Guides · 5 min
Basements
A basement is a big project. Planning and the party wall are separate problems.
When planning comes into it
Digging out under the existing house, with no extra light wells at the front, is sometimes treated as not needing planning permission. The moment you add a light well at the front, raise the garden, or extend the basement past the house, you should assume an application.
Some boroughs, especially in inner London, have clear local rules on basements because of neighbours, trees and flooding. Kensington and Chelsea is a well-known example. Do not copy that rule onto a suburban borough.
The other permissions
Building regulations apply. If you dig near a neighbour, the Party Wall Act usually applies too. A structural engineer is not optional.
A basement is rarely the cheap way to add a room. Get a range of quotes before you offer a price that depends on it.
Check with your council. Rules change, and every house is different.
Questions
Is a basement permitted development?
Sometimes, if it stays under the house and does not change the outside. Light wells and front gardens often need permission.
Will my neighbour have a say?
Under the Party Wall Act, yes, if you excavate near them. That is separate from planning.
Check with your council. Rules change, and every house is different.