Good news: many house extensions in London do not need full planning permission. They can be built under what are called permitted development rights. This guide explains the main limits, when you do need permission, and the other approvals that still apply.
What Are Permitted Development Rights?
Permitted development (PD) rights are national rules that allow homeowners to extend their house up to certain sizes without a full planning application. They apply to houses – flats and maisonettes generally do not have these rights.
Single-Storey Rear Extensions: The Limits
- Beyond the rear wall of the original house: up to 3 metres for attached houses, or 4 metres for a detached house, under standard rights.
- Under the larger home extension scheme (with prior approval from the council): up to 6 metres for attached houses, or 8 metres for a detached house.
- Maximum height of 4 metres for a single-storey extension.
- If the extension is within 2 metres of a boundary, the eaves height must be no more than 3 metres.
- Materials should be similar in appearance to the existing house.
Side and Two-Storey Extensions
Side extensions under PD must be single storey and no wider than half the width of the original house. Two-storey rear extensions can extend up to 3 metres and must be at least 7 metres from the rear boundary. The rules have several detailed conditions, so always get your design checked before you build.
When You DO Need Planning Permission
- Your design is bigger than the PD limits above.
- Your home is a listed building, or in a conservation area where an Article 4 direction has removed PD rights.
- Your property is a flat or maisonette.
- The extension is at the front of the house facing a road.
Building Regulations Are Always Required
Even when planning permission is not needed, building regulations approval always is. This covers structure, fire safety, insulation, ventilation, drainage and electrics, and your extension is inspected as work progresses. Never skip it – you will need the completion certificate when you sell your home.
Party Wall Agreements
If your extension involves work on or near a shared wall or boundary, you may need to serve a party wall notice on your neighbours before work starts. This is a legal process separate from planning, and we can guide you through it.
Get a Lawful Development Certificate
Even when your extension is permitted development, we recommend applying for a Lawful Development Certificate from your council (for example the London Borough of Hillingdon in Hayes). It is written proof that your extension is lawful – very useful when you come to sell.
How Akaal Construction Can Help
We design, draw and build extensions across Hayes and West London, and we can check whether your idea fits permitted development or needs a planning application. Read our full Home Extension Guide, or book a free site survey – call 07587 722142.