You have sketched an extension on the back of an envelope, asked a neighbour for advice, and now nobody agrees.
Some say you need full planning permission. Others say it falls under permitted development.
Sorting out planning permission for an extension in Kent is rarely as simple as a quick chat over the fence. The rules vary by council, by location, and by the size of what you want to build.
This guide explains, in plain English, when you need planning permission, what permitted development covers, how the process works, what it costs, and how to avoid the mistakes that cause refusals.
Do You Need Planning Permission for an Extension in Kent?
Whether you need planning permission for an extension in Kent depends on the size, height, and location of the build. Many smaller extensions fall under permitted development and need no application. Listed buildings, conservation areas, and properties in Areas of Outstanding Natural Beauty almost always need full planning permission. Always check with your local Kent council before starting work.
Kent is split across 12 local planning authorities. Each one applies the national rules, but local context matters.
For example, Tunbridge Wells and Sevenoaks sit largely within the High Weald and Kent Downs Areas of Outstanding Natural Beauty, where permitted development rights are restricted.
Coastal authorities like Thanet and Dover have their own conservation considerations. Maidstone, Canterbury and Tonbridge & Malling each handle the same rules with different local nuance.
What Is Permitted Development (and What Does It Cover in Kent)?
Permitted development is a set of national planning rules that lets you build certain extensions and alterations without applying for full planning permission. It covers most modest single-storey rear extensions, side extensions, and loft conversions, as long as they meet strict size, height, and material limits set by the government.
Permitted Development Limits for House Extensions
The main limits to know are these:
- Single-storey rear extensions can extend up to 4 metres from the original rear wall on a detached house, or 3 metres on terraced and semi-detached homes.
- With prior approval, those limits rise to 8 metres for detached homes and 6 metres for others.
- Maximum eaves height is 3 metres if within 2 metres of a boundary, and overall height is capped at 4 metres.
- Side extensions must be single storey, no more than 4 metres high, and no wider than half the original house.
- Materials must be similar in appearance to the existing property.
- No more than half the land around the original house can be covered by extensions and outbuildings.
These rules apply to houses, not flats or maisonettes.
One critical caveat: permitted development does not apply where rights have been removed by an Article 4 direction. These are common in parts of Tunbridge Wells, Canterbury, and other Kent conservation areas.
When You Will Definitely Need Full Planning Permission
You will need full planning permission for an extension in Kent if any of the following apply:
- Your property is a listed building. Any work needs listed building consent on top of planning permission.
- You live in a conservation area, and you want a side extension, large rear extension, or external cladding change.
- You live in an Area of Outstanding Natural Beauty such as the High Weald or Kent Downs.
- Your design exceeds permitted development size or height limits.
- You own a flat or maisonette. Permitted development rights for extensions do not apply.
- Your property has an Article 4 direction in place removing permitted development rights.
If any of these apply, the safe move is to assume you need full planning permission and budget for the application.
Planning Permission vs. Building Regulations: What Is the Difference?
Planning permission and building regulations are two completely separate processes, and confusing them is one of the most common mistakes Kent homeowners make.
Planning permission controls what you build. Building regulations control how you build it.
Even if your extension falls under permitted development and skips planning, you almost always still need building regulations approval. They are issued by different teams and assessed against different rules.
| Factor | Planning Permission | Building Regulations |
|---|---|---|
| What it controls | Size, location, design and appearance | Structural safety, insulation, fire safety |
| Who issues it | Your local council planning team | Building control body or approved inspector |
| When you need it | Only if outside permitted development | Almost always for an extension |
| Penalty for ignoring | Enforcement notice; may force demolition | Fines and unsellable property |
In short: planning is about whether the council accepts your design. Building control is about whether the build is structurally safe and properly insulated. You need to clear both.
How to Apply for Planning Permission in Kent (Step-by-Step)
If your project needs full planning permission, here is the process from start to finish.
- Identify your local planning authority. Kent has 12, including Maidstone, Canterbury, Tunbridge Wells, Sevenoaks, Ashford, and Dartford. Check which one covers your postcode.
- Get architectural drawings prepared. You will need scaled site plans, existing and proposed elevations, and floor plans. We work hand-in-hand with reliable Kent architects and can introduce you to the right partner.
- Submit your application through the Planning Portal or directly via your council’s online system.
