Working out the cost of an extension in Birmingham is rarely a single number, because so much depends on size, ground conditions and finish. This guide gives realistic 2026 ranges for the West Midlands and explains what actually moves the price, so you can budget before you ring round for quotes.
For the Birmingham and wider West Midlands area, a straightforward single-storey rear extension usually lands somewhere between £1,800 and £2,600 per square metre for the build itself. A double-storey extension often works out cheaper per square metre, roughly £1,600 to £2,300, because you are paying once for foundations and roof while gaining two floors.
As a rough total, a modest 15 square metre kitchen extension might sit around £30,000 to £45,000, while a larger wraparound can comfortably pass £70,000 once kitchens, glazing and finishes are included.
The brickwork and groundworks are where Birmingham sites vary most. Matching existing Victorian or 1930s brick across Moseley, Kings Heath or Selly Oak can mean sourcing reclaimed stock, which costs more than standard facing bricks. Clay-heavy ground in parts of the city, or nearby trees, can push foundations deeper and add to the cost before a single wall goes up.
Access matters too. A terraced property with no side gate means materials and muck go through the house, which slows the work and raises labour. Drains, manholes and the need for a build-over agreement with Severn Trent can also add time and fees.
It helps to see roughly how a budget splits, because the headline figure hides a lot. Brickwork and structure are a major share, but glazing, kitchens and bathrooms often surprise people most.
Beyond the builder's quote, set aside money for design and approvals. Structural engineer calculations are usually needed for steel beams, and Building Control sign-off applies to almost every extension. Planning permission is not always required thanks to permitted development, but a lawful development certificate is still worth having when you sell.
Typical extra costs include architectural drawings from around £1,200 to £3,000, a structural engineer from £400 to £900, and Building Control fees of several hundred pounds. A party wall agreement, common on terraced and semi-detached homes, can add more if a surveyor is involved.
Most single-storey extensions in Birmingham take around 10 to 16 weeks on site, though groundworks delays, bad weather or bespoke glazing can extend that. Getting drawings and approvals sorted first keeps the build moving.
Many extensions fall under permitted development and do not need full planning permission, but limits on size, height and proximity to boundaries apply, and conservation areas are stricter. It is always worth checking with Birmingham City Council before starting.
Big gaps usually come down to what is included, such as foundations depth, brick matching, glazing quality and whether finishes are in the figure. Ask for an itemised breakdown so you are comparing genuinely like for like.
Tell us a few details about what you're planning. We'll come back within 24 hours, usually the same day, and get a site visit booked in for the week.
Most jobs start with a 5-minute call so we can work out if we're the right fit and when we could realistically get on site. No hard sell.