Many single-storey rear extensions need no planning permission under permitted development: up to 4 metres deep on a detached house or 3 metres otherwise, no more than 4 metres high, and eaves no higher than 3 metres within 2 metres of a boundary. Conservation areas, flats and Article 4 Directions change the rules.
Many single-storey rear extensions in England do not need planning permission at all, thanks to permitted development rights. According to the Planning Portal’s single-storey extension guidance, a detached house can extend up to 4 metres beyond the original rear wall, and a semi-detached or terraced house up to 3 metres, without a planning application, provided the extension meets a set of other conditions on height and boundary distance.
The limits that apply
| Rule | Limit |
|---|---|
| Depth, detached house | Up to 4 metres beyond the original rear wall |
| Depth, semi-detached or terraced house | Up to 3 metres beyond the original rear wall |
| Maximum overall height | 4 metres |
| Eaves height within 2 metres of a boundary | No more than 3 metres |
| Distance from the rear boundary | Must not come within 7 metres of it |
Extensions bigger than the standard permitted development limits (up to 8 metres deep for a detached house, or 6 metres for a semi-detached or terraced house) are still possible without full planning permission, but they go through a prior approval process instead, which involves formally notifying your neighbours and giving the council a chance to object before work can start.
What else has to be true for permitted development to apply
Depth and height are not the only conditions. Permitted development for a single-storey rear extension also generally requires:
- No more than half the garden (measured from the original house) to be covered by extensions and outbuildings once the new build is complete
- Materials that are similar in appearance to the existing house, if it is not attached to the side or is otherwise visible from a road
- No verandas, balconies or raised platforms as part of the extension
- Side facing windows to be obscure glazed and non opening below 1.7 metres, if applicable
Every one of these conditions has to be met, not just the headline depth and height figures, so it is worth checking the full guidance or getting a builder or architect who knows the rules to confirm your specific plans qualify.
When you need to apply for planning permission anyway
Permitted development rights do not apply everywhere or to every property. You will usually need full planning permission if:
- Your property is in a conservation area, is listed, or sits within an Article 4 Direction area, where the council has specifically removed some permitted development rights.
- The extension exceeds the depth, height or coverage limits above.
- You live in a flat or maisonette. Permitted development rights for extensions generally apply to houses, not flats.
- Permitted development rights were removed as a condition of an earlier planning permission, which sometimes happens on newer estates.
If any of that applies, or you are simply not sure, the Planning Portal explains the Lawful Development Certificate, which is a way to get formal, written confirmation from your council that a specific extension does not need planning permission, which is worth having on file, especially when you come to sell. This is exactly the kind of thing that trips people up in conservation-heavy towns like High Wycombe, where an Article 4 Direction can remove rights a neighbouring street still has.
Building regulations still apply either way
Whether or not you need planning permission, almost every extension needs building regulations approval, which is a completely separate process covering structural safety, insulation standards, fire escape routes, and drainage. Skipping planning permission because your extension is permitted development does not mean skipping this step. A builder worth hiring will tell you clearly which of these apply to your specific job and who is responsible for arranging sign-off, rather than leaving you to find out later.
Getting this right before you commit to a design
Confirming your extension genuinely qualifies for permitted development before you commission drawings or get quotes saves real time and money if it turns out you need to apply after all. A good builder or architect will check this as a first step, not an afterthought. We check trading history and track record when we research our Top 5 pages of builders for every town, so a page for somewhere like Barnstaple is a fast way to shortlist people who handle this properly.
Frequently asked questions
How far can a single-storey rear extension go without planning permission?
Under permitted development, a single-storey rear extension on a detached house can extend up to 4 metres beyond the original rear wall, and up to 3 metres on a semi-detached or terraced house, according to the Planning Portal. Going further than this is still possible but requires either full planning permission or a prior approval application under the neighbour consultation scheme.
What is the maximum height for a permitted development extension?
A single-storey rear extension must not exceed 4 metres in overall height. If any part of it is within 2 metres of a boundary, the eaves height at that point must be no more than 3 metres.
Does a permitted development extension still need building regulations approval?
Yes, always. Permitted development only removes the need for planning permission. Building regulations approval, covering structural safety, insulation, fire escape and drainage, applies to virtually every extension regardless of its planning status, and is arranged separately.
What is an Article 4 Direction and how do I know if it affects me?
An Article 4 Direction is a local council order that removes some or all permitted development rights in a specific area, often conservation areas or estates with a uniform character the council wants to protect. It means work that would normally not need planning permission does need it. Check with your local planning authority or search the Planning Portal before assuming permitted development applies to your property.
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About the author
Stu Clark
Stu spent over 15 years in the trades, working as a plumber before running his own plumbing and bathroom renovation company with a team of eight. He founded Top5Trades to give homeowners the kind of shortlist and straight advice you would get from someone who has actually done the work. More about us →