Yes, but you will be asking permission more often than you would in most of south London. Plenty of the area falls inside a conservation area. The district also has dozens of listed buildings. The clay underneath has its own say on foundations. People still extend here, and they do it by filling in forms.
Historic England lists 57 buildings in and around Upper Norwood. One is Grade I, three are Grade II* and the other 53 are Grade II. Listing covers the inside of a building as well as the outside, so in a listed house even a new partition wall or a different window needs listed building consent before anyone picks up a drill. Most homes here are not listed, but if yours is, nearly any change has to be argued for in writing.
Conservation areas cover far more ground. Twelve of them reach into the area, among them Beulah Hill, Church Road, Harold Road, Gipsy Hill, Elderwood and Crystal Palace Park. Inside them the council looks harder at anything visible from the street, including roofs, frontages, front gardens and the materials an extension is built from. Upper Norwood is also split between four boroughs, Croydon, Lambeth, Southwark and Bromley, and each runs its own planning department. Find out which council and which conservation area a house falls under while you are still only looking at it, because the same rear extension can be a short application on one side of a boundary and a long correspondence on the other.
Plenty of people go through the process anyway. Between April 2024 and June 2026, 714 planning applications were made across the area, 299 of them in the last twelve months. That is a district where people keep trying to change their homes, and keep doing it on paper.
The ground is a separate issue. The British Geological Survey puts the whole area at class 3 for shrink-swell, which means clay that swells when wet and shrinks in dry summers. That does not stop anyone building, but it does decide how. An extension on this ground generally needs deeper foundations than one on firmer soil, and a structural engineer should look at the plans before the builder quotes for them. Trees near the house make the clay's behaviour harder to predict.
Seven listed buildings in the area are on Historic England's Heritage at Risk register. That means they are in poor enough repair to be flagged, and work on them may attract grant support and will certainly attract close attention. None of it affects the owner of an ordinary house down the road, except as a reminder of how closely the council watches old buildings here.
In practice, a house outside the conservation areas and off the listed register gets the normal freedoms, and some smaller extensions may need no application at all. Within the twelve conservation areas, assume more of the work needs consent. Most homes in the area are flats, and changing a flat means dealing with the freeholder as well as the council. On a hill where nineteenth-century villas stand next to post-war blocks, the planning answer can change from one front door to the next.
Extending in Upper Norwood is possible, but it is a slower and more formal process than in most of south London. Buyers who want to add rooms without paperwork will find it easier somewhere less historic.