Do you need planning permission for a house extension in England?
Many house extensions in England do not require a planning application. They fall within Permitted Development (PD) rights — rules set by Parliament that allow certain works without needing formal consent. However, PD rights have specific limits, and not all properties qualify.
Permitted Development rights for extensions (England)
Under Class A of the General Permitted Development Order, you can extend a house without planning permission provided all of the following conditions are met:
Single-storey rear extensions
- Maximum depth: 4 metres from the original rear wall for detached houses
- Maximum depth: 3 metres for semi-detached or terraced houses
- Maximum height: 4 metres (or the eaves height of the original house if lower)
- Must not extend beyond the side wall of the house
- Roof pitch must match the existing house (where within 2 metres of a boundary)
Larger Home Extension Scheme
Under the Larger Home Extension Scheme (Prior Approval), you can build a single-storey rear extension up to 8 metres deep on a detached house, or 6 metres deep on a semi-detached or terraced house, without full planning permission — but you must notify the council and allow neighbours to comment. The council then decides within 42 days.
Two-storey extensions
- Maximum depth: 3 metres from the original rear wall
- Must be at least 7 metres from the rear boundary
- Must not be higher than the existing roof ridge
- Upper-floor windows facing the side boundary must be obscure-glazed and non-opening (unless the opening is more than 1.7m above floor level)
Side extensions
- Single storey only under PD
- Maximum width: half the width of the original house
- Maximum height: 4 metres
The 50% rule: all extensions and outbuildings together must not cover more than 50% of the original garden area. This limit applies to the total built footprint, not just the extension you are planning.
When do you always need planning permission?
Flats and maisonettes
Permitted Development rights do not apply to flats or maisonettes. Any extension to a flat requires a full planning application.
Listed buildings
Listed buildings require Listed Building Consent for any external works, regardless of size. This is in addition to any planning permission that may be required. Unauthorised works to a listed building are a criminal offence.
Conservation areas
Properties in conservation areas have restricted PD rights. Side extensions always need planning permission. Some other restrictions also apply — check with your local planning authority.
Article 4 Directions
Some councils withdraw PD rights in specific areas using an Article 4 Direction. This is common in conservation areas and some housing estates. Your council's planning department can confirm whether this applies to your address.
New build properties
Many new build properties have PD rights removed as a condition of the original planning permission. Check the planning permission documents for your property — usually available on your local council's planning portal.
Does an extension need Building Regulations approval?
Yes — almost always. Building Regulations and planning permission are two completely separate systems. You can have one without the other. Even if your extension falls within PD and needs no planning permission, it still requires Building Regulations approval to ensure it is structurally safe, insulated to current standards, and has adequate drainage, ventilation and fire separation.
Building Regulations are checked by an approved Building Inspector (either from the local council or a private approved inspector). They visit at key stages of construction — foundations, damp proof course, structural steel, roof structure, and at completion.
How to apply for planning permission for an extension
If your extension requires full planning permission:
- Appoint an architect or architectural designer to produce drawings to planning standard
- Submit a householder planning application via the Planning Portal (planningportal.co.uk) — fee is £258 in England (2026)
- Wait 8 weeks for a decision (the statutory determination period)
- If approved, proceed with Building Regulations drawings and appoint a contractor
Certificate of Lawful Development
If your extension falls within PD rights, it is worth applying for a Certificate of Lawful Development (CLD). This is a formal document from the council confirming your extension is lawful under PD. It costs approximately half the planning fee (~£129 in England) and provides proof for future buyers or mortgage lenders. It is not legally required, but it can prevent disputes when you sell.
Frequently asked questions
- How do I know if my house has Permitted Development rights?
- Most houses in England have PD rights unless they are in a conservation area, are listed, are flats, or had PD rights removed when the property was built. The quickest check is to call your local council's planning duty officer — they can confirm over the phone in a few minutes.
- Can my neighbour stop my extension?
- If your extension is within PD limits, neighbours cannot veto it through the planning process — though they can comment under the Larger Home Extension Scheme. If a full planning application is needed, neighbours are consulted, but objections must be material planning considerations (not just personal dislike). If the extension is on or near a shared boundary, the Party Wall Act 1996 also gives neighbours certain rights.
- What is the Party Wall Act and does it apply to extensions?
- The Party Wall etc. Act 1996 applies when you carry out works on or close to a shared boundary or a party wall (a wall shared with a neighbour). For extensions, it is most commonly triggered by excavating for foundations within 3 metres of the neighbour's foundations, or building up to or astride the boundary. You must serve written notice on affected neighbours before work starts. They can consent or appoint a party wall surveyor.
- What happens if I build without planning permission?
- If the extension was within PD limits, there is no issue — but get a Certificate of Lawful Development to document this. If the extension required permission and you built without it, the council can issue an enforcement notice requiring demolition or modification. However, enforcement becomes time-limited after 4 years for extensions (the council cannot enforce after 4 years if the breach is not concealed). Legal advice is recommended if you have an unauthorised extension.