Kitchen Extension Cost in Brentford: 2026 Price Guide

Ask a local builder what the most common job in Brentford is, and a rear kitchen extension is usually near the top of the list - understandable given 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 across much of the area. Most homeowners are chasing the same thing: a proper kitchen-diner instead of a cramped galley kitchen.

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

Access is usually what separates a straightforward Brentford quote from an expensive one. Terraces without a side passage mean everything - materials in, spoil out - goes through the house, and builders price that in accordingly. Add to that the Brentford High Street and Brentford Ait conservation areas, where matching brick, roofline and window detailing to the existing building is typically expected even for extensions that wouldn't otherwise need planning permission.

Don't overlook foundations either: much of the older housing stock close to the confluence of the River Brent and the Thames, and the Gtech Community Stadium sits on shallow Victorian or Edwardian footings, which a structural engineer will often want to deepen or extend before an extension can be signed off.

Do you need planning permission?

Permitted development covers a lot of single-storey rear extensions, but not without limits, and those limits bite harder on terraced and semi-detached houses than detached ones. Inside Brentford's conservation areas, expect those rights to be trimmed back further still - check with the London Borough of Hounslow's planning department, or a builder who already works locally, before finalising a design.