Many house extensions in Dorset can be built without a full planning application, but the answer depends on the size of the extension, the type of house and exactly where you live. A modest rear extension in Poole and the same design in a Purbeck village can be treated very differently. Here is how to work out which side of the line your project falls on.
Most houses have permitted development rights, which allow certain extensions without applying for planning permission. If your design stays inside the limits, you can go straight to detailed drawings and building regulations.
The main limits for a typical house are:
You will need householder planning permission if the extension goes beyond those limits, sits forward of the front of the house, or includes a balcony, veranda or raised platform. Wraparound extensions that join a side and rear extension usually need permission too.
Flats and maisonettes have no permitted development rights for extensions, so any extension needs an application. The same can apply to newer homes. Many estates built in the last 20 to 30 years around Poole, Wimborne and Dorchester had their rights removed as a condition of the original planning approval, so check before you assume.
There is a middle route for larger single-storey rear extensions: up to 6 metres on an attached house or 8 metres on a detached one. This uses a prior approval process in which the council consults your neighbours and normally decides within 42 days. It is not available in conservation areas or protected landscapes.
A large part of the county is protected landscape. The Dorset National Landscape covers roughly 40 per cent of the county, including much of Purbeck and the west, and Cranborne Chase covers a further area in the north east. Add well over a hundred conservation areas, from Poole Old Town and Branksome Park to villages such as Corfe Castle and Cerne Abbas, and a lot of homes fall under tighter rules.
In these areas, side extensions and two-storey rear extensions need planning permission, as does cladding the outside of the house. Some streets also have Article 4 directions that remove further rights. If your home is listed, you need listed building consent for almost any extension, whatever its size.
Which council you deal with depends on your address. Bournemouth, Christchurch and Poole are covered by BCP Council. The rest of the county comes under Dorset Council. Both have online maps showing conservation areas and other designations.
A householder application currently costs a little over £500 in council fees, plus the cost of drawings. Both local councils aim to decide within 8 weeks, though 10 to 12 weeks is not unusual at busy times or where a design needs amending.
If you believe your extension is permitted development, consider applying for a lawful development certificate. It costs about half the planning fee and gives you written confirmation from the council, which solicitors often ask for when you sell.
Planning is only one approval. Almost every extension also needs building regulations sign-off covering structure, insulation, drainage and fire safety. If you are building on or close to a shared boundary, you may also need to serve a party wall notice on your neighbour.
Under permitted development, a single-storey rear extension can usually project 3 metres on a semi-detached or terraced house and 4 metres on a detached house. Larger extensions of up to 6 or 8 metres may be possible through prior approval, but not in conservation areas or protected landscapes.
BCP Council and Dorset Council both aim to decide householder applications within 8 weeks of validation. Allow 10 to 12 weeks in practice, plus time beforehand to prepare drawings.
Yes, in almost all cases. Building regulations are separate from planning and apply to nearly every extension, regardless of whether it counts as permitted development.
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