Yes, for most houses, with the clay underneath and the neighbours next door as the bigger obstacles. Hardly any homes are listed. One estate is a conservation area. The neighbours file planning applications all year round. The heritage rules are light; the ground and the paperwork are where the effort goes.
Wallington and its surroundings hold 81 listed buildings: 1 at grade I, 3 at grade II* and 77 at grade II. Listing covers the whole building, inside and out, so almost any alteration to one needs listed building consent from the London Borough of Sutton on top of ordinary planning permission. Eighty-one buildings is a thin spread across a town made mostly of semis, terraces and flats, so the chance that the house in question is one of them is small, and the list entry will tell you in a minute if it is.
There is one conservation area, The Webb Estate. Inside it the council can require consent for work that would pass without a second look elsewhere, from extensions to changes on the front of the house and to trees, and it judges any proposal on how it fits the character of the estate. Check whether the address falls inside the boundary on the council's conservation area map; the same rear extension can be routine on one road and a planning application on the next.
Three scheduled monuments lie in and around the area, the strictest tier of heritage protection, which matters only for land next to one.
The neighbours are busy. The council received 676 planning applications across Wallington between April 2024 and June 2026, 275 of them in the twelve months to June 2026. That is a town adding space to the houses it already has, one application at a time.
The ground needs more thought than the heritage. The British Geological Survey rates shrink-swell clay in Wallington at up to class 3 on its scale, and about 69% of postcodes reach that class. Clay of this kind swells when wet and shrinks when dry, so extensions here often need deeper foundations than on firmer ground, and building control will expect them to be designed for it. Get a structural engineer's view on the foundations early, especially near large trees. The trees that make the gardens worth having are the ones the engineer will ask about first.
Five listed buildings in the area appear on Historic England's Heritage at Risk register, which records historic buildings in poor condition. Their repair may attract grant support and will certainly attract scrutiny, but that concerns their owners, not the buyer of an ordinary house down the road.
For a house outside the listed buildings and The Webb Estate, the national permitted development rules allow many single-storey rear extensions and some loft conversions without a full planning application, within size limits. Flats are different: they carry no householder permitted development rights at all, so any extension needs planning permission, and with about 42% of Wallington's homes being flats that applies to a large slice of the market. Prior approval and building regulations apply either way.
Wallington is middling for anyone wanting to extend: the heritage controls barely register for most houses, while the clay and the busy planning register make every project a little more work than it looks on the drawing.