You can, but more slowly than buyers expect. The area has dozens of listed buildings. Conservation areas cover streets all over the town. The clay underneath moves with the weather. The neighbours still lodge hundreds of applications a year. Surbiton does get extended, but only with the right forms and the right foundations.
There are 57 listed buildings in the area. None is Grade I, two are Grade II* and 55 are Grade II. Listing covers the whole building, inside and out, so changes that affect its character need listed building consent as well as any planning permission, and carrying out work without consent is a criminal offence. For most Surbiton homes that won't apply. For the owners of those 57, the rules are strict.
Sixteen conservation areas lie in and around Surbiton, including Grove Crescent, Fairfield and Knights Park, Claremont Road and Cadogan Road. Inside them the council looks harder at anything visible from the street, and some works a house owner could do freely elsewhere need an application. Two neighbouring streets can follow very different rules, one where a loft conversion is routine and one where the council takes an interest in the window frames.
The council received 1,152 planning applications for the area between April 2024 and July 2026, and 379 in the most recent twelve months. That doesn't say how many were approved, but it does show that Surbiton homes are altered all the time, form by form. The council's online register lists every application for a given street, and the recent extensions on the street you're looking at are the best evidence of what it will allow there.
The British Geological Survey puts every postcode in Surbiton, 100% of them, in shrink-swell class 3. Clay at that class swells when it's wet and shrinks when it dries, and nearby trees make the movement worse. For an extension, that usually means deeper foundations and a structural engineer looking at the soil and the trees before the drawings are final. That's a building-cost question, not a reason to panic, and the engineer's fee is small next to a cracked rear wall.
Two listed buildings in the area are on Historic England's Heritage at Risk register. That means buildings in poor repair, whose restoration may attract grant money and will certainly attract close attention. For the owner of an ordinary house down the road they change nothing, though they do show how seriously the old buildings here are watched.
Permitted development lets many houses add a modest rear extension or a loft conversion without full planning permission. Listing, conservation-area status and the council's own restrictions can all reduce or remove those rights, and flats don't have the householder rights at all. With more than half of Surbiton's homes being flats, a lot of buyers here will need full permission for anything beyond redecorating. Ask the council what rights the specific property still has before assuming a plan will go ahead.
Freedom to extend is one of Surbiton's weaker points. It can be done, but heritage protection, conservation areas and moving clay mean every project starts with paperwork and an engineer.