You can extend a house in Slough, but more of the area is protected than its reputation would suggest. Hundreds of listed buildings fall within the area. There are more than a dozen conservation areas. The clay underneath moves. For anyone planning a big extension, the paperwork is the main obstacle.
The area counted for this page contains 441 listed buildings. Of those, 17 are Grade I, 26 are Grade II* and 398 are Grade II. Listing covers the whole building, inside and out, so changing windows, removing internal walls or adding a rear extension to one needs listed building consent from the council as well as any planning permission. For the owners of the 398 Grade II buildings, that consent is the main practical hurdle. A buyer looking at a 1950s semi will not need any of this, but anyone buying an old cottage or villa should assume the council will want a say.
The same area includes 14 conservation areas, among them Upton Park and Upton Village, Colnbrook and Burnham. Inside them, demolition needs consent, works to trees need notice, and the council looks harder at anything visible from the street. In Slough, the buildings that conservationists have most regretted losing were the Art Deco factories and post-war offices, and the Twentieth Century Society has complained that many came down with no protection at all. Today the conservation areas protect the villages that came before the factories.
There are 4 scheduled monuments in the area, the strictest tier of protection, including Montem Mound at Salt Hill. They matter mainly to anyone whose land borders one.
Slough's residents alter their homes all the time. The council recorded 8,602 planning applications between April 2024 and July 2026, and 3,506 in the last twelve months. That is a town where builders and scaffolding are a normal sight. Heritage rules have not stopped people extending. They decide which streets need more paperwork.
The ground needs more thought than the paperwork. The British Geological Survey's published shrink-swell hazard reaches class 3 in the area, and about 79% of it is at class 3 or above. That means clay that swells when wet and shrinks when dry, which can move shallow foundations, especially near trees. Before the trading estate arrived, Slough's main businesses were brickfields and farming, and the bricks for Eton College came from them, which shows how much clay lies under the town. An extension here generally needs foundations dug to a depth set by a structural engineer, and building control will expect it.
One listed building in the area is on Historic England's Heritage at Risk register. That marks a building in poor condition, one whose repairs may qualify for grant support and will be watched closely. For the buyer of an ordinary house nearby it changes nothing.
In practice, the answer depends on the house. A modest rear extension or loft conversion on a post-war semi outside a conservation area can often go ahead under permitted development, with no full planning application. Inside a conservation area, or on a listed building, the same work needs consent and those allowances shrink. Check with the council whether the house is listed or inside a conservation area before planning anything ambitious, because that one answer decides how long the process will take.
Freedom to extend is one of Slough's weaker points. Heritage protection is dense, the clay needs proper engineering, and very little on the older streets gets done without the council's involvement.