Prior Approval vs Planning Permission for Extensions
Prior approval is not planning permission. See how it differs from permitted development and full planning for a rear extension in England: fees, timings, appeals.
Prior Approval vs Planning Permission for Extensions
Prior approval and planning permission are two different routes. Planning permission asks the council whether your extension is acceptable overall. Prior approval applies to a project that already has permission from national rules (permitted development), and asks the council to check only a short, fixed list of matters before you build. For a single-storey rear extension in England, the route you need depends mainly on how far the extension projects, and on whether anything has removed your permitted development rights.
TL;DR
- Permitted development is the permission itself, granted nationally. Prior approval is a check the council makes on certain permitted development projects. Planning permission is a full application judged on local and national policy.
- For a single-storey rear extension, prior approval comes into play when it goes beyond 4m (detached) or 3m (other houses), up to 8m or 6m, under the neighbour consultation scheme.
- Prior approval costs £249 and takes 42 days for larger rear extensions. Householder planning permission costs £272 to £548 and is usually decided within 8 weeks.
- Article 4 directions, planning conditions, flats and listed buildings can take permitted development away, and then full planning permission is the route.
- Never start work before the council has issued its decision on a prior approval.
Table of Contents
- The three terms, in plain English
- How the two routes compare
- When a rear extension needs prior approval
- What the council can and cannot consider
- Timing, refusals and appeals
- When you need full planning permission instead
- Prior approval does not prove your extension is lawful
- Which route is better for you?
- How we handle it at The Extension Works
- Our perspective
- FAQ
- Sources
The three terms, in plain English
These words get used loosely, even by builders, so it helps to separate them.
Permitted development (PD) means certain building work can go ahead without a planning application. These rights are granted by Parliament and set out in the General Permitted Development Order. The government’s technical guidance for householders explains that the rights exist so householders can improve and extend their homes without applying where the impact is limited.
Prior approval is not a separate kind of permission. It is a condition attached to some permitted development rights: before you build, you tell the council about the project and it gets an opportunity to assess whether the works meet the conditions in the Order. You are not asking whether the council likes your extension. You are asking whether it raises any problem on the specific matters the Order lets the council examine.
Planning permission (for a house, a householder application) is the full route. The council weighs the proposal against its local plan, design policies and neighbour impact. Householder planning permission is usually needed when a proposal does not meet the permitted development rules, or when those rights have been restricted or removed.
A useful way to hold it in your head: permitted development is the door, prior approval is a quick check at the door for some projects, and planning permission is the alternative door when the first one is closed.
How the two routes compare
| Permitted development, no prior approval | Prior approval | Householder planning permission | |
|---|---|---|---|
| Typical rear extension | Up to 4m (detached) or 3m (other houses) | More than 4m and up to 8m (detached), more than 3m and up to 6m (other houses) | Anything outside the PD limits |
| What the council looks at | Nothing in advance | Only the matters named in the Order | Local plan policy, design, neighbour impact, and more |
| Can the council refuse in principle? | Not applicable | No, the principle is already granted | Yes |
| Fee | None for the permission itself | £249 | £272 to £548 depending on the work |
| Usual wait | None | 42 days for larger rear extensions | Usually within 8 weeks |
The fees and timings come from Northumberland County Council’s householder guidance. Fees are set nationally in England, but they are revised from time to time, so check the current figure on the Planning Portal or your council’s page before you apply. Our own guide to planning fees for an extension goes through what each route costs.
When a rear extension needs prior approval
The standard single-storey rear extension right has size limits. Stay within them and no application is needed. Our permitted development rules page and the article on how big a rear extension can be under permitted development set out the full list of limits, including height and boundary conditions.
Go further and you enter the larger home extension route. Prior approval is required for a single-storey rear extension more than 4m but less than 8m for a detached house, or more than 3m but less than 6m for any other house. This is the neighbour consultation scheme. Prior approval is also required for upward extensions that add storeys, though that is a different job from a rear extension.
What actually happens
You submit basic information about the extension, including site plans, and the council consults the neighbours who share a boundary with you. The process can last 42 days. If neighbours object, the council considers the effect on their amenity, such as overlooking or loss of light. If nobody objects, the council will usually only look at the other listed matters before deciding.
We have written a separate piece on whether the neighbour consultation scheme applies to your extension, and another on avoiding refusal and delay with a prior approval extension.
What the council can and cannot consider
This is the real heart of the difference, and the reason many homeowners prefer prior approval.
On a prior approval, the council can consider only the conditions set out in the Order for that type of development. It cannot reopen the principle of the extension, and it cannot apply local plan policies. Depending on the development type, the matters can include transport, flooding, contamination, external appearance and the impact on neighbour amenity. For a larger rear extension the decisive one is usually the effect on neighbours.
On a householder planning application the council has a far wider brief. Design, materials, street scene, character of the area, and the reasoning in local policy all count. That gives you more room for debate, and also more room for refusal. Two near-identical extensions can get different outcomes depending on the council and the street.
Timing, refusals and appeals
Waiting times are close, but they work differently.
- Larger rear extension prior approval: 42 calendar days.
- Upward extensions: 8 weeks, according to the same guidance.
- Householder planning permission: usually decided within 8 weeks, though complex cases can run longer by agreement.
