London price guide
House extension quotes in London
Typical local pricing runs £2,250–£3,700 per m² of new floor area, excluding VAT and kitchen fit-out. Here is what drives that range in London, and what to check on the quotation in front of you.
Indicative London range
£2,250 – £3,700
per m² of new floor area, excluding VAT and kitchen fit-out. Based on a local cost index of 1.28 against the UK average.
Why London pricing differs
The deepest contractor market in the UK and the most expensive. Good builders are booked six to nine months ahead and rarely need to compete on price.
Victorian and Edwardian terraces, converted flats and post-war blocks, with side returns and rear extensions the most common projects.
Planning and consent
Thirty-two boroughs with markedly different policies, extensive conservation areas and frequent Article 4 directions removing permitted development rights.
What to check on a house extension quotation
- Foundation depth allowed for, and the rate if a deeper dig is needed
- Whether structural steel, engineer's fees and building control are inside the price
- The glazing allowance, stated per m² or per unit
- Which items are provisional sums rather than fixed prices
Areas we see quotes from
Homeowners across Clapham, Islington, Ealing, Walthamstow, Wandsworth and the wider Greater London area use KnowMyQuote to understand what a contractor has actually priced before committing.
Frequently asked questions
How much does house extension work cost in London?
Local pricing typically runs £2,250–£3,700 per m² of new floor area, excluding VAT and kitchen fit-out, based on a higher-than-average cost index of 1.28 for London.
Why do quotes in London differ so much?
Because they rarely cover the same scope. The deepest contractor market in the UK and the most expensive. Good builders are booked six to nine months ahead and rarely need to compete on price. Two quotes for the same job can exclude different items, which is why comparing exclusions matters more than comparing totals.
Do I need planning permission in London?
Thirty-two boroughs with markedly different policies, extensive conservation areas and frequent Article 4 directions removing permitted development rights. Always confirm with the local authority before committing, and apply for a Lawful Development Certificate where the work is permitted development.
How many quotes should I get?
Three, all priced against the same drawings and written specification. Without a common document you are comparing three different buildings, not three prices.
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