Planning Permission for Extensions: What You Need to Know

What is Permitted Development?

Permitted Development (PD) rights allow certain building works without full planning permission. For house extensions, PD rights cover single storey rear extensions up to 4m deep for detached houses (3m for others), and up to 6m/8m with prior approval under the Larger Home Extension Scheme.

Side extensions fall under PD if they're single storey, less than half the width of the original house, and don't extend beyond the front elevation. Double storey side extensions generally require planning permission.

When Do You Need Planning Permission?

You need planning permission if: your extension exceeds PD limits, your property is in a conservation area with restricted PD rights, your property is listed, an Article 4 direction removes PD rights, or you want a double storey side extension.

London boroughs vary in their approach. Islington, Camden, and Westminster have extensive conservation areas. Always check with your local planning authority before assuming PD rights apply.

How Does the Planning Application Process Work?

The planning process involves preparing drawings and design statements, submitting the application online via Planning Portal (the householder fee is set nationally and listed on gov.uk), waiting 8 to 13 weeks for determination, and potentially addressing conditions if approved.

We can coordinate planning applications for our clients as an optional service, working with architects to prepare compliant submissions. We also manage neighbour consultations and planning officer discussions.

What Changes in Conservation Areas and Listed Buildings?

Conservation areas have stricter controls. Many London boroughs have Article 4 directions removing certain PD rights. Extensions must preserve or enhance the area's character.

Listed buildings require Listed Building Consent for any works affecting character. This is separate from planning permission and has no fee, but carries criminal penalties for non compliance.

What Is a Lawful Development Certificate?

Even when using PD rights, we recommend applying for a Lawful Development Certificate (LDC). An LDC costs £103 and provides legal confirmation that your extension is lawful. This is valuable when selling the property.

Without an LDC, buyers' solicitors may question whether the extension complies with planning rules, potentially delaying or jeopardising sales.

What Is the Larger Home Extension Scheme?

Under permitted development, a single storey rear extension on a semi-detached or terraced house can normally extend up to 3 metres, and up to 4 metres for a detached house. Under the larger home extension scheme these limits can be doubled, to 6 metres and 8 metres, but only if you notify your local planning authority and your adjoining neighbours are consulted. If a neighbour objects, the council must decide whether the impact on that neighbour is acceptable before you can build.

This scheme does not apply in every location, and it does not apply to flats or maisonettes. Always check with the council or apply for a Lawful Development Certificate before starting.

Planning Permission and Building Regulations Are Separate

Even where an extension does not need planning permission, it will almost always need Building Regulations approval. Planning looks at how the extension affects the area and neighbours. Building Regulations cover structure, fire safety, insulation, drainage and ventilation. You need to deal with both, and the work will be inspected by Building Control at set stages.

Planning permission and Building Regulations approval are separate applications, made to different parts of the council or to an approved inspector, with separate decisions and separate fees.

What Is an Article 4 Direction?

Some councils have removed permitted development rights in particular streets or areas through an Article 4 Direction, often to protect the character of a conservation area. In those areas, work that would normally be permitted development, such as changing windows or painting the front of a house, may need a full planning application. The council's planning pages list where Article 4 Directions apply, and our local area pages link to the relevant council.

Sources and Further Reading

Planning Portal, planning permission for extensions: https://www.planningportal.co.uk/permission/common-projects/extensions/planning-permission

Planning application fees: https://www.gov.uk/guidance/fees-for-planning-applications

Party walls: https://www.gov.uk/party-wall-etc-act-1996-guidance