Yes, and Swanley makes it easier than most. Fourteen buildings are listed, all at the lowest grade. No conservation areas cover the town. Hundreds of planning applications go in every year. The ground is the catch, with shrink-swell clay under almost all of it. Light on paperwork, heavy on clay.
Historic England lists 14 buildings in the area, and every one of them is Grade II, with none at Grade I and none at Grade II*. Listing covers the whole building, inside and out, so any change that affects its character needs listed building consent on top of any planning permission, and doing the work without it is a criminal offence. With only 14 to dodge, the odds of buying one by accident are low, and the conveyancing searches will say so either way. Swanley was mostly built between the war and the late 1980s, and the town has very little that anyone thought to protect, plus fourteen buildings that somebody did.
The neighbours are busy. Planning records show 692 applications in the area between April 2024 and June 2026, with 306 of them in the most recent twelve months. That is a town where people alter their homes routinely, and where a scaffold on the street is a normal sight. Loft conversions and side extensions are how a post-war semi gets its fourth bedroom without the owners moving to get one.
The British Geological Survey's shrink-swell hazard reaches class 3 in the area, and about 93% of postcodes are at class 3 or higher. Clay soils swell when wet and shrink when dry, and the movement can crack foundations that are too shallow for the ground they sit on, especially near thirsty trees. For an extension that usually means deeper foundations than the builder's first quote assumed, and a structural engineer's view before the design is settled. Some gardens still have apple and pear trees from the town's orchard days, and a mature fruit tree beside a proposed footing is exactly the kind of thing an engineer will want to see.
Because the town has no conservation areas and very few listed buildings, most ordinary houses keep their full permitted development rights, which means many single-storey rear extensions, loft conversions and outbuildings can go ahead without a full planning application, within the national size limits. Larger or two-storey work needs planning permission from Sevenoaks District Council in the usual way. Hockenden is the exception on paper, because it falls in the London Borough of Bromley, so its planning goes to a different council. For anything near the limits, a lawful development certificate from the right council settles whether the work counts as permitted development, which is far cheaper than finding out from an enforcement letter.
Swanley gives homeowners more freedom to extend than most places, held back mainly by the clay underneath and by a short list of listed buildings that few buyers will ever own.