- Pay the householder application fee. Verify the current fee on GOV.UK before you submit, as fees are reviewed periodically.
- Wait through the public consultation period. Neighbours and statutory consultees have 21 days to comment on your plans.
- Receive a decision, usually within 8 weeks for householder applications. The council will either approve, approve with conditions, or refuse.
Pro tip: paying for pre-application advice from your council adds 4 to 6 weeks but cuts refusal risk significantly. We almost always recommend it for borderline cases.
How Much Does Planning Permission Cost in Kent?
Most homeowners only budget for the council fee and get a nasty surprise. The headline application fee is just one line on the bill.
Here is what you should actually budget for:
- Householder planning application fee paid to the council. Verify the current figure on GOV.UK before applying.
- Architect drawings and design fees. These vary widely depending on project scale and the architect’s experience.
- Planning consultant fees if your application is complex, in a conservation area, or involves a listed building.
- Structural engineer reports for double-storey extensions or loft conversions.
- Building regulations application fees, which are paid separately from planning.
If your application is refused and you have to resubmit or appeal, the timeline doubles and costs climb fast. Getting the design right first time is the cheapest path.
How Long Does Planning Permission Take in Kent?
Standard householder planning applications in Kent are decided within 8 weeks. That is the statutory target your council works to.
More complex cases take longer. Listed building consent, conservation area applications, and proposals needing amendments often run to 12 weeks or more.
Once granted, your planning permission is valid for 3 years. You must start work within that window or the permission lapses.
Common Reasons Kent Planning Applications Get Refused
From our work guiding Kent homeowners from first drawing to final finish, we see the same reasons for refusal again and again.
- Overdevelopment of the plot. The extension is too large compared to the original house or garden.
- Loss of light or privacy to neighbouring properties. This is the most common neighbour objection.
- Out-of-character design. A glass and steel extension on a Tudor cottage in a conservation area will not pass.
- Inadequate parking. Some Kent councils require off-street parking provision to be retained.
- Highways objections, especially on busy roads or near junctions.
- Tree preservation orders. Removing or working near a protected tree without consent is a serious issue.
Most of these are avoidable with the right design and the right early conversations. A pre-application chat with the council and a knowledgeable architect prevents the majority of these problems.
Should You Apply for a Lawful Development Certificate?
A lawful development certificate, or LDC, is a formal council document confirming that your work is lawful under permitted development rules. It is not the same as planning permission, but it provides legal proof that you did not need any.
Even when you are confident your extension falls under permitted development, applying for an LDC is smart. It protects you when you sell the property, because conveyancers and buyers will ask for proof.
The application process is simpler than full planning, the fee is lower, and the certificate gives you peace of mind. We recommend it to most Kent homeowners building under permitted development.
Frequently Asked Questions
Do I need planning permission for a small rear extension in Kent?
Not always. Small single-storey rear extensions often fall under permitted development. Detached homes can extend up to 4 metres, others up to 3 metres, as long as height and boundary rules are met. Conservation areas and listed buildings are different and usually require a full application.
Can my neighbour stop my Kent extension?
Neighbours cannot block an extension on their own. They can submit objections during the consultation period, and the council will weigh them against planning policy. Common valid concerns are loss of light, loss of privacy, and noise. Personal disputes carry no weight in the decision.
What happens if I build an extension without planning permission?
The council can issue an enforcement notice requiring you to alter or demolish the work. Selling the property becomes very difficult without a certificate of lawfulness or retrospective permission. Always check before you build, even for small projects.
Do I need planning permission for an extension in a Kent conservation area?
Usually, yes. Permitted development rights are restricted in conservation areas, especially for side extensions, larger rear extensions, and external alterations. Many parts of Canterbury, Tunbridge Wells, and Sevenoaks fall into this category. Always confirm with your local council before starting.
Final Thoughts
Most Kent extensions either fall under permitted development or need full planning permission. The line between the two depends on size, location, and whether your property sits in a protected area.
The biggest mistake we see is homeowners assuming what their neighbour did applies to them. It rarely does. A property two streets away can have completely different rules because of an Article 4 direction or a conservation area boundary.
At BDC Construction, we work hand-in-hand with trusted Kent architects and guide homeowners from the very first drawing through to the final finish. That includes helping you understand whether your project needs planning permission or falls under permitted development.
If you would like a plain-English chat about your extension idea, get in touch with our team.