Usually, yes. Most of Sunbury's housing is post-war, and those streets have no special protection. Listed buildings are relatively few. The river frontage is mostly covered by conservation areas. The protection is concentrated where the old houses are, and the newer streets have much more freedom.
Historic England lists 66 buildings in and around Sunbury. None is Grade I, 4 are Grade II* and 62 are Grade II. Owning one means you need listed building consent for most changes, inside and out, alongside ordinary planning permission. Altering a listed building without consent is a criminal offence. Sixty-six listed buildings is a small number in a town where only about one home in eight was built before 1930, so most buyers will never own one.
There are five conservation areas in the area: Lower Sunbury, Lower Halliford, Upper Halliford, Hanworth Road and Walton Riverside. Inside them, the council looks harder at anything visible from the street, including windows, front boundaries, roof lines and side extensions. Demolition needs consent, and some changes that are normally permitted have to go through the council. Check on Spelthorne's conservation-area map which side of the boundary the house is on. On the older streets near the river, the line can split a single road.
There are also two scheduled monuments in the area, the strictest level of protection. Scheduled monument consent comes from the national government, not the council. They only matter if your land is next to one.
People in Sunbury apply for planning permission all the time. Between April 2024 and July 2026, 2,732 planning applications were recorded across the area, 1,090 of them in the last twelve months. Those include extensions, loft conversions, trees, outbuildings and new windows. The figures only show how many applications were made. They say nothing about how many were approved.
In practice, a post-war semi or detached house outside the conservation areas can usually take a modest rear extension or a loft conversion under national permitted development rights, within size limits. A prior-approval or lawful development certificate from the council confirms that before the builders start. Flats don't have those rights, and any property inside a conservation area or near the river needs more paperwork. Sir Christopher Wren once drew up plans for an army barracks on the western part of Sunbury's manor, and they were never built. If your dormer gets turned down, you're in good company.
Sunbury is a middling place to extend. The post-war streets give you plenty of freedom, while the riverside conservation areas will scrutinise every window.