Rear extensions in Kensington and Chelsea depend on the house. Typical homes here: Stucco and brick terraces and garden squares in Kensington, Chelsea, Notting Hill and Earl's Court; Mews houses behind the main terraces across Kensington, Belgravia-edge Chelsea and Notting Hill. Designations to check first: Conservation areas; Basement Article 4 direction and basement policy; Listed buildings. Applications are decided by Royal Borough of Kensington and Chelsea and the Kensington and Chelsea Local Plan.
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 Kensington and Chelsea
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 Kensington and Chelsea are listed below, taken from our Kensington and Chelsea area page. Each one is a reason to confirm the address on Kensington and Chelsea's constraints map before relying on permitted development.
- Conservation areas. Conservation areas cover about three quarters of Kensington and Chelsea, so almost every house in the borough is inside one. Source
- Basement Article 4 direction and basement policy. The council has an Article 4 direction removing permitted development for basement excavations across the borough, and its Local Plan basement policy limits new basements to a single storey beneath the house and no more than half the garden, with structural, drainage, construction traffic and neighbour-impact information required. Source
- Listed buildings. Kensington and Chelsea has thousands of listed buildings, including whole terraces and squares in Kensington, Chelsea and Notting Hill.
- Article 4 directions on external alterations. Several conservation areas carry Article 4 directions removing permitted development for front alterations, painting, windows, roofs and boundary treatments.
- Thames flood zone. Chelsea Embankment, Cheyne Walk and the riverside streets fall within Flood Zones 2 and 3, protected by the Thames Barrier and river walls. Source
What Kensington and Chelsea planning officers look for
Officers expect extensions to be subordinate, to follow the established pattern on the terrace and to use matching materials and traditional detailing; rear extensions that rise above the closet wing, roof extensions on terraces with unbroken rooflines and any front-elevation change are commonly refused. Pre-application advice is available for a fee and we recommend it for almost every project in the borough.
Fees and timelines
Kensington and Chelsea 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.
- Royal Borough of Kensington and Chelsea: planning: the council's own constraints map, validation checklist and pre-application service.
