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 Kingston upon Thames
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 Kingston upon Thames are listed below, taken from our Kingston upon Thames area page. Each one is a reason to confirm the address on Kingston upon Thames's constraints map before relying on permitted development.
- Conservation areas. Kingston has numerous conservation areas, including Kingston Old Town, Surbiton's Southborough and Oakhill areas, Coombe and parts of New Malden. Roof extensions and cladding in these areas need planning permission. Check the council's constraints map for your address before relying on permitted development. Source
- Thames and Hogsmill flood zones. Land along the Thames at Kingston and Canbury and along the Hogsmill through Old Malden, Berrylands and Kingston falls within Flood Zones 2 and 3. Basements and new ground-floor habitable rooms may need a flood risk assessment even for a householder application. Source
- Green Belt and Metropolitan Open Land. Chessington, Hook and the southern edge of the borough include Green Belt, and there is Metropolitan Open Land along the Hogsmill and around Richmond Park. Extensions and outbuildings to houses within or adjoining these areas are judged on openness and are often limited in size.
- Article 4 directions. Some Kingston conservation areas are understood to carry Article 4 directions removing permitted development for front alterations and boundary treatments. Coverage varies by area, so we confirm with the council before recommending a permitted development route.
What Kingston upon Thames planning officers look for
Kingston is a predominantly suburban borough and its officers pay close attention to the character of 1930s streets. Side extensions that close the gap between semis, are not set back from the front wall or carry a roof up to the main ridge are a frequent refusal reason, as are two-storey rear extensions that breach the 45-degree rule to neighbours. Single-storey rear extensions of 3 to 4 m are generally acceptable. Roof extensions in conservation areas and front dormers anywhere attract resistance. Pre-application advice is available for a fee.
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.
