Do I need planning permission for an extension?

Nobody can tell you that from a web page, whoever wrote it. Whether your extension needs permission depends on your property, its planning history, what has already been built on it and what area it sits in, and the only body whose answer counts is your local planning authority.

What this page can usefully do is tell you what the question turns on, so that when you contact the council or a planning consultant you are asking something specific. planning applications are not made here and handling one is not part of the job here.

Some building work can be done without a full planning application, under what are called permitted development rights. It is not a loophole, it is a set of limits, and an extension that stays inside them does not need an application. An extension that exceeds any one of them does.

The limits deal with things like how far a single storey rear extension projects, its height, how close it comes to a boundary, how much of the garden is being built on, and what materials are used. They are different for a detached house and an attached one, and different again for a two storey extension.

Conservation areas. Listed buildings. Properties where an earlier planning permission removed permitted development rights as a condition, which is very common on newer estates and which people frequently do not know about their own house. Flats and maisonettes, which do not have these rights at all.

Also worth knowing: an extension somebody built before you moved in counts against the allowance. Two owners ago somebody may have used up most of it.

This confuses almost everybody. Planning permission is about whether you are allowed to build it. Building regulations are about whether it is built properly: structure, insulation, drainage, fire safety, ventilation. An extension can need no planning permission at all and still absolutely need building regulations approval.

So an extension that does not need permission is not an extension nobody needs to inspect. Getting those two confused is a genuinely expensive mistake and it is worth being clear about which one somebody means when they tell you that you do not need anything.

Your local planning authority is the definitive source, and most councils will answer a general question or offer a pre-application service. The national Planning Portal sets out the permitted development limits in plain terms. For anything complicated, a planning consultant or an architect who works in your area is money well spent before drawings are paid for.

What the quote gives you is a straight view on which parts of what you want look like they need an application, based on having built in the area. That is a starting point for asking, not an answer, and it is not offered as one.