A prior approval can be refused, and that surprises people. If the council refuses it, or fails to determine it in time, you have a right of appeal to the Secretary of State. Many prior approvals can also gain deemed consent if the council misses its deadline, but that depends on the proposal, so do not rely on silence. Ask the council to confirm in writing before you commit to a start date. Our planning permission timeline guide shows how these waits fit into the whole project.
One rule matters above all: work must not begin until the council has issued its determination. Prior approval also cannot be gained retrospectively, so apply before you build, not after.
When you need full planning permission instead
Prior approval is only open to you if permitted development applies in the first place. Check these before you plan anything.
- Article 4 directions. A council can remove permitted development rights in a defined area, often conservation areas. The government guidance tells homeowners to check whether an Article 4 direction or a planning condition has removed the rights.
- Planning conditions. Some estates were approved with conditions that took PD rights away. Look at the original permission for your house.
- Flats and maisonettes. Householder PD rights apply to houses. Changes and extensions to flats go through a full planning application.
- Listed buildings. Listed building consent may also be required on top of any planning route.
- A design that breaks the limits. If the extension is deeper, taller, or closer to the boundary than the Order allows, it falls outside PD altogether, and householder planning permission is usually the answer.
Note also that these are rules for England. Wales, Scotland and Northern Ireland each have their own permitted development arrangements, with different limits and procedures, so do not assume an English rule applies there.
Prior approval does not prove your extension is lawful
This is a trap. A prior approval decision tells you the council has no objection on the specific matters. It does not make the whole development lawful. If your extension breaks another PD condition, say on height or materials, you could still be in breach. Harrow Council points out that approval does not make a development lawful and recommends a Certificate of Proposed Lawful Development. A certificate is useful when you come to sell, because a buyer’s solicitor will want paperwork showing the extension was built within the rules.
Which route is better for you?
There is no universal winner. Use these questions.
- Does a standard-size extension give you enough room? Then permitted development without prior approval is the cheapest and quickest.
- Do you need extra depth? Prior approval gives you up to 8m or 6m with a narrow set of tests and a lower fee.
- Are you in a conservation area, a flat or a listed building? Expect full planning permission.
- Is the design ambitious or unusual? Planning permission lets you argue the merits, which prior approval does not.
- Do your neighbours have strong feelings? Under prior approval their objections only count if they concern amenity. Under planning permission any material planning concern counts.
Fee exemptions exist for both. Householder applications carry no fee if the work improves a disabled person’s access, safety, health or comfort, and for prior approval the exemption applies only to larger rear extensions and additional storeys.
How we handle it at The Extension Works
We design, get approvals for and build single-storey rear extensions, so the route question is one we settle for every customer at the start. We handle both Permitted Development and prior-approval routes, along with the plans, structural calculations and building control that go with them. Our instant quote tool lets you set up your extension online and see it in live 3D before you commit to anything.
If you book, the booking fee is £499, one-off. The price of the build itself is fixed and includes VAT, and the work carries a 12-month workmanship warranty. One in-house team looks after the project from the first sketches to final sign-off, with no sales visits.
When you are ready to see what your extension could look like and which route fits, start with the single-storey rear extension page.
Once the building work is done, a thorough clean makes a real difference to how the new space feels. This after builders cleaning checklist covers the dust control side of it.
Our perspective
Most homeowners come to us worried about the word “planning”. In our experience the worry is bigger than the reality. For a typical house in outer London or the South East, the question is rarely whether an extension is allowed. It is which route is the cleanest and how to keep the paperwork tidy.
We would steer you towards prior approval over a full application whenever your design allows it. The council’s questions are narrow and known in advance, and the fee is lower. What we would never do is treat approval as the finish line. The extension still has to meet every PD condition as built, and it still needs building control sign-off. That is why we keep design, planning and construction under one roof: the drawings the council sees are the drawings we build from.
And whichever route you take, find out about Article 4 directions on day one. It is the single most common reason a plan changes.
— Esskay
FAQ
How long does a prior approval application take?
For a larger single-storey rear extension the determination period is 42 calendar days. Upward extensions that add storeys take 8 weeks. The clock starts once the council has a valid application, so a complete set of plans avoids delay.
Can prior approval be refused?
Yes. The council can refuse if the extension fails one of the specific matters it is allowed to assess, such as the impact on neighbour amenity. If it refuses or does not decide in time, you can appeal to the Secretary of State. A refusal does not stop you applying again with a revised design.
Is prior approval the same as permitted development?
No. Permitted development is the right to build without a planning application. Prior approval is a step some of those rights require, giving the council a chance to check named matters first. A standard-size rear extension needs no prior approval, while a larger one does.
Do I need a certificate as well as prior approval?
It is not compulsory, but it is wise. Prior approval does not by itself confirm that the finished extension is lawful. A Certificate of Proposed Lawful Development gives you formal proof, which helps when you sell or remortgage.
Sources
- Householder planning permission, Northumberland County Council
- When is planning permission not needed? Permitted development, House of Commons Library
- Permitted development rights for householders: technical guidance, GOV.UK
- When is permission required? GOV.UK
- Prior approval for extensions and conversions, Harrow Council
- Types of planning applications, Brent Council