North 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, which keeps the practical side simpler than it is in the two-tier districts.
The town is largely undesignated, and that matters
Because the residential town was built from 1954 onward, the great majority of Corby housing is not in a conservation area and is not listed. In practice that makes this one of the more straightforward places on our patch to get an extension through, and it is worth saying plainly rather than implying constraints that do not exist. A single storey rear extension of up to four metres on a detached house or three on a semi frequently falls within permitted development, and the generous plots mean there is often room to use the full allowance.
There is also the larger home extension route, allowing up to eight metres on a detached house or six on any other by prior approval rather than full permission, with neighbours notified and an answer in about six weeks. On Corby plot sizes that route is more often genuinely usable than it is elsewhere.
Where it does get complicated
The surrounding stone villages are designated, and there the ordinary conservation area rules apply: reduced permitted development limits and no permitted development rights for a side extension. Estate covenants also turn up more often on the newer developments than people expect, and a covenant is a private legal matter rather than a planning one, so planning permission does not override it.
Building Regulations
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.