Guide

Do I need planning permission for an extension?

Often not. A lot of extensions are already permitted under national rules called permitted development — but those rules are a list of limits, and one broken limit means a planning application. Whether your house has those rights at all depends on the property, not on the design.

The short answer

Permitted development is a national grant of planning permission.

It sits in Schedule 2, Part 1, Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015. If your extension stays inside every limit in Class A, you do not need to apply for planning permission.

Break one limit and the whole thing needs a householder planning application.

Three things decide the answer for your house:

What type of house it is. Detached houses are allowed more than semi-detached, terraced and end-of-terrace.
What has already been built on the plot. Previous extensions and outbuildings count against you.
Whether the property is designated. Conservation area, listed, an Article 4 direction, or a flat — any of these changes the answer, and two of them remove the rights entirely.

The rest of this page goes through each in turn.

Single-storey rear extension: what the rules actually allow

For a single-storey extension off the back of the house, all of the following have to be true:

Depth. No more than 4 metres beyond the rear wall of the original house if it is detached, or 3 metres for any other house — semi-detached, terraced or end-of-terrace. Depth is measured from the base of the original rear wall to the outer face of the new wall, not counting guttering or barge boards.
Height. No more than 4 metres overall, and no higher than the highest part of the existing roof. On a bungalow, that second rule bites well before 4 metres.
Eaves. No higher than the eaves of the existing house. And if any part of the extension comes within 2 metres of a boundary, the eaves cannot exceed 3 metres.
Ground cover. Everything within the grounds other than the original house — extensions, garage, sheds, garden room — must not together cover more than half the land around the original house.
Materials. The outside has to be of similar appearance to the existing house.
Position. Nothing may project beyond the principal elevation, or beyond a side elevation that fronts a highway.
No verandas, balconies or raised platforms.

"Original house" has a specific meaning: the house as it was built, or as it stood on 1 July 1948 if it is older than that. Not as you bought it.

Side extensions and two-storey extensions

Side extensions are tighter. Single storey only, no more than 4 metres high, and no wider than half the width of the original house. A two-storey side extension always needs planning permission.

Two-storey and more-than-one-storey rear extensions must not go more than 3 metres beyond the rear wall of the original house, and must not come within 7 metres of the boundary opposite that rear wall. That 7-metre rule is what stops most two-storey rear extensions on ordinary suburban plots around Caterham, Redhill and Purley, where back gardens are not deep.

Two further conditions apply to anything above ground floor: the roof pitch should match the original house as far as practicable, and any side-facing upper windows must be obscure-glazed and fixed shut unless the opening part is more than 1.7 metres above floor level.

Going deeper: the Larger Home Extension route

There is a second route that doubles the depth. A single-storey rear extension can go up to 8 metres on a detached house, or 6 metres on any other house, if you notify the council first and go through prior approval — often called the neighbour consultation scheme. The 4-metre height limit still applies.

This route is not available if the house is on designated land or a Site of Special Scientific Interest.

It works like this:

You send the council a written description of the work — how far it goes beyond the rear wall, its maximum height, its eaves height — plus a plan of the site, the addresses of adjoining properties, and your contact details. A fee is payable.
The council writes to each adjoining owner or occupier, giving them at least 21 days to make representations.
If nobody responds, prior approval is not required and you can build.
If somebody does respond, the council considers the effect on the amenity of all adjoining properties, not only the ones that wrote in.
You can start once you have written notice that prior approval is not required, or written prior approval, or 42 days have passed since the council received your information — whichever comes first.

Build it as described. This was a temporary right originally; it was made permanent in 2019.

What removes permitted development altogether

Some properties never had these rights, and some have had them taken away.

Flats and maisonettes. Permitted development for extensions applies to houses only. A flat has no such rights, ever. Neither does a house created by a permitted development change of use.
Article 4 directions. A council can withdraw permitted development rights across an area. In Reigate and Banstead, Article 4 directions have been served on most conservation areas in the borough, controlling external changes to houses. Tandridge publishes its Article 4 areas as an open dataset you can search by address.
Conditions on the original permission. Newer estates frequently have permitted development rights removed by a condition on the planning permission that created them. This catches people out constantly, because nothing about the house looks different.
Designated land — a conservation area, a National Landscape (formerly AONB), a National Park or a World Heritage Site. Here you cannot build a side extension, cannot build a more-than-one-storey rear extension, cannot clad the outside, and cannot use the Larger Home Extension route at all.
Listed buildings. Listed building consent is a separate consent from planning permission, and it is a criminal offence to do the work without it. Listing covers the interior as well as the outside, plus objects fixed to the building and structures that have stood in the grounds since 1948.
A house already extended. Previous extensions count towards the limits, whether they were built under permitted development or with planning permission. A semi already extended 2 metres has 1 metre left.
Covenants. A restrictive covenant on your title can stop you building even where planning is not an issue. It is private law, not planning — the council will not check it and planning permission does not override it. Your solicitor or your deeds will tell you.

One that does not remove these rights: Green Belt. Much of Tandridge and Reigate and Banstead is Green Belt, and it is not designated land for permitted development purposes. It matters a great deal if you have to make a planning application; it does not remove householder permitted development.

