Do I need planning permission for a house extension in Cambridge?

Many houses in England have permitted development rights, which allow certain extensions without the need for a planning application, provided specific limits and conditions are met. For a single-storey rear extension, the usual maximum depth is 3 metres from the original rear wall for terraced and semi-detached houses, or 4 metres for detached houses. In some circumstances, larger extensions may be possible through the prior approval process, although additional restrictions apply.

Permitted development can be an entirely appropriate route, but working within its limits does not necessarily lead to the best design. The restrictions can influence the scale, position and form of an extension, sometimes limiting what can be achieved in terms of layout, natural light and the relationship between spaces.

A full planning application can offer greater design freedom, allowing us to consider the house and site as a whole rather than designing around predetermined limits. This can open up opportunities for a more considered layout, more effective use of the available land and budget, and a more coherent architectural response to the existing building. We consider both routes from the outset, advising on the approach that offers the best outcome for each project.

You will normally need planning permission if the extension goes beyond the permitted development limits, if it is two storeys at the side or close to a boundary, or if the property is a flat or maisonette, which has no permitted development rights for extensions.

Permitted development can also be removed or restricted for an individual property by an earlier planning condition, or across an area by an Article 4 direction. It is always worth checking the planning history before assuming an extension is permitted development.

Much of Cambridge lies within conservation areas, where permitted development rights are tighter. Side extensions, for example, are not permitted development in a conservation area, and neither is cladding the outside of the house, so many extensions that would be straightforward elsewhere need a planning application.

If the house is listed, listed building consent is needed for almost any extension or alteration that affects its character, whatever the size – permitted development does not override this. Our guide to listed building consent explains what that involves.

If you believe an extension is permitted development, you can apply to the council for a Lawful Development Certificate. It isn’t compulsory, but it gives formal confirmation – useful peace of mind, and helpful when you come to sell.

Where planning permission is needed, a clear, well-reasoned application makes a real difference. We prepare drawings, design and access statements and, where required, heritage statements – and we have a 100% planning approval record to date.