Lofts in the Sevenoaks district fall into three groups, and the group decides the route before any drawing starts. In Swanley, Hextable and Dunton Green the 1930s and post-war semis take a rear dormer, often with a hip-to-gable end, and many are permitted development. In Sevenoaks town, Kippington and Riverhead the larger Edwardian and detached houses have deep roof spaces but are more likely to sit in a conservation area. In Otford, Kemsing, Shoreham and Westerham the house is often listed, in a conservation area or in the Kent Downs, and a roof extension is rarely permitted development.
The permitted development rules for loft conversions
A loft conversion with a rear dormer is permitted development on a house if the added roof volume is no more than 40 m³ on a terraced house or 50 m³ on a semi-detached or detached house, the dormer sits at least 200 mm back from the eaves and no higher than the ridge, there is no dormer on the roof slope facing the road, materials are similar in appearance, and side windows are obscure-glazed.
Flats and maisonettes have no permitted development rights, so a loft to a top-floor flat always needs planning permission. Full-width box dormers that reach the ridge, and hip-to-gable conversions on semis whose volume exceeds 50 m³, also fall outside the allowance.
What changes in Sevenoaks
Roof extensions are not permitted development in a conservation area, so a dormer or hip-to-gable there needs a householder planning application designed to the area's appraisal.
The local constraints that most often decide the route in Sevenoaks are listed below, taken from our Sevenoaks area page. Each one is a reason to confirm the address on Sevenoaks' constraints map before relying on permitted development.
- Green Belt. Most of the Sevenoaks district outside the built-up areas of Sevenoaks town, Swanley, Westerham, Edenbridge and the larger villages is Metropolitan Green Belt. Source
- Kent Downs National Landscape. The Kent Downs National Landscape (formerly the Kent Downs AONB) covers the North Downs across much of the district, including Otford, Kemsing, Shoreham, Westerham and the countryside north of Sevenoaks town. Source
- Conservation areas. Sevenoaks has around 40 conservation areas, including Sevenoaks High Street and The Vine, Westerham, Otford, Kemsing, Shoreham, Edenbridge, Riverhead, Chevening and many smaller village centres. Source
- Knole Park and listed buildings. Knole House and its deer park sit on the edge of Sevenoaks town, and the town, Westerham, Otford, Shoreham, Edenbridge and the villages contain a very high concentration of listed houses, cottages and churches. Source
- River Darent and River Eden flood risk. The River Darent runs from Westerham through Riverhead, Otford and Shoreham, and the River Eden runs through Edenbridge; land alongside both sits in Flood Zones 2 and 3. Source
How the Green Belt treats a loft conversion in Sevenoaks
Most of the district is Green Belt, where the council's Green Belt guidance caps total additions at 50% of the floorspace of the "original" dwelling, measured externally. The original dwelling is the house as first built or, for older homes, as it stood on 1 July 1948, and every later extension counts towards the 50%.
The guidance treats lofts differently from other extensions. A conversion that adds only roof lights is permitted and does not count towards the 50%, provided it adds no volume or bulk. A conversion with dormer windows, or any other alteration that creates volume or bulk, does count. On a Green Belt house that has already been extended, a rear dormer can be what pushes the total over the line, so we measure the original floorspace before choosing between roof lights and a dormer.
What the council's extensions guidance expects of a dormer
Sevenoaks' Residential Extensions guidance asks that a loft extension stays below the ridge of the existing roof, is set back at least 20 centimetres from the eaves and sides, and follows the vertical lines of the doors and windows below. It prefers loft extensions on the back of the house, and says new dormers will not normally be allowed on a front elevation in a street where there are none already, with roof lights as the preferred alternative.
It also says that where a dormer or roof extension needs planning permission, one that is disproportionate to the house, or that causes unacceptable overlooking of a neighbour, will not be allowed. On 1930s hipped roofs and 19th-century terraces with a common roof line, it asks that a loft does not detract from the street's characteristic roof profile.
What Sevenoaks planning officers look for
They tend to look for extensions that stay subordinate to the original house in scale and roof form, side extensions set back from the front wall and below the ridge with a gap kept to the boundary, rear extensions that clear the 45-degree line to the neighbour's nearest habitable window, and dormers set back from the eaves and clad in matching tile. In the Kent Downs they look for materials and roof forms that sit quietly in the landscape. Common refusal reasons are disproportionate Green Belt additions, side extensions that create a terracing effect, and roof extensions or box dormers in conservation areas. Outside the designations, hip-to-gable and rear-dormer lofts within 50 m³ on a semi are routinely lawful and we secure a Lawful Development Certificate as proof.
Fees and timelines
Sevenoaks 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
- Sevenoaks District Council: Development in the Green Belt SPD (2015)
- Sevenoaks District Council: Residential Extensions SPD (2009)
- GOV.UK: Party Wall etc. Act 1996 guidance
- 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.
- Sevenoaks District Council: planning: the council's own constraints map, validation checklist and pre-application service.
