Do I Need Planning Permission for my house extension/outbuilding?

Your Starting Point: Permission vs. Permitted Development

This guide breaks down the essential rules for homeowners in the UK looking to extend their property or add an outbuilding. Understanding your rights is the first and most important step.

Quick Checklist

• Many smaller extensions and outbuildings fall under Permitted Development (PD) rights, meaning no formal planning application is needed.

• These rights come with strict rules on size, height, location, and materials.

• Rights can be removed by your local council (e.g., in Conservation Areas) or by past planning conditions. Always check first.

• If your project exceeds PD limits, you will need to apply for full planning permission.

What Are Permitted Development Rights?

Think of Permitted Development (PD) rights as a pre-approved grant of planning permission from Parliament. The government has decided that certain types of minor home improvements do not need to go through the full scrutiny of a planning application, provided they meet a strict set of criteria. The key legal document for England is The Town and Country Planning (General Permitted Development) (England) Order 2015, often referred to as the GPDO. If your project fits perfectly within these rules, you can build without a formal application. If it doesn't, you must apply for planning permission.

Rules for House Extensions (England)

Building an extension is the most common project homeowners undertake. Under permitted development, the main limitations depend on the type of house and the extension's size and location.

*Note: Rear extensions over 4m (detached) or 3m (other) require the "Prior Approval" process, where the council consults your neighbours.

Materials used for any exterior work must be of a similar appearance to those on the existing house.

Rules for Outbuildings (England)

This category includes sheds, garages, garden rooms, and home offices. The key rule for an outbuilding is that its use must be 'incidental to the enjoyment of the dwellinghouse'. It cannot be used as self-contained living accommodation.

Key rules for outbuildings:

• Location: Cannot be built forward of the principal elevation (the front) of the original house.

• Height: Maximum eaves height of 2.5m. Maximum overall height of 4m for a dual-pitched roof or 3m for any other roof type. If the building is within 2m of a boundary, the overall height is limited to 2.5m.

• Coverage: Outbuildings and other additions must not cover more than 50% of the total area of land around the original house.

The Crucial Checks Before You Build

Even if your project seems to fit the rules above, you must check for local constraints that can override your Permitted Development rights. This is the step many homeowners miss.

1. Article 4 Directions: A local council can issue an Article 4 Direction to remove specific PD rights in an area. This is common in Conservation Areas where the council wants to preserve the architectural character. Search for "Article 4 Direction" on your local council's website.

2. Designated Land: Your PD rights are more restricted if you live in a Conservation Area, a National Park, an Area of Outstanding Natural Beauty (AONB), or a World Heritage Site. For example, you cannot build a side extension or an outbuilding between the side of your house and the boundary on designated land.

3. Listed Buildings: If you live in a listed building, you will need Listed Building Consent for most works, and PD rights are severely restricted. Do not assume you can build anything without consent.

4. Previous Planning Conditions: Check the planning history of your property. A condition on a previous planning permission may have removed future Permitted Development rights.

5. Flats and Maisonettes: These property types do not have the same householder PD rights. You will almost certainly need to apply for full planning permission.

The Smart Move: Get a Certificate of Lawfulness

If you are confident your project is a permitted development, it is wise to apply for a Certificate of Lawfulness of Proposed Use or Development (CLOPUD). This is not a planning application, but an application to the council to confirm that your proposal is lawful. It provides legal certainty and is invaluable when you come to sell your property.

What About Scotland, Wales, and Northern Ireland?

While the principles are similar, the specific size limits and conditions for permitted development differ in the devolved nations. Always check the official guidance for your location:

• Scotland: mygov.scot

• Wales: gov.wales

• Northern Ireland: planningni.gov.uk