Do I Need Planning Permission for a Home Extension?

Short answer: many single-storey rear extensions can be built under permitted development, without a full planning application, provided they meet size, height and boundary limits. Larger extensions, side extensions facing a highway, extensions on designated land, and properties where permitted development rights have been removed by a planning condition, usually need full planning permission.

What is permitted development?

Permitted development rights are a national grant of planning permission that let homeowners carry out certain types of work without submitting a full application, provided the work stays within defined limits on size, height, position and materials. They apply to houses, not flats or maisonettes, and can be removed or restricted by an "Article 4 direction" or a condition on an existing planning permission.

What typically pushes a project into full planning permission?

• Extensions beyond the depth, height or volume limits set for permitted development
• Extensions to the side of the house facing a road, above certain size limits
• Work on designated land, including conservation areas, National Parks and National Landscapes (formerly AONBs)
• Listed buildings, where listed building consent is also usually required for internal and external alterations
• Properties where an Article 4 direction removes permitted development rights, common in some conservation areas
• Flats and maisonettes, which do not benefit from the same permitted development rights as houses

How we approach this on your project

We check your property's planning history, its designation status (conservation area, listed status, Article 4 directions) and the proposed extension's dimensions against current permitted development limits during the feasibility stage, before you commit to a design. Where a full application is likely to be needed, we factor realistic timescales for a decision into your project programme.

What if I build without the right permission?

Work carried out without the required planning permission can be subject to enforcement action by the local authority, and can cause complications when selling the property later. Where there is any doubt, we recommend either a full application or a Lawful Development Certificate confirming permitted development status in writing.

Planning and Building Regulations rules are set nationally but applied locally, and they change from time to time. This article reflects general guidance correct at the time of publication — always confirm the current position for your specific property with your local planning authority or at gov.uk and the Planning Portal before relying on it.