Do You Need Planning Permission for an Extension?
Permitted development, prior approval and full applications, explained properly, with the traps that catch people in Colchester.
Most single storey extensions do not need planning permission. That is the short answer, and it is true often enough to be useful and wrong often enough to be dangerous. This guide explains how the system actually works, so you can tell which side of the line your project sits on before you spend money on drawings.
Two separate systems, frequently confused
Planning permission and Building Regulations are different things, run by different teams, with different applications and different fees.
Planning is about whether you may build: the size, the position, the effect on neighbours and the appearance. Building Regulations are about how it is built: structure, insulation, fire safety, drainage, ventilation.
You can have planning permission and still fail Building Control. More importantly, work that needs no planning permission at all still needs Building Regulations approval. Nobody is ever exempt from the second because of the first.
Permitted development
Permitted development rights are a national grant of planning permission for certain types of work. If your extension complies with every condition, you do not apply, because permission already exists.
The conditions are specific and cumulative. Miss one and the whole thing needs an application.
Depth
For a single storey rear extension the depth limit is measured from the original rear wall of the house. A detached house is allowed more than a semi or a terrace. Both limits roughly double through the prior approval route described below.
Height
Overall height is capped, and there is a separate lower cap on eaves height where any part of the extension comes within two metres of a boundary. On a narrow plot the eaves rule frequently determines the roof design.
Width and side extensions
A side extension is limited to half the width of the original house and must be single storey, with its own height cap.
Two storey extensions
These have their own conditions: a shallower depth limit than single storey, a minimum distance from the rear boundary, and a requirement that the roof pitch matches the existing house where practicable.
Materials and position
Materials must be similar in appearance to the existing house. The extension must not extend beyond a wall forming the principal elevation of the original house, and separately must not extend beyond a wall that fronts a highway and forms a side elevation. Those are two distinct limbs, and only the second one mentions a highway. The distinction matters on a corner plot, or on a house turned side on to the road, where the wall you think of as the back can be the wall the rules treat as the front. It is also why front extensions and porches are treated separately and tightly.
The word that catches almost everybody
Original. Depth is measured from the house as it was originally built, or as it stood on 1 July 1948 if it is older than that. Not from the wall you have today.
If a previous owner added a small extension in the 1990s, that depth has already been consumed. It counts against your allowance even though you did not build it, and you may have very little left, or none.
This is the single most common reason a project that “definitely does not need permission” turns out to need one. It is checked by looking at the planning history for the address, not by looking at the house.
The Larger Home Extension prior approval route
If you want to go deeper than the standard permitted development limit, there is a middle path between permitted development and a full application.
You notify the council of what you intend to build. The council writes to the adjoining neighbours and gives them a period to object. If nobody objects, you may proceed. If somebody does, the council considers whether the impact on their amenity is acceptable and decides.
The process runs to 42 days. It is not a planning application, the fee is lower, and the council is only allowed to consider the impact on neighbouring amenity rather than the whole range of planning matters. But it is not automatic either, and a neighbour with a genuine daylight complaint can stop it.
What removes your permitted development rights, and what adds a second hurdle instead
- Flats and maisonettes. Permitted development for extensions applies to houses. If you own a flat, you are applying.
- Listed buildings, which are the exception on this list. Listing does not remove your permitted development rights, which is the single most repeated mistake on this subject. What it does is add a second consent: listed building consent, covering the inside as well as the outside, under separate legislation, where unauthorised work is a criminal offence rather than a planning irregularity. In practice that second consent is the harder of the two, which is why people assume the first one is gone.
- Article 4 directions. These remove specified permitted development rights across a defined area. They are property specific and worth checking rather than assuming.
- Previous removal by condition. Newer estates in particular often had permitted development rights removed by a condition on the original planning permission for the estate. This is extremely common on housing built from the 1980s onwards and almost nobody checks it.
Conservation areas
A conservation area does not remove permitted development entirely, but it restricts it. Side extensions generally lose permitted status. Cladding usually requires consent. Rooflights are the one people get told wrongly: a rooflight sitting in the plane of the roof slope is not removed by the designation on its own, though a dormer is. And the council will take a view on materials and detailing rather than only on size and position.
Colchester has a substantial number of conservation areas, including the historic core, the Dutch Quarter, part of Lexden, and village centres such as Dedham and Wivenhoe. Coggeshall, which has one of the finest in the county, falls to Braintree District rather than Colchester. The boundaries are specific and rarely follow the roads you would expect.
What neighbours can and cannot do
Neighbours are consulted on a planning application and can object. They cannot veto it. An objection only carries weight where it raises a genuine planning consideration, and a surprising amount of what people object about is not one.
Material considerations include loss of daylight or sunlight, overlooking and loss of privacy, an overbearing or enclosing effect, highway safety, parking, noise, and the effect on the character of a conservation area. These are weighed by the officer and can lead to a refusal or to a condition.
