Yes, you might need planning permission for an extension, as it depends on the size, height, and location of your proposed build, as well as the type of property and its surroundings. Many smaller extensions can be built under "permitted development" rights, meaning you won't need full planning permission, but there are crucial limits to these rights.
Understanding Permitted Development Rights
Permitted development rights allow homeowners to make certain changes to their property without needing to apply for planning permission. These rights are set out by the government and are subject to specific conditions and limitations designed to control development and protect local amenities.
However, it's vital to understand that not all extensions qualify, and breaching these limits will require a full planning application.
When Planning Permission is Definitely Required
You will need to apply for planning permission for your extension in several key circumstances, including:
- Height Restrictions:
- Any part of the works are higher than the highest part of the roof of the existing house. This is a critical point; even a small section of your extension exceeding the existing roof's highest point will trigger the need for planning permission.
- The height of the eaves of the extension would be higher than the eaves of the existing house. If the new extension's eaves are taller than those of your original home, you'll need permission.
- Exceeding Size Limits:
- Single-storey rear extensions that extend beyond the rear wall of the original house by more than 4 metres for a detached house, or 3 metres for a semi-detached or terraced house. (Note: larger single-storey rear extensions up to 8m for detached, and 6m for others, can be built under a Neighbour Consultation Scheme, but this is a separate process).
- Two-storey extensions that extend beyond the rear wall of the original house by more than 3 metres.
- Total footprint: If the extension, along with any previous extensions, covers more than half the area of land around the "original house." The "original house" is defined as it was on 1 July 1948 or when it was built if after that date.
- Specific Locations & Property Types:
- Fronting a highway: An extension that extends beyond the principal elevation or side elevation fronting a highway (e.g., a road or public footpath).
- Designated Land: Properties in designated areas such as:
- Conservation Areas
- Areas of Outstanding Natural Beauty (AONB)
- National Parks
- The Broads
- World Heritage Sites
- Extensions on designated land typically have more restricted permitted development rights.
- Flats, maisonettes, or some other types of property generally do not have permitted development rights for extensions.
- Listed Buildings always require Listed Building Consent, in addition to planning permission if applicable.
Key Permitted Development Conditions for Extensions
To help you quickly assess whether your extension might fall under permitted development, here's a summary of common conditions:
| Aspect | Permitted Development Condition (General) |
|---|---|
| Max. Height | Single-storey: 4 metres (overall). Two-storey: 3 metres from ground level to eaves (for side/rear), or existing eaves height if lower. Crucially, no part higher than existing roof's highest part. |
| Eaves Height | For single-storey, max 3 metres if within 2 metres of a boundary. Cannot be higher than the eaves of the existing house. |
| Rear Extension Size | Detached: Max 4m (single-storey). Semi/Terraced: Max 3m (single-storey). (Excludes Neighbour Consultation Scheme which allows up to 8m/6m). Two-storey: Max 3m from rear wall. |
| Side Extension Size | Must be single-storey, max 4m high (or 3m if within 2m of boundary). Width must not exceed half the width of the original house. |
| Total Footprint | Extensions (and other buildings) must not cover more than 50% of the original garden area. |
| Materials | Materials used for the exterior of any extension should be similar in appearance to those of the existing house. |
| Fronting Highway | No extension forward of the principal elevation or side elevation fronting a highway. |
Please note: This table provides general guidance. Specific rules can vary, and it's always essential to check the official guidance.
Practical Steps to Take
- Check the Planning Portal: The Planning Portal is the official government website for planning and building regulations in England. It offers interactive guides and detailed explanations of permitted development rights.
- Consult Your Local Planning Authority (LPA): Even if you believe your extension falls under permitted development, it's highly recommended to apply for a "Lawful Development Certificate" from your local council. This is a formal document that proves your extension is legal and won't be subject to enforcement action later, which can be crucial when selling your property.
- Consider Building Regulations: Planning permission and building regulations are separate. Even if your extension doesn't need planning permission, it will almost certainly need to comply with Building Regulations, which cover health, safety, welfare, and environmental performance.
- Party Wall Act: If your extension is near a boundary with a neighbour, you might need to comply with the Party Wall Act 1996, which requires you to notify neighbours of your proposed work.
In conclusion, while many extensions can proceed without full planning permission under permitted development rights, careful assessment against specific criteria, especially regarding height and size, is essential. When in doubt, always consult your local planning authority.
