Home Extension Design in Richmond upon Thames: Planning, Costs and What's Realistic in 2026

A home extension in Richmond upon Thames typically costs £3,200 to £4,500 per m² to build in 2026, at mid-range specification, before VAT and professional fees. Planning is the real story here: the borough has 72 conservation areas, more coverage than almost anywhere in London, and dozens of street-level Article 4 Directions that can remove permitted development rights for even small extensions. Two identical houses a street apart can face completely different rules. This page covers what the council allows, what it costs, and how to check before you design.

Studio MASS is a residential design practice led by an architectural technologist. We design and deliver extensions, loft conversions and refurbishments across London, from first feasibility check to completed build.

Do you need planning permission for an extension in Richmond upon Thames?

Assume nothing in this borough until your street has been checked. Outside conservation areas, a single-storey rear extension up to 3 metres beyond the original rear wall (4 metres on a detached house) usually falls under permitted development. Inside the borough's 72 conservation areas, side extensions and rear extensions beyond 3 metres, along with any multi-storey rear extension, need planning permission.

Richmond goes further than most boroughs. The council maintains a long register of Article 4 Directions tied to individual streets and terraces, from Archway Street in Barnes to Cambridge Cottages in Kew, Petersham, Ham Street and dozens more. Where one applies, planning permission is needed for work that is normally permitted, including small extensions and additions, new doors and windows, painting or rendering brickwork, removing chimneys, and replacing front gardens or boundary walls.

The practical rule: the council publishes the full register and maps online, and checking your address against them is the first task of our Stage Zero review, before any design work starts.

What kind of homes are we extending in Richmond upon Thames?

Richmond's housing stock is unusually varied for one borough. Barnes and Kew hold Georgian and Victorian cottages and villas on tight, protected streets. Richmond itself and East Sheen mix Victorian and Edwardian terraces with substantial semis. Across the river, Twickenham, Teddington and Hampton run from riverside terraces to broad interwar family houses with deep gardens.

The brief differs by house type. Period cottages in Kew or Barnes usually need careful, material-matched rear additions designed around Article 4 constraints. Edwardian terraces in East Sheen and St Margarets suit side-return kitchen extensions. The interwar semis of Teddington, Hampton and Whitton are the borough's best loft-conversion stock, often with room for a rear extension as well.

How much does a home extension cost in Richmond upon Thames in 2026?

Richmond sits in London's mid-price construction zone by travel band, though its period stock often pushes budgets toward the top of the range. From our 2026 Extension Cost Guide, built from BCIS indices, FMB build cost data and our own completed projects:

A single-storey extension in Richmond upon Thames costs £3,200 to £4,500 per m² at mid specification in 2026. A loft conversion runs £3,200 to £3,800 per m². Conservation area projects, which in this borough means a large share of all projects, carry roughly 15% on top for material restrictions and period-appropriate detailing. These figures are construction only; VAT at 20% and professional fees are additional.

Before a brick is laid, expect £8,000 to £16,000 in professional and statutory fees on a typical project, including the £548 planning application fee that applies from April 2026.

The full breakdown by extension type and specification level is in our free Extension Cost Guide 2026, no email required. To see how we design and deliver this kind of work, with real budgets attached, have a look at the Rathcoole Gardens project page and the Drakefield House project page, two completed London projects.

Who designs your extension if not an architect?

An architectural technologist designs buildings with a focus on how they are built: construction detail, building regulations, and buildability, alongside layout and light. In the UK "architect" is a legally protected title, so we don't use it. What matters for a Richmond extension is the same either way: design within the local planning context, technical drawings a builder can price accurately, and someone accountable from first idea to finished build. That is what we do, through one team and five stages, starting with a Stage Zero review that tells you what is realistic for your budget and what planning will allow before design begins.

Start with a conversation

The best starting point is our short questionnaire. It takes a few minutes and tells us about your home, your brief and your budget. We review it and arrange a free thirty-minute call, with an honest view on feasibility either way.

Start Here →