Do You Need Planning Permission for Your Extension?
How to tell whether your extension needs a planning application or falls under permitted development. Covers the two routes, when PD rights don't apply, and how to check your property.
You've decided you want an extension. Maybe it's a kitchen, maybe a rear living space, maybe a combination. Before you call an architect or start browsing bifold doors, there's a question you need to answer first: do you need planning permission?
Getting this wrong isn't a bureaucratic inconvenience. Your local council can issue an enforcement notice requiring you to demolish the work and restore the site to its original state. At your expense. With no compensation for the months of construction you've already paid for. That's the worst case, and it does happen.
The good news: the answer is usually straightforward. You either fall within permitted development (PD) rights and can build without a formal application, or you don't and need to apply. The answer depends on what you're building, how big it is, what type of property you own, and where it sits. Everything in this guide applies to extensions in England regardless of what the extension is for.
Two Routes, One Question
Every extension in England takes one of two routes.
Route one: permitted development (PD). Your extension falls within a set of nationally defined size and position limits. You don't need to apply for planning permission. You can build, provided you meet every condition. The rules are precise, and misinterpreting them is easy. We cover these in detail in Permitted Development Rules.
Route two: householder planning application. Your extension exceeds the permitted development limits, or your property type or location removes your PD rights entirely. You submit an application to your local planning authority, pay the fee, and wait for a decision. The council assesses your proposal against its impact on neighbours, appearance, parking, and drainage.
| Permitted Development | Householder Planning Application | |
|---|---|---|
| Do you apply to the council? | No (but get a Lawful Development Certificate for proof) | Yes, formal application through the Planning Portal |
| Fee | £274 for a Lawful Development Certificate | £548 (England, from April 2026) |
| Timeline | LDC takes 6-8 weeks | Target 8 weeks, often longer |
| What it controls | Size, height, position, materials, curtilage coverage | Appearance, neighbour impact, parking, drainage, character |
| Building regs still required? | Yes, always | Yes, always |
Whichever route applies, you still need building regulations approval. That's the part most people overlook. Planning permission and building control are completely separate processes run by different departments with different fees. Planning controls what your extension looks like from the outside. Building control ensures it won't fall down, catch fire, or leak heat. You need both.
Building control is a separate process with its own application, fees, and inspections. Read Building Control: How to Apply and What to Expect before assuming planning permission is all you need.
When You Definitely Need Planning Permission
Some situations remove any doubt. If any of these apply, you're submitting a planning application.
Listed buildings. Any external alteration to a listed building needs both planning permission and listed building consent. This applies to Grade I, Grade II*, and Grade II listed properties. Even minor external changes that would normally fall under PD require formal consent.
Conservation areas. Permitted development rights are restricted in conservation areas. Side extensions and certain cladding changes are specifically excluded. Rear extensions may still be possible under PD depending on the specific restrictions your council has applied, but check before you assume.
Flats and maisonettes. PD rights for extensions apply only to houses. If you live in a flat or maisonette, you need planning permission for any extension.
Exceeding PD limits. If your single-storey rear extension goes beyond 6 metres (semi-detached or terraced) or 8 metres (detached) under the Larger Home Extension scheme, or exceeds the standard 3/4 metre limits without prior approval, you'll need a full application. The same applies if the extension covers more than 50% of your garden or exceeds 4 metres in height. Any PD condition you fail to meet pushes you into the formal application route.
Previous extensions. Here's where people get caught. The PD limits are measured against the "original house," defined as the house as it stood on 1 July 1948 (or when first built, if later). If a previous owner added a conservatory in 1990, that counts against your allowance. Check your property's planning history with the council before relying on PD.
Article 4 directions. Some councils remove PD rights for specific streets or areas using Article 4 directions. This is separate from conservation area restrictions. Your council's planning department will tell you if one applies to your address.
How to Check
Don't start with Google. Start with your local council's planning portal.
Every local authority in England has a public planning register. Search your address and you'll see every planning application ever submitted for your property, plus any conditions, Article 4 directions, or conservation area designations that apply. This is the definitive source.
