Kitchen Extension Cost in Brentford: 2026 Price Guide

A single-storey rear kitchen extension is one of the most popular projects among homeowners in Brentford, where Georgian and Victorian cottages along the historic High Street and waterfront, alongside the new-build apartment blocks that have gone up as part of the Brentford riverside regeneration. It's usually the difference between a cramped galley kitchen and a proper kitchen-diner opening onto the garden.

Typical costs

• Small extension (up to 15m²): roughly £30,000-£45,000
• Medium extension (15-25m²): roughly £45,000-£70,000
• Larger or wraparound extension (25m²+): £70,000 upwards

These figures are a guide, not a quote - they cover building work, a standard fit-out, and typical finishes. Bifold or sliding doors, roof lanterns, underfloor heating and a higher-spec kitchen will all add to the total.

What affects the price locally

In Brentford, the biggest local factor is usually access. Many streets are close terraces with no side access, which means materials have to be carried through the house and skips have to sit on the road - both of which builders will price in. Properties within the Brentford High Street and Brentford Ait conservation areas sometimes face tighter controls on matching brick, roofline and window styles to the existing building, which can add to material costs even for a rear extension that doesn't need planning permission.

Foundations are the other variable: older Victorian and Edwardian houses near the confluence of the River Brent and the Thames, and the Gtech Community Stadium were often built on shallow footings, so a structural engineer may specify deeper or more extensive foundations than a newer property would need.

Do you need planning permission?

Many single-storey rear extensions fall under permitted development, but there are limits on how far you can extend without full planning permission, and those limits are usually tighter for terraced and semi-detached houses than detached ones. If your home is in one of Brentford's conservation areas, permitted development rights can be restricted further, so it's worth checking with the London Borough of Hounslow's planning department - or a builder who works in the area regularly - before you commit to a design.