Plenty of extensions don't need a planning application at all. Houses in England come with permitted development rights: a national set of rules allowing certain extensions and alterations without applying to the council. The catch is that the rules are detailed, and plenty of homes have fewer rights than their owners think.
First: does your home have permitted development rights?
Permitted development applies to houses. It doesn't apply to:
- flats and maisonettes, which need planning permission for almost any extension
- homes where an earlier planning permission removed the rights by condition (common on newer estates)
- areas covered by an Article 4 direction that takes particular rights away
Listed buildings are a separate case: whatever the planning position, almost any extension or alteration will need listed building consent. And in a conservation area or National Landscape (such as Dedham Vale), some of the rights below are narrower.
Single-storey rear extensions
Under permitted development, a single-storey rear extension can usually go out:
- up to 3 metres from the original rear wall of a semi-detached or terraced house
- up to 4 metres on a detached house
There's also a larger home extension route that allows up to 6 metres (semi or terrace) or 8 metres (detached). You have to notify the council first, it writes to the neighbours, and it has 42 days to decide whether the effect on their amenity is acceptable. This route isn't available in conservation areas or National Landscapes.
The height limit is 4 metres, and if the extension is within 2 metres of a boundary the eaves can be no higher than 3 metres.
Side extensions
A single-storey side extension can be permitted development if it's no more than 4 metres high and no wider than half the width of the original house. Side extensions aren't permitted development in a conservation area or National Landscape.
Two-storey extensions
A two-storey rear extension can only go out 3 metres, must be at least 7 metres from the rear boundary, and the roof pitch should match the house. In practice most two-storey extensions need planning permission.
Loft conversions
A loft conversion with rear dormers can often be done under permitted development, within a volume limit of 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached houses. Dormers facing the road, raising the ridge, or a loft in a conservation area all need planning permission. See our page on loft and dormer conversions.
Rules that apply to everything
- The original house is the house as it was first built (or as it stood on 1 July 1948). Earlier extensions count towards the limits.
- Extensions and outbuildings together can't cover more than half the garden around the original house.
- Nothing can go forward of the front of the house facing a road.
- Materials should be similar in appearance to the existing house.
- Balconies, raised verandas and platforms over 30cm high aren't permitted development.
Getting it in writing
If you build under permitted development, it's worth applying for a lawful development certificate. It's the council's formal confirmation that the work is lawful, and solicitors often ask for it when you come to sell.
And remember that permitted development is about planning only. Most extensions still need building regulations approval.
When you need planning permission
If your extension goes beyond these limits, it isn't the end of the road; it means a householder planning application. Many larger extensions are approved, especially when the design responds well to the house and the neighbours.
Book a free home visit
The quickest way to know where you stand is to have someone look at the house. Ben will visit, check your property's planning history and designations, and tell you honestly whether your extension needs permission and what's likely to be approved.
Every site is different. This guide is general information, not advice on your project. For a straight answer about your property, book a free home visit: Ben will come and look, with no obligation.
Who'll handle your project: Benjamin Plunkett, our Managing Director and Planning & Heritage Consultant, is your point of contact from the first site visit to the decision. Charlie Plunkett MCIAT produces the drawings.
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