You can extend a house in Lewisham, but the old buildings and the ground underneath both get a say. Hundreds of listed buildings sit in and around the town. There is a conservation area to steer round. The soil moves with the weather across the whole area. Most homes are flats, which shrinks the question before planning even starts.
Historic England records 229 listed buildings within the area's boundary box, 2 at Grade I, 14 at Grade II* and 213 at Grade II. Listing covers the whole building, inside and out, so changing a listed home means listed building consent on top of any planning permission, and the council will want to know about windows, roofs, joinery and anything structural. With 213 at Grade II, the ordinary listed house here is the commonest case, and the rules are the same for a modest terrace as for a church.
One conservation area falls within the same boundary box. Inside a conservation area the council takes a closer interest in demolition, frontages, roofs and anything visible from the street, and it can bring extra consents that a house a few roads away would not need. Lewisham council can confirm whether a given address is inside the boundary and what additional controls apply there, and that is worth asking at the very start, because the answer can differ between neighbouring streets.
The area also holds one scheduled monument, the strictest tier of heritage protection, which matters mainly to anyone whose land sits next to it.
Lewisham council's planning register records 1,082 applications in the area between April 2024 and June 2026, and 480 of them in the last twelve months. People here extend, convert and alter their homes all the time. Whatever the council's appetite for kitchen extensions, the neighbours test it 480 times a year.
The British Geological Survey rates shrink-swell ground at class 3 across the whole area, which means the soil swells when wet and shrinks when dry enough to move foundations if they are not designed for it. For an extension, that means a structural engineer's view, deeper foundations than a builder might quote by habit, and some thought about nearby trees, whose roots dry the ground out in summer. Every postcode here shares the same class, so it is a design question for every project and no reason to avoid any particular street.
Nine listed buildings in the area are on Historic England's Heritage at Risk register. That marks buildings in poor condition whose repair may attract grant support and will certainly attract scrutiny. For someone buying an ordinary house nearby it changes nothing, and for someone buying one of the nine it changes almost everything.
For a house outside the conservation area and off the listed register, many smaller extensions can go ahead under permitted development without a full application, though the limits are tight and the council has the final word on whether a project fits them. Flats are a different matter. Most external changes to a flat need planning permission, and a leaseholder will usually need the freeholder's consent as well, which in a town where most homes are flats makes the freeholder the first planning authority many buyers meet.
Freedom to extend here is fairly limited. An unlisted house outside the conservation area can grow with some care for the ground, while a listed house or a flat comes with more paperwork than floor space.