What Does a Kitchen Extension Cost in the UK?
A kitchen extension is one of the most transformative improvements you can make to a home. The budget needs to account for far more than just the bricks and mortar. A typical single-storey rear extension costs £1,500 to £2,500 per square metre for the structure alone. For a 20 sqm extension, that's £30,000 to £50,000 before kitchen fitting — add a new kitchen and the total often lands between £50,000 and £100,000 for a high-quality result.
Cost Breakdown
Building the Extension
- Foundations and groundworks: £3,000 to £8,000
- Brickwork and structure: £15,000 to £30,000 (20 sqm)
- Roof: £5,000 to £15,000 depending on type
- Windows and bi-fold doors: £3,000 to £12,000
- Insulation, plastering, flooring finish: £4,000 to £8,000
- Electrics and heating: £2,000 to £5,000
New Kitchen
- Budget fitted kitchen: £3,000 to £7,000
- Mid-range kitchen: £8,000 to £20,000
- Premium kitchen: £20,000 to £50,000+
- Installation labour: £2,000 to £5,000
Professional Fees
An architect or architectural designer is needed for most extensions — expect to pay £1,500 to £5,000 for drawings and planning support. Planning application fees are £206 for a householder application. A structural engineer typically adds £500 to £1,500.
Planning Permission and Permitted Development
Many single-storey rear extensions fall under Permitted Development rights. For detached houses, the maximum depth is 8 metres; for terraced and semi-detached, 6 metres. Building Regulations approval is always required even under Permitted Development.
Key Cost Drivers
- Extension size
- Roof complexity — glass roofs cost significantly more than flat roofs
- Glazing — bi-fold or sliding door sets add £5,000 to £15,000
- Kitchen specification — this is where budgets most often overrun
- Location — London and South East are 30 to 50 per cent more expensive than the Midlands or North