How deep can I extend without planning permission?

Three metres from the original rear wall on a terraced or semi-detached house and four metres on a detached house, under Class A permitted development. Six or eight metres is possible through the larger home extension prior approval, a 42-day process with a £120 fee, outside conservation areas.

Do I need a Lawful Development Certificate if the extension is permitted development?

Not legally, but we recommend one. It is the council's formal confirmation that the extension is lawful, which lenders, buyers and solicitors routinely ask for. The fee is £264 and the decision takes up to 8 weeks.

What if my neighbour has already extended?

Their extension does not change your rights, but it does shape what the council will accept if you need planning permission: officers compare depth and height against the neighbouring extension and apply the 45-degree daylight test from the nearest habitable window.

How long does Tower Hamlets take to decide?

The statutory period is 8 weeks from validation for both a householder application and a Lawful Development Certificate, and 42 days for a larger home extension prior approval. Decisions often run past the statutory 8 weeks; allow 10–14 weeks.

Rear Extensions in Tower Hamlets: Planning

Rear extensions in Tower Hamlets depend on the house. Typical homes here: Victorian terraces in Bow, Mile End, Stepney Green, Bethnal Green and Globe Town; Georgian and early Victorian houses around Tredegar Square, Stepney Green and Spitalfields. Designations to check first: Conservation areas; Article 4 directions; Thames and Lea flood risk. Applications are decided by London Borough of Tower Hamlets and the Tower Hamlets Local Plan 2031.

The permitted development rules for rear extensions

On a house, a single-storey rear extension is permitted development if it projects no more than 3 m from the original rear wall on a terraced or semi-detached house, or 4 m on a detached house, is no higher than 4 m, has eaves no higher than 3 m where it comes within 2 m of a boundary, and uses materials similar in appearance to the house. The larger home extension route allows 6 m or 8 m through a 42-day prior approval, where the council consults the neighbours.

Flats and maisonettes have no householder permitted development rights, so any rear extension to a flat needs planning permission. Previous extensions count against the allowance, and the larger home extension route is not available in conservation areas.

What changes in Tower Hamlets

In a conservation area a single-storey rear extension can still be permitted development within the 3 m or 4 m limit, but cladding it in materials that differ from the house is not, and the 6 m and 8 m prior approval route is closed.

The local constraints that most often decide the route in Tower Hamlets are listed below, taken from our Tower Hamlets area page. Each one is a reason to confirm the address on Tower Hamlets' constraints map before relying on permitted development.

Conservation areas. Tower Hamlets has more than 50 conservation areas, including Tredegar Square, Victoria Park, Driffield Road, Medway, Stepney Green, Fournier Street and Brick Lane, Wapping Pierhead and Narrow Street. Source
Article 4 directions. The council has Article 4 directions removing office-to-residential permitted development (Class MA) in the City Fringe, Canary Wharf and other employment areas, and directions in several conservation areas limiting front alterations and roof works. Source
Thames and Lea flood risk. Much of the borough south of Commercial Road and along the River Lea, including Wapping, Limehouse, the Isle of Dogs, Poplar and Blackwall, is Flood Zone 3, defended by the Thames Barrier and river walls. Source
Listed buildings. Spitalfields, Stepney Green, Tredegar Square and the riverside at Wapping and Limehouse contain a high concentration of listed houses and warehouses. Source

What Tower Hamlets planning officers look for

Tower Hamlets officers assess householder applications against Local Plan 2031 policies on design and amenity and the conservation area character appraisals. On the terraces of Bow and Bethnal Green they expect rear extensions to sit below the neighbour's first-floor sill and clear the 45-degree line, side-return infills with a lightweight glazed roof against the party wall, and mansards only where the terrace already has a mansard precedent, set back behind the front parapet with traditional dormers. Common refusal reasons are full-width box dormers, roof extensions that break an unbroken roofline in a conservation area, and rear extensions deeper than the established pattern. The council offers paid pre-application advice and we recommend it for conservation area roof work.

Fees and timelines

Tower Hamlets decides a householder application or a Lawful Development Certificate within 8 weeks of validation. The council fee is £528 for a householder application and £264 for a Lawful Development Certificate (England, from 1 April 2025; verify before applying).

Our own fee is fixed once quoted. The quote tool gives an indicative figure in minutes and a written quote follows within 24 hours.

Primary sources

The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2: the permitted development limits quoted above.
Planning Portal: do you need permission: the national guidance and the application service every council accepts.
London Borough of Tower Hamlets: planning: the council's own constraints map, validation checklist and pre-application service.

Do I need planning permission for a rear extension in Tower Hamlets?