Not material considerations, whatever anybody feels about them: loss of a view, effect on property value, the identity of the applicant, disruption during construction, competition with an existing business, or a private boundary dispute. A boundary disagreement is a legal matter between the two of you and the council has no role in it.
| Material consideration | Not a material consideration |
|---|---|
| Loss of daylight or sunlight | Loss of a view |
| Overlooking and loss of privacy | Effect on property value |
| An overbearing or enclosing effect | Identity of the applicant |
| Highway safety and parking | Disruption during construction |
| Noise | Competition with an existing business |
| Effect on a conservation area | A private boundary dispute |
The practical advice is unglamorous and it works: tell your neighbours yourself, before the letter arrives from the council. Show them the drawings. An objection is far more often a reaction to being surprised than a considered planning argument, and once it is submitted it sits on the public file whether or not they later change their mind.
None of this touches the Party Wall etc. Act 1996, which is entirely separate from planning. Party wall notices are a legal requirement in their own right, triggered by cutting into a shared wall, building on the boundary line, or excavating near a neighbour’s foundations, and they apply whether or not you needed planning permission.
Covenants, which are not planning at all
A restrictive covenant on the title is private law between you and whoever holds the benefit of it. The council does not check covenants and will happily grant permission for something your deeds forbid.
They are common on estate housing from the 1980s onwards, and on land sold off by a former estate. Some require the consent of a management company or the original developer before any alteration. Check the deeds early, because a covenant can stop a project that has full planning permission.
The Lawful Development Certificate
Where your extension genuinely is permitted development, you can apply for a Lawful Development Certificate. The council confirms formally that the work does not require planning permission.
It is not compulsory. Apply for it anyway. It costs a fraction of a planning fee, and it is the document that proves the extension was lawful when a buyer’s solicitor asks about it in ten years’ time. Without one you are relying on your own recollection and the goodwill of a conveyancer.
If you do need a full application
A householder planning application has a statutory determination period of eight weeks, and that clock only starts once the application has been validated, which can itself take a week or two if anything is missing.
You will need existing and proposed plans and elevations to a proper scale, a site location plan, and the fee. Neighbours are consulted and can comment. Most householder applications are decided by planning officers under delegated powers rather than by committee.
If it is refused, you can amend and resubmit, or appeal to the Planning Inspectorate. Appeals take months. Amending and resubmitting is usually faster and often better, because a refusal notice tells you exactly what the objection was.
Nobody can promise you a planning outcome. Anyone who tells you they will get your application approved is telling you something they cannot know. What can be done is designing to the local plan policies from the start, and dealing with the likely objections in the application rather than after the refusal.
Loft conversions, garages and outbuildings
Extensions are not the only permitted development category, and the rules differ.
A loft conversion is usually permitted development, subject to a volume allowance measured in cubic metres rather than depth: broadly 40 cubic metres of additional roof space for a terraced house and 50 for a semi or detached. The allowance is cumulative across everything already added to the roof. Dormers must not be on the principal elevation facing a highway, and must be set back from the eaves. Side facing windows in the new roof space must be obscure glazed and non opening below 1.7 metres from the floor, and that condition applies everywhere rather than only in a conservation area. On designated land, including a conservation area, the roof-enlargement right does not apply at all, so a dormer there is a full application whatever the volume.
A garage conversion where nothing changes externally often needs no planning permission at all, because it is a change of use within the existing envelope. It absolutely does need Building Regulations approval, because the floor, the walls and the insulation all have to be brought up to habitable standard. Where the garage door is replaced with a wall and a window, the materials condition applies.
An outbuilding or garden room sits under a different class of permitted development. It must be single storey, height limited depending on the roof type and its distance from a boundary, and it must be incidental to the enjoyment of the house. That word incidental matters: an outbuilding used as a self contained annexe with someone sleeping in it is a separate dwelling, which needs planning permission and may trigger a Community Infrastructure Levy charge.
Building Regulations, whichever route you take
Whatever the planning answer, the Building Regulations answer for an extension is always the same: yes.
You choose between a full plans submission, where the drawings and structural calculations are checked before you start and you get a decision notice, and a building notice, where you tell the council you are starting and they inspect as the work proceeds.
Full plans takes longer at the front end and removes almost all the risk of an expensive disagreement halfway up a wall. On anything with a structural opening in it, that is the route worth taking.
At the end you receive a completion certificate. Keep it with the deeds. It is the document a buyer’s solicitor will ask for, and an extension without one causes real problems at sale long after everyone has forgotten the job.
So do you need it?
Work through it in this order:
- Is it a flat or maisonette? If so, you are applying. Is it listed? Permitted development still applies, but you need listed building consent as well, and that is the harder of the two.
- Is there an Article 4 direction, or a condition on the original permission removing permitted development rights? Check with the council.
- Is it in a conservation area? If yes, your rights are reduced and cladding or a side extension will need consent.
- Has the house been extended before? Find out what remains of the original allowance.
- Does the proposal fit inside every permitted development condition, not just the depth one?
- If it fits, apply for a Lawful Development Certificate. If it does not, either redesign to fit, use the prior approval route for extra depth, or make a full application.
- Separately, check the deeds for covenants.
We do this check on every job before anybody draws anything, because the answer determines the design rather than the other way round.
The limits and routes described here change from time to time, and how they apply depends on your specific property, its planning history and its designation. Treat this as an explanation of how the system works rather than as confirmation of what you can build.
Last reviewed August 2026. Planning and Building Regulations change, and your property may differ.
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