Do all extensions need planning permission?
No. Some extensions may be possible without a full planning application, depending on the property and proposal.
Do I Need Planning Permission For An Extension?
One of the most common questions homeowners ask is whether an extension needs planning permission. The answer depends on the size, location and design of the extension, as well as the property itself. Some extensions may be possible without a full planning application, while others require formal approval.
Try it on my houseThe 10-second answer
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 a broader overview of the two routes, read our guide to planning permission vs permitted development.
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.
- Rear extensions — often the most common type; depth and height are key checks.
- Side extensions — width, height and visibility from the street can be important.
- Front extensions — usually more visible and often face stricter scrutiny.
- 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.
Common types of extension
The type of extension affects what is typically checked. These summaries are general — the outcome still depends on your property and design.
Rear extension
What it is: An extension built at the back of the house, often into the garden.
Typical considerations: Depth, height, distance to boundaries and impact on neighbours.
Why answers vary: A modest single-storey rear extension may fall within permitted development limits on some houses, while a larger or two-storey design may need planning permission.
Side extension
What it is: An extension along the side of the house, often between the house and a boundary.
Typical considerations: Width, height, how visible it is from the street and effect on neighbour amenity.
Why answers vary: Side extensions can be harder to fit within permitted development limits, especially on narrower plots.
Front extension
What it is: An extension at the front of the property, often a porch or projection toward the street.
Typical considerations: Visibility, highway access and effect on the character of the area.
Why answers vary: Front extensions are often more restricted and may need planning permission even when modest.
Wraparound extension
What it is: An extension that wraps around a side and rear corner of the house.
Typical considerations: Combined footprint, overall scale and impact on the garden and neighbours.
Why answers vary: Larger combined areas are more likely to exceed permitted development allowances.
Two-storey extension
What it is: An extension with ground and first-floor accommodation.
Typical considerations: Height, massing, overlooking and relationship to the existing house.
Why answers vary: Two-storey proposals often face tighter limits and may be more likely to need planning permission.
Single-storey extension
What it is