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 Hackney
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 Hackney are listed below, taken from our Hackney area page. Each one is a reason to confirm the address on Hackney's constraints map before relying on permitted development.
- Conservation areas. Hackney has around 30 conservation areas, including De Beauvoir, Clapton Square, Stoke Newington, Clissold Park, Cazenove, Graham Road and Mapledene, and South Shoreditch. Roof extensions are not permitted development inside them, and each area has an appraisal that officers apply to extensions and dormers. Source
- Article 4 directions. Hackney has Article 4 directions in several conservation areas removing permitted development for front alterations, boundary walls and some roof works, and a direction restricting office-to-residential conversions under Class MA in Shoreditch and other employment areas. Check the council's constraints map before relying on permitted development or prior approval. Source
- Lee Valley flood risk. Hackney Wick, Lea Bridge, Upper and Lower Clapton along the River Lee and the Hackney Marshes edge sit in Flood Zones 2 and 3. Ground-floor extensions and basements there may need a flood risk statement. Source
- Listed buildings. Clapton Square, Sutton Place, Stoke Newington Church Street and parts of Shoreditch and De Beauvoir contain a high concentration of listed houses. Listed building consent is needed for almost any alteration, internal or external. Source
What Hackney planning officers look for
Hackney officers are firm on the character of terrace rear elevations and roofs. Common refusal reasons are rear extensions deeper or taller than the neighbours that fail the 45-degree test, roof extensions in conservation areas that break an unbroken roofline, full-width box dormers, and front dormers. Mansards are usually accepted only where the terrace already has them. Outside conservation areas, rear dormers within 40 m³ are routinely lawful. Hackney offers a paid pre-application service and we recommend it for anything in a conservation area. Decisions often run past the statutory 8 weeks; allow 10–14 weeks.
Fees and timelines
The council fee for a householder application is £528 and for a Lawful Development Certificate £264 (England, from 1 April 2025; verify before applying). Both are decided within 8 weeks of validation.
Our own fee for the drawings and the application is fixed once quoted and depends on the project type, its size and the constraints above. Answer six questions in the quote tool and we email you an indicative figure within minutes, then a written fixed-fee quote within 24 hours.
