Do all extensions need planning permission?
No. Some extensions may be possible without a full planning application, depending on the property and proposal.
Extension Planning Permission: An Overview
This guide is an overview of extension planning permission. Whether you need approval depends on extension type, size, location and property restrictions. For detailed guidance on a specific design, use the extension type guides below.
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What determines the answer?
Factors such as size, height, position, previous extensions, property type and local restrictions.
Does England differ from Scotland?
Yes. Permitted development rules are not identical and should be checked based on location.
Do I still need building regulations or a building warrant?
Possibly yes. Planning permission and building standards approval are separate processes.
Which route might apply?
You may be looking at permitted development if:
- The extension is relatively modest.
- The property is a house rather than a flat.
- There are no special restrictions affecting the property.
- The proposal falls within permitted development limits.
This does not automatically mean permitted development applies. Every property and proposal is different and still needs to be checked.
You may need planning permission if:
- The extension is larger or more complex.
- The property is listed.
- The property is in a conservation area or subject to restrictions.
- The proposal exceeds permitted development limits.
Many extensions require planning permission, but the answer depends on the individual circumstances.
For the two planning routes, read our guide to planning permission vs permitted development. For budget planning, see extension costs.
What factors affect whether an extension needs planning permission?
There is no single yes-or-no answer for all extensions. Homeowners usually need to consider how the proposal fits the property and the rules that apply to that address. Common factors include:
- Extension size — larger extensions are more likely to need planning permission or to exceed permitted development limits.
- Extension height — height relative to the existing house and neighbouring properties can matter.
- Distance from boundaries — how close the extension sits to garden boundaries or neighbouring homes.
- Number of storeys — single-storey and two-storey extensions are assessed differently.
- Extension type — rear, side, front and garage conversion extensions are checked differently.
- Existing additions to the property — previous extensions may have used up permitted development allowances.
- Plot constraints — such as access, trees, flood risk or awkward site shape.
Permitted development (national rules that may allow certain works without a full planning application) is only one part of the picture. Property-specific restrictions can change the answer entirely.
Extension types: detailed guides
Use these guides for depth on a specific extension type — each covers permitted development limits, typical examples and property checks for that design.
Rear extension
The most common type. Depth, height and storeys are the main checks.
Side extension
Often tighter on narrow plots. Width and street visibility matter.
Front extension
Usually more visible. Porches and front projections face stricter limits.
Garage conversion
Change of use from parking to living space. External alterations can affect the route.
Wraparound and two-storey extensions combine checks from more than one elevation — see the rear and side guides. For budget planning, see extension costs.
England and Scotland: Why the answer can differ
Planning Digital covers England and Scotland. Although both countries use the concepts of planning permission and permitted development, the detailed rules are not identical.
Permitted development rights for extensions — including size limits and how they are measured — can differ between England and Scotland. Local planning policies and constraints also vary by council.
The same extension design might face different limits north and south of the border, or different local tests if planning permission is required. Always check the specific property address and country before assuming an extension is allowed without a planning application.
Typical homeowner examples
These examples illustrate how homeowners often think about extensions. They are not formal determinations and do not guarantee an outcome.
For type-specific examples, see rear, side and front extension guides. These overview examples cover combined designs.
Wraparound extension
A wraparound design combines side and rear additions. The combined footprint is assessed against permitted development allowances — see the rear and side guides for the checks on each elevation.
Two-storey extension
A two-storey extension adds volume and height on two floors. Overlooking and scale relative to the existing house are important — often across more than one elevation.
Garage conversion to living space
Converting an integral garage may be permitted development with minimal external changes — see the garage conversion guide for detail.
Factors that can change the answer
Even when an extension type is often discussed as permitted development, the following can remove rights or require planning permission:
- Conservation areas — see conservation areas explained; permitted development rights may be more limited.
- Listed buildings — see listed building consent explained; most extension work needs listed building consent and often planning permission.
- Flats and maisonettes — generally have more limited permitted development rights than houses.
- Previous extensions — earlier additions may have used up permitted development allowances.
- Article 4 directions — local restrictions that can remove some permitted development rights on certain properties.
- Local restrictions — including planning conditions on the property or area-specific policies.
- Property type — detached, semi-detached and terraced houses can face different practical constraints even under similar rules.
How to check your property
Before relying on general guidance, check the property and proposal together.
- Confirm the property type. Houses, flats and maisonettes are often treated differently for permitted development.
- Check whether the building is listed. Listed building consent and planning permission may both be needed for extension work.
- Check whether the property is in a conservation area or other restricted area. Local restrictions such as Article 4 directions can remove some permitted development rights.
- Review the size, position and design of the proposal. For extensions, consider depth, height, storeys and any previous additions that may have used allowances.
- Remember that planning permission and building regulations or a building warrant are separate. You may need both before work can lawfully proceed.
Planning Digital helps bring these checks together so you can understand the likely planning route before going further.
Common mistakes
- Assuming a neighbour's extension means yours is allowed — each property and proposal is assessed on its own facts.
- Ignoring previous additions to the property that may have used permitted development allowances.
- Confusing planning permission with building regulations or a building warrant (Scotland's building standards approval process) — you may need both.
- Assuming online examples apply to every property without checking address-specific restrictions.
- Starting design work or committing to builders before understanding planning restrictions on the site.
Frequently asked questions
Do I always need planning permission for an extension?
No. Some extensions may be possible under permitted development if your property retains those rights and your proposal meets the rules. Other extensions need planning permission because of size, design, property type or local restrictions.
Can an extension be permitted development?
Sometimes. Permitted development allows certain extensions without a full planning application when national limits are met and the property is not restricted. The extension type, size and location all matter.
Do side extensions need planning permission?
Not always, but side extensions can be harder to fit within permitted development limits. Width, height, visibility and plot width are common factors. Many side extensions require planning permission.
Do front extensions need planning permission?
Often yes, especially for larger or more prominent designs. Small porches may sometimes fall within permitted development limits, but front extensions are usually more restricted than rear extensions.
Does a conservation area affect extensions?
Often yes. Permitted development rights can be more limited in conservation areas, and design quality may be scrutinised more closely if planning permission is required.
Do I still need building regulations or a building warrant?
Very often yes, for structural and safety reasons. In Scotland, a building warrant is the council's approval for building standards. In England and Wales, building regulations approval covers similar requirements. This is separate from planning permission.
How can I check my own extension proposal?
Start with your address, property type, existing constraints and the size and position of your extension. If you want to check your own property and proposal, Planning Digital's Project Planner can help you understand the likely planning route, important constraints and sensible next steps. You can also read our guide to planning permission vs permitted development for wider context.
Check your own extension
The answer depends on the property and proposal. Planning Digital helps homeowners understand the likely planning route, identify important constraints and see what to do next.
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