for a premium wrap-around. London and the South East typically adds 20–25% to these figures.
What drives the cost of a house extension?
The single biggest cost factor is specification — particularly the quality of glazing and kitchen/bathroom fit-out. Aluminium bi-fold doors can cost £3,000–£8,000 for a single run, and a bespoke kitchen can add £15,000–£40,000 above a standard alternative.
Location also has a significant impact. Labour costs in London are typically 25% higher than the rest of England, and materials delivery can add further. Structural complexity — particularly for wrap-around and double-storey extensions — increases both materials and labour costs due to the steelwork involved.
How to get the best price for your extension
Getting at least three quotes from local, reputable builders is the most effective way to ensure you pay a fair price. Prices for the same project can vary by 20–40% between different contractors. Be cautious of quotes that are significantly lower than others — these can indicate corners being cut on materials or labour.
Post your extension job on GetQuickHelp and get contacted by vetted local builders — free, with no obligation to accept any quote.