Home Extension Design in Tower Hamlets: Planning, Costs and What's Realistic in 2026
A home extension in Tower Hamlets typically costs £4,000 to £5,500 or more per m² to build in 2026, at mid-range specification, before VAT and professional fees. Planning depends heavily on where you are: the borough has 58 conservation areas, taking in most of its Victorian terrace streets around Bow, Mile End and Bethnal Green. There is good news too. The council has adopted mansard roof extension guidelines in five conservation areas, opening a route to roof extensions that were previously discouraged. This page covers the rules, the costs, and how to check your street.
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 Tower Hamlets?
The answer usually comes down to two questions: is your home a house or a flat, and is it in one of the borough's 58 conservation areas. Flats have no permitted development rights, so external changes need planning permission regardless of location. For houses outside conservation areas, a single-storey rear extension up to 3 metres beyond the original rear wall usually falls under permitted development. Inside a conservation area, side extensions and rear extensions beyond 3 metres, along with any multi-storey rear extension, need planning permission.
Roof extensions have their own local story. The council has adopted design guidelines for mansard roof extensions in five conservation areas, Clinton Road, Driffield Road, Medway, Ropery Street and Tredegar Square, giving residents a clearer path to consent. Proposals must follow the design guidance, include improvements to the front of the house, and make a financial contribution to a streetscape improvement fund. A borough-wide Article 4 Direction also removes the right to convert a house to a small HMO without permission, in force since January 2021.
Checking your address against the council's conservation area map, and whether the mansard guidelines cover your street, is part of our Stage Zero review before any design work starts.
What kind of homes are we extending in Tower Hamlets?
Most Tower Hamlets homes are flats, but the borough keeps a substantial stock of period houses. Bow and Mile End hold long runs of flat-fronted Victorian terraces around Tredegar Square, Driffield Road and Medway. Bethnal Green mixes terraces with the tight cottage streets of the Jesus Hospital Estate. Stepney Green has genuine Georgian houses, and Wapping and Limehouse trade in warehouse conversions along the river.
The classic brief in Bow is a rear extension into the yard plus, where the guidelines allow, a mansard roof extension behind the parapet, which can add a full storey to a two-storey terrace. Georgian and listed properties in Stepney Green need a more conservative hand. For flats and conversions, the work is usually internal: reconfiguration, light and storage rather than added floor area.
How much does a home extension cost in Tower Hamlets in 2026?
Tower Hamlets sits in London's inner-price construction zone. From our 2026 Extension Cost Guide, built from BCIS indices, FMB build cost data and our own completed projects:
A single-storey extension in Tower Hamlets costs £4,000 to £5,500 or more per m² at mid specification in 2026. A loft conversion runs £3,200 to £3,800 per m². Conservation area projects, which covers most terrace streets in Bow and Bethnal Green, carry roughly 15% on top for material restrictions and period-appropriate detailing, and mansard schemes carry the streetscape fund contribution as well. 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 Tower Hamlets 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.
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