Do I Need Planning Permission for an Extension

Building an extension is one of the most effective ways to increase living space and improve the value of your home. Whether you are planning a rear kitchen extension, an extra bedroom or a new bathroom, extending your property can create a more comfortable and practical layout. Before getting started, however, it is essential to understand whether planning permission is required. The answer depends on the size, location and design of the extension, as well as where your home is situated and what rules apply.

Permitted Development Rights for Extensions

In many cases, homeowners can build extensions without needing formal planning permission by using permitted development rights. These rights allow certain types of building work to be carried out without a planning application, as long as specific limits and conditions are met. To qualify, the extension must be to a house, not a flat or maisonette, and must not be in a conservation area, national park or Area of Outstanding Natural Beauty unless explicitly permitted.

Under permitted development, a single-storey rear extension must not extend more than three metres beyond the original rear wall for a terraced or semi-detached house, or more than four metres for a detached house. Until 2026, larger home extensions of up to six metres for terraced and semi-detached houses and up to eight metres for detached houses may be allowed under the Neighbour Consultation Scheme, but this still requires prior approval from the local authority.

The height of the extension must not exceed four metres for a single-storey build and the eaves must not be higher than the existing house. Two-storey extensions must be no closer than seven metres to the rear boundary and must not extend beyond the side elevation if the extension includes a roof. Materials must match the existing house, and the extension must not take up more than 50 per cent of the land around the original house.

When Planning Permission Is Required

Planning permission is required if your proposed extension does not meet the permitted development criteria. This might include a larger structure, a side extension on certain plots, or the use of materials that differ from the main house. If your home is located in a designated area such as a conservation zone or World Heritage Site, you may also need planning permission for even minor changes.

Extensions that are forward of the principal elevation (the front of the house) will almost always require planning permission. The same applies to properties where permitted development rights have been removed, which is common on newer housing developments or where Article 4 Directions have been imposed by the local authority.

Building Regulations Still Apply

Regardless of whether planning permission is needed, all extensions must comply with Building Regulations. These cover essential aspects such as structural integrity, fire safety, energy efficiency, ventilation, and drainage. You must submit either a building notice or full plans application to your local building control body before work begins. Inspections will be carried out at key stages, and you will receive a completion certificate once the work meets all the required standards.

Planning in Practice

A family in York built a single-storey rear extension measuring three metres from the rear wall and four metres in height. The materials matched the existing house, and the total ground coverage stayed within the permitted 50 per cent limit. This work was completed under permitted development and did not require a planning application, though it was fully approved under Building Regulations. Meanwhile, a homeowner in Brighton extended to the side and rear, with the new build wrapping around the house and including a raised roofline. As the design exceeded height and coverage limits, full planning permission was required. The application succeeded after design adjustments were made to reduce the impact on neighbouring properties.

Designated Areas and Listed Buildings

If you live in a listed building, any extension will require listed building consent in addition to any necessary planning permission. In conservation areas and other protected zones, stricter controls apply to the size, location and appearance of extensions. Local planning authorities may also impose design conditions, such as requiring matching brickwork or roof tiles, to preserve the character of the area.

Neighbour Consultation and Prior Approval

For larger single-storey rear extensions under the Neighbour Consultation Scheme, you must notify your local planning authority before starting work. Your neighbours will be consulted, and if there are no objections, or if objections are overruled, you can proceed. This is not full planning permission, but it is a formal process that ensures your extension is legally compliant.

Certificates and Confirmation

If your extension is covered by permitted development rights, you can apply for a Certificate of Lawful Development. This is not mandatory but offers legal confirmation that your work did not require planning permission. It can be useful if you plan to sell or refinance your home in the future.

Conclusion

In many cases, you do not need planning permission to build an extension in the UK, provided the work complies with permitted development rules. However, if your plans fall outside these limits or your home is in a protected area, a full planning application may be necessary. Regardless of permission status, Building Regulations approval is always required. By understanding the planning system and checking all local requirements in advance, you can extend your home with confidence and peace of mind.