West Northamptonshire Council is the local planning authority. It is a unitary council, so planning, building control and the roads all sit with the same authority.
Twenty conservation areas
Northampton has twenty of them, and the Boot and Shoe Quarter is the one most likely to affect a house we are asked to work on. Inside a conservation area the permitted development limits reduce and side extensions lose their permitted development rights entirely. In the Boot and Shoe Quarter the council is also concerned with the industrial fabric, not only the housing, so alterations to a former works or to a rear workshop building get looked at differently from the same work on an ordinary terrace.
The Article 4 direction, and what it is not
Northampton has a borough wide Article 4 direction, and it is worth being precise about it because it causes a great deal of unnecessary worry. It covers the creation of new houses in multiple occupation. If you intend to convert a family house into shared accommodation, that needs planning permission here rather than being automatic, anywhere in the borough. If you are extending or altering your own home to live in, this direction does not apply to you at all.
Everything else
On the interwar, post-war and modern housing across the town the ordinary rules apply, and a single storey rear extension often falls within permitted development. Permitted development is not an exemption from Building Regulations, and a full plans application is still required. We do not make that application, but we arrange and meet the inspections that follow it and we see the work through to sign off.