Yes, for most homes in New Southgate, because none of it is in a conservation area. A few dozen buildings are listed. Neighbours put in planning applications all the time. The clay under the houses is the part to take seriously. The planning rules are lighter than the foundations will need to be.
Historic England lists 73 buildings within the area's bounding box. One is Grade I, 11 are Grade II* and 61 are Grade II. Listing means the building's character is protected inside and out, so almost any change to one needs listed building consent on top of any planning permission, and work done without it can be an offence. Seventy-three buildings is a small number among nearly 20,000 homes on the council tax list. Few buyers here will end up owning one, though some will live next door to one, and that can affect what is allowed on the neighbouring plot. With no conservation area anywhere, the ordinary semi or terrace has no special heritage controls.
Planning records for the area show 807 applications between April 2024 and June 2026, 282 of them in the last twelve months. That is plenty of evidence that people here extend, convert and alter their homes. The hamlet of Colney Hatch was once known for how tightly its development was held back, but its streets have been making up for it since.
The British Geological Survey puts the area in shrink-swell class 3, and every postcode reaches it. That is a published hazard class for clay ground, which swells when wet and shrinks when dry, and it bears on any extension. Foundations may need to go deeper than a builder would usually dig, and trees close to the new wall matter more than they would elsewhere. Get a structural engineer's view at the design stage. This is a common condition for building in this part of London, and it is something to plan for. The engineer, the builder and the building control officer will all expect it.
Three listed buildings in the area are on Historic England's Heritage at Risk register. These are buildings in poor condition, and their repair may qualify for grant support and will be closely scrutinised. For anyone buying an ordinary house nearby, they are part of the local history, and they don't create any obligation for the neighbours.
In practice, a house owner here starts with the national permitted development rights, which allow some rear extensions, loft conversions and outbuildings without a full planning application, subject to their size limits. Flats are a different matter. Almost half the homes here are flats, and their owners need planning permission for most external changes and usually the freeholder's consent as well. New Southgate straddles Barnet, Enfield and a corner of Haringey, so the first thing to find out is which council covers the address, and then ask that council whether any Article 4 direction removes permitted development rights on the street.
New Southgate leaves owners a middling amount of freedom to extend. Heritage rules affect very few homes, and the clay ground is the main thing an owner has to plan around.