Do you need planning permission for an extension?
The permitted development limits for extensions in England, what needs prior approval, and what removes the right entirely. Written for West Yorkshire homeowners.
Most single-storey extensions in England do not need planning permission. They are built under permitted development — a national grant of permission that applies as long as the extension stays inside a set of limits. Go past any one of them and you need a full application.
The limits are specific and unforgiving. They are also not the whole story: several things remove permitted development rights entirely, and one of them applies to a lot of houses in Leeds and Bradford. This page sets out what the rules actually say.
Single-storey rear extensions
The depth allowed from the original rear wall depends on the house type. A detached house gets 4 metres. Everything else — semi-detached, terraced, end-terrace — gets 3 metres.
Height is capped at 4 metres overall, and if the extension comes within 2 metres of a boundary the eaves cannot go above 3 metres. That second limit catches more extensions than the first, because most rear extensions on a terrace are hard against at least one boundary.
The limits in full
- 4m deep on a detached house, 3m on any other house
- 4m maximum height
- 3m maximum eaves height within 2 metres of a boundary
- Not forward of the principal elevation facing a highway
- Materials of similar appearance to the existing house
- No verandas, balconies or raised platforms
Going deeper: the prior approval route
A deeper single-storey rear extension is still possible without a full planning application — 8 metres on a detached house, 6 metres on any other house — but it has to go through prior approval under the neighbour consultation scheme.
The council notifies the adjoining neighbours. If none of them objects within the consultation period, the extension proceeds. If one does, the council decides whether the impact on their amenity is acceptable. It is not a planning application and the council cannot refuse it on design grounds — but it is a decision, it takes time, and it has to be applied for before work starts, not after.
Two-storey and side extensions
A two-storey rear extension can project 3 metres and no further, and there must be at least 7 metres between the extension and the boundary opposite the rear wall. The roof pitch has to match the existing house as far as practicable, and any upper-floor window in a side elevation must be obscure-glazed and non-opening below 1.7 metres.
A side extension has to be single storey, no more than 4 metres high, and no wider than half the width of the original house. On designated land it needs full planning permission whatever its size.
The 50 per cent rule catches people out
No more than half the land around the original house can be covered by buildings. "Original house" means as it was on 1 July 1948, or as first built if later — not as you bought it.
This matters on a house that has already been extended. A previous owner's conservatory, an outbuilding, a garage: all of it counts against the allowance, and it is the reason a proposal that looks well inside the depth limits sometimes is not permitted development at all.
What removes the right entirely
Permitted development is not universal. Several categories of property have no householder rights at all, and in some areas the council has removed them.
No permitted development rights
- Flats and maisonettes — always a planning application
- Houses created by a permitted development conversion from another use
- Designated land: conservation areas, National Parks, AONBs, the Broads and World Heritage Sites — side extensions and some rear extensions need permission
- Listed buildings — listed building consent is needed as well as, and separately from, planning permission
- Anywhere covered by an Article 4 direction removing the relevant right
- New estates where rights were removed by a planning condition on the original consent — this is common and is easy to miss
Get it in writing
If the extension is permitted development, apply for a Lawful Development Certificate anyway. It is not compulsory. It is also the only document that proves, to a buyer's solicitor in ten years' time, that the extension was lawful when it was built.
Without one the burden falls on whoever is selling. Indemnity insurance and a nervous buyer cost more than the certificate did.
Planning permission is not building control
They are two separate approvals and neither substitutes for the other. Planning is about what the building looks like and how it affects the area. Building control is about whether it is structurally sound, insulated, drained, ventilated and safe.
An extension can be permitted development and still need full building regulations approval. Almost all of them do.
Where this comes from
Everything on this page was checked against the primary source in September 2026. Regulations, designations and thresholds change, and nothing here is a substitute for advice on your own property or contract. If you spot something that has moved, tell us and we will correct it.
The sources are listed opposite. They are the published guidance and legislation themselves rather than a summary of them, so you can check any of it directly.
Common questions
Questions on this
Does a conservatory count towards the 50 per cent?
Yes. Anything built on the land around the original house counts, including outbuildings, garages and previous extensions, whoever built them. The test is the footprint on the plot, not who put it there or when.
My neighbour built a 6-metre extension. Can I?
Possibly, but their extension is not evidence. They may be detached where you are semi-detached, they may have gone through prior approval, they may have had a full planning permission, or they may have built it without either. The only thing that settles it for your house is your house.
How long does prior approval take?
The council has 42 days from a valid application. You cannot start before you have the decision or the 42 days have run out without one, and starting early is the one mistake that cannot be corrected afterwards.
Is a lawful development certificate worth applying for?
Yes. It costs a fraction of a planning application and it is the document that proves the extension was lawful. The alternative is explaining it to a buyer's solicitor with nothing in writing.
Where this applies
The work this affects
- Home extensions Single and two-storey rear, side and wraparound extensions, from first survey to building control sign-off.
- Loft conversions Dormer, hip-to-gable and rooflight conversions, including the structural work and the staircase.
- Full house renovations Whole-property refurbishment — strip out, first fix, second fix and finishes under one contract.
Start a conversation about your project
Tell us what you are planning. We will come out, look at it properly, and put a written quotation in front of you.