House Extension Cost in Richmond: 2026 Price Guide

Beyond the kitchen-focused rear extension, many homeowners in Richmond look at side-return infills or full double-storey extensions to add real square footage without moving house - particularly on the terraced streets where a side return is otherwise wasted space.

Typical costs

• Side return infill: roughly £25,000-£40,000
• Single-storey rear extension: roughly £35,000-£70,000
• Double-storey extension: roughly £70,000-£130,000+

A double-storey extension isn't simply double the cost of a single-storey one - the roof, foundations and scaffolding are a large fixed cost, so the additional storey is often better value per square metre.

What affects the price locally

A significant part of Richmond falls inside the Richmond Hill conservation area - the borough has 85 in total, one of the highest counts of any London borough, part of the London Borough of Richmond upon Thames's wider planning area - which shapes both what's permitted and what materials are expected. Matching original brick, slate or stone detailing here usually costs more than a standard modern finish, and tends to add time to the planning process as well.

Access is again a factor on the tighter terraced streets: scaffolding, skips and material deliveries on narrow roads near Richmond Park and Richmond Hill often need council permits, which a local builder will usually have already dealt with before.

Planning permission

Side return and single-storey rear extensions often qualify for permitted development if they stay within set size limits, but double-storey extensions almost always need full planning permission from the London Borough of Richmond upon Thames. Get a pre-application check if your street falls within a conservation area - it's a small upfront cost that can save a redesign later.