Why a Lawful Development Certificate is worth having anyway

If the work is permitted development, you do not need permission — but nobody has said so in writing, and in ten years' time you will need somebody to have said so.

A Lawful Development Certificate is the council's formal, legally binding confirmation that what you have built, or what you propose to build, is lawful. There are two kinds: one for existing work, one for proposed work. It is not compulsory.

It earns its money at three moments: when you sell and the buyer's solicitor asks what permission the extension had; if a neighbour complains and the council's enforcement team turns up; and if a lender or insurer queries the work. The fee for a proposed-use certificate is half the fee for the equivalent planning application, which makes it substantially cheaper than the argument it prevents.

Apply to your own council, through the Planning Portal. The council decides it on the facts and the law — not on whether it likes the design.

Which council you deal with

Most of the homes we work on sit in one of two districts.

Tandridge District Council covers Godstone, Oxted, Caterham, Warlingham, Woldingham, Lingfield, Bletchingley, Tandridge, Limpsfield, Blindley Heath, Outwood, Crowhurst, Dormansland and Whyteleafe. Tandridge has 19 conservation areas, including Godstone Church Town, Godstone The Green, Oxted, Station Road West Oxted, Broadham Green and Spring Lane Oxted, Limpsfield Village, Lingfield, Bletchingley, Brewer Street and Place Farm, Woldingham Green, Chaldon, Outwood, Burstow, Caterham Barracks, Kenley Aerodrome, Pendell, South Park, Great Farleigh Green and Fickleshole. Two National Landscapes also cover parts of the district: the Surrey Hills across much of the north, the High Weald in the south-eastern corner.

Reigate and Banstead Borough Council covers Redhill, Reigate, Horley, Merstham, Banstead, Tadworth, Kingswood, Chipstead, Walton-on-the-Hill, Earlswood, Salfords and Smallfield. Article 4 directions apply to most of its conservation areas. Part of the Surrey Hills National Landscape falls inside the borough too, around Reigate Hill, Colley Hill and Gatton Park.

Around the edges of our patch you may be dealing with Croydon (Purley, Coulsdon, Kenley), Mole Valley (Charlwood), Sevenoaks (Edenbridge, Westerham), Mid Sussex (East Grinstead, Felbridge) or Crawley.

Every one of these councils has an address search on its website that shows conservation area, Article 4 and listing status for your specific property. Check yours before you draw anything. The national rules are the same everywhere; what is designated is not.

Planning permission is not the only permission

Two things sit alongside it and are often confused with it.

Building regulations apply to an extension whether or not it needs planning permission. They cover structure, insulation, drainage, fire safety and ventilation, and they are approved and inspected separately.

The Party Wall etc. Act 1996 applies if you are building on or near a shared boundary, cutting into a party wall, or excavating close to a neighbour's foundations. You serve notice on the neighbour yourself; the council has nothing to do with it.

If you are weighing up an extension on a house in our area and want to know which of these apply before you spend money on drawings, call us on 01883 337 700. We will tell you what we can see and what needs checking with the council — we price the work once we have seen it.

Common questions

Q.01How far can I extend without planning permission?

For a single-storey rear extension, 4 metres beyond the original rear wall on a detached house, or 3 metres on a semi-detached, terraced or end-of-terrace house, with a 4-metre height limit. That doubles to 8 metres and 6 metres respectively if you use the Larger Home Extension prior approval route, which is not available on designated land. Every other Class A limit still has to be met — height, eaves, the half-the-garden rule, materials and position.

Q.02My neighbour objects to my prior approval application. Does that stop the extension?

Not by itself. Once representations are received, the council assesses one thing: the effect on the amenity of adjoining properties. It is not a vote, and general objection to the idea of an extension is not the test. The council must consider all adjoining properties, including those that did not write in, and it must decide within 42 days of receiving your information.

Q.03I'm in the Green Belt. Does that mean I need planning permission for an extension?

No. Green Belt is not designated land for permitted development purposes, so it does not remove your householder rights. Conservation areas, National Landscapes, National Parks and World Heritage Sites do. Green Belt becomes very important if your extension falls outside permitted development and you have to apply for planning permission.

Q.04My house has already been extended. Do the limits start again?

No. Previous extensions count towards the limits, whether they were built under permitted development or with planning permission. The measurement is always taken from the original house — as built, or as it stood on 1 July 1948 if it predates that. A semi already extended 2 metres to the rear has 1 metre of permitted development left.

Q.05If I don't need planning permission, should I still apply for a Lawful Development Certificate?

It is not compulsory, but it is usually worth it. Without one, there is no document anywhere saying the extension was lawful, and that gap surfaces when you sell, when a neighbour complains, or when a lender asks. The fee for a proposed-development certificate is half the equivalent planning application fee, and the council's decision is legally binding.

Q.06Can I extend a flat or maisonette under permitted development?

No. Permitted development rights for extensions apply to houses only — flats and maisonettes have never had them, and neither do houses created through a permitted development change of use. Any extension or alteration to a flat needs a planning application. You will also need to check your lease and get the freeholder's consent, which is a separate matter from planning.

Where this came from

Sources

Rules change. These are the pages this guide was written from — check them against your own property before you act on anything here.

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