Search your address on your local council's planning portal before doing anything else. You'll find your property's planning history, any existing permissions, and whether your area has restrictions that remove PD rights. The national Planning Portal at planningportal.co.uk also has a useful interactive tool for checking PD limits.
If you're unsure after checking, pay for a pre-application advice service. Most councils charge £100–300, though London and larger urban councils can charge £400–600 for written advice. You describe your proposal, and a planning officer gives you an informal opinion on whether it needs permission and whether it's likely to be approved. Not binding, but useful. It's cheaper than submitting a full application only to have it refused.
Your architect should also confirm the planning route as part of their initial consultation. Any competent architect will assess PD limits and advise whether you need to apply. If your architect doesn't raise this in the first meeting, ask directly.
What the Council Actually Assesses
Planning permission is not about whether your extension is structurally safe (that's building control). The council is assessing something different entirely.
Neighbour impact comes first. Will the extension overshadow their garden or block light to neighbouring windows? Will it overlook a private space? Then there's appearance: does the extension respect the character of the street, and are the materials appropriate? The council also weighs practical constraints like parking capacity and drainage.
The council will consult your neighbours as part of the process. Neighbours can object, and if they do, the planning officer considers those objections alongside their own assessment. Objections don't automatically mean refusal, but they do mean the officer has to address the concerns in their decision report.
Planning officers routinely visit while the homeowner is out. They inspect from the outside, take notes, and leave without making contact. Don't rely on a site visit as a chance to explain your proposal. Your drawings need to communicate everything.
What It Costs
The council fee alone for a householder planning application is £548 (as of April 2026). But the total cost is higher once you include architect submission fees, OS maps, and the Planning Portal service charge.
Total planning application cost (England)
| Householder planning application fee (England) | £548 |
| Architect planning submission fee | £100 – £200 |
| OS maps for a planning application | £10 – £40 |
| Planning Portal online service charge | £84 |
| Total | £742 – £872 |
Prices as of April 2026
Price review due: Planning Portal online service charge
How Long It Takes
The statutory target is 8 weeks from validation to decision. Budget for 8-12 weeks in practice. Once granted, planning permission is valid for 3 years - miss that window and you reapply from scratch.
Read the Conditions
Planning permission rarely arrives without conditions attached, and every one is legally enforceable. Some must be formally discharged before you can start work on site - miss one and the entire permission can be invalidated.
If Your Application Is Refused
Refusal isn't the end. You can appeal to the Planning Inspectorate (free, within 12 weeks) or resubmit an amended application addressing the reasons for refusal.
For the full application process - every cost broken down line by line, timeline and what to do if the council is slow, how to discharge conditions, and what to do if refused - read Submitting a Planning Application.
Planning Permission vs Building Control: Know the Difference
This is the single most common misunderstanding. Planning permission granted does not mean you can start building. It means the council is satisfied that your extension is acceptable in terms of appearance, impact, and land use. It says nothing about whether the structure is safe, energy-efficient, or compliant with fire regulations.
Building control is a completely separate application with its own fee (typically £250–550 for the application plus £330–400 for inspection fees, varying by council and floor area), its own documents (structural calculations, thermal calculations, drainage plans), and its own inspections throughout the build. Your architect prepares the building control submission separately from the planning application.
You need both. Always. Even if your extension falls under permitted development and doesn't need planning permission, you still need building regulations approval.
Planning Permission Checklist
Covers everything to check before submitting: PD limits, conservation area status, Article 4 directions, neighbour considerations, parking, and what to prepare for your architect.
Do You Need Planning Permission?
Answer a few questions about your property and proposed extension to find out whether you need planning permission, can use permitted development, or may qualify for prior approval.
What to Do Next
If you've established that your extension falls within permitted development, head to Permitted Development Rules for the specific size and position limits. Get a Lawful Development Certificate (£274) as formal proof. You still need building control approval and potentially a party wall agreement before you can start building.
If you need planning permission, the process starts with your architect. They prepare the drawings, submit the application, and manage the council interaction. Read Finding an Architect to understand what that relationship costs and how to appoint one.
Either way, don't confuse planning with building control. They run in parallel but answer different questions, cost different amounts, and involve different people. Getting planning permission is the first gate. Building regulations approval, party wall clearance, and finding a builder all come next.