House extensions in Sevenoaks

Single storey or two storey?

The 2021 Census recorded 33.1% of Sevenoaks homes as detached, 28.7% as semi-detached and 22.4% as terraced. With a third of houses standing in their own plots, many owners have a genuine choice between going out and going up. A single storey rear extension keeps the work at ground level and suits a kitchen, dining or family room. A two storey addition costs more per project but adds space on both floors from one set of foundations.

On a semi the decision often comes down to the neighbour's side and how a raised wall would affect their light. On a detached house the side plot can open up a wing that does not touch the boundary at all. We sketch both options against the existing roof line before anyone commits to drawings.

We hear from owners in Riverhead, Kippington, Wildernesse, St John's, Chipstead, Dunton Green and Seal, and the house types vary a lot between them, so the brief is always taken from the property itself.

Ground conditions and foundations

Sevenoaks sits where routes climb over the Greensand Ridge, and the old London road was turnpiked in 1709 because of the clay soils. That history is a useful reminder that ground in the area can vary over short distances. Trial holes and the ground found when the trenches are dug tell us what the foundation needs, and building control inspects the excavation before concrete goes in.

Trees close to the new walls, existing drains and the depth of the original foundations are all checked at the same time. Getting this stage right is what stops cracks between the old house and the new rooms years later.

Planning in the Sevenoaks district

Sevenoaks is the principal town of the Sevenoaks district, 21 miles south-east of Charing Cross, and applications go to Sevenoaks District Council. The district has 41 conservation areas and publishes conservation-area design guidance, so if your house is in one of them that guidance will shape the materials, the roof form and the size of what you can add.

Historic buildings such as Knole House, which dates from 1456, and the almshouses beside Sevenoaks School show how long the town has been built on. Altering a listed building needs listed building consent, and permitted development does not cover it. For other houses, many single storey rear extensions can be built without a full application, while most two storey additions need one. We confirm the route at the site visit.

Who builds it

Our own carpenters and joiners carry out the structural timber, roof, staircase alterations and finishing joinery, and specialist trades we work with regularly handle electrics, plumbing and plastering. The programme is run by one team from groundworks to decoration.

Because the joinery is made in our own Biddenden workshop, details such as a new staircase, internal doors or a fitted run of storage in the extension can be measured on site and built to suit, rather than chosen from a catalogue and adapted. That keeps the new rooms in step with the rest of the house.

The written quote lists what is included so there are no gaps between trades. See our house extensions service, read more about building work in Sevenoaks, or get in touch to arrange a visit.

House extensions in Sevenoaks: questions