Extensions and loft conversions in Sevenoaks
Sevenoaks is a district of towns and villages set inside the Green Belt and, across the North Downs, the Kent Downs National Landscape. In Sevenoaks town, Kippington and Wildernesse the large detached and Edwardian houses take two-storey rear and side extensions, full remodels and hip-to-gable lofts. In Swanley, Hextable and Dunton Green the 1930s and post-war semi dominates, and the typical project is a two-storey side extension over the garage, a 4–6 m rear extension, a hip-to-gable loft with a rear dormer, or a garden room. In Westerham, Otford, Kemsing, Shoreham and Edenbridge the cottages and timber-framed houses are often listed or in a conservation area, and the work is careful single-storey extension and internal alteration.
Where the house is outside a conservation area and outside the Kent Downs, much of this is permitted development (PD) and we secure a Lawful Development Certificate (LDC) as proof. PD still applies to houses in the Green Belt, which covers most of the district, but anything that needs planning permission there has to pass the Green Belt test described below. Inside the Kent Downs PD is tighter, and in the district’s conservation areas roof extensions lose PD rights, so a planning application designed to the character appraisal is the norm. New Ash Green’s Span-style houses carry estate design controls on top of planning. Flats have no householder PD rights at all.
Planning constraints in Sevenoaks
- Green Belt across most of the district outside the main built-up areas, where extensions must stay proportionate to the original house and outbuildings face a stricter test.
- Kent Downs National Landscape across the North Downs, including Otford, Kemsing, Shoreham and Westerham, where PD is tighter and landscape impact is weighed.
- Around 40 conservation areas, including Sevenoaks High Street and The Vine, Westerham, Otford, Kemsing, Shoreham, Edenbridge and Riverhead, where roof extensions lose PD rights; check the council’s constraints map for the exact boundaries.
- Knole Park and listed buildings throughout the town and villages.
- River Darent and River Eden flood risk through Westerham, Riverhead, Otford, Shoreham and Edenbridge.
- New Ash Green estate controls on external alterations, alongside planning.
What Sevenoaks planning officers look for
Officers assess householder applications against the Core Strategy 2011, the Allocations and Development Management Plan 2015 and the council’s residential extensions guidance. They look for extensions that stay subordinate to the original house; side extensions set back from the front elevation and down from 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 that are subordinate, set back from the eaves and clad in matching tile.
In the Green Belt the key test is that an extension must not be disproportionate to the original dwelling, meaning the house as first built or as it stood on 1 July 1948, counting every extension added since. Officers usually measure this by floorspace and volume, and the council’s guidance has historically treated additions beyond about half the original as needing a strong case, so we measure carefully before designing. Outbuildings are treated as new buildings in the Green Belt and face a stricter test than extensions, so garden rooms that need permission should stay modest and close to the house; where PD applies we use the LDC route instead. In the Kent Downs officers look for roof forms and materials that sit quietly in the landscape. Disproportionate Green Belt additions, terracing effects and box dormers in conservation areas are the standard refusals. Sevenoaks offers paid pre-application advice. Council fees from April 2025 are £528 for a householder application and £264 for a proposed-use LDC; verify before applying.
Our services in Sevenoaks
- Planning documentation
- House extensions – rear, side and two-storey extensions on detached houses and semis
- Loft conversions – hip-to-gable and rear dormer lofts
- Permitted development and LDCs
- Outbuildings and garden rooms – including Green Belt plots
- Feasibility studies and pre-application advice – for Green Belt, Kent Downs and listed building work
- Building Regulations drawings
Example projects nearby
- Garden office in Bromley – 20 m² garden office under permitted development in a neighbouring borough
- Two-storey extension in Ealing – two-storey rear extension and side infill on an inter-war semi, the same house type as Swanley and Hextable
- Loft conversion in Richmond upon Thames – hip-to-gable and rear dormer on an Edwardian semi in a conservation area
Guides
Read Permitted development rights in London and Pre-application advice from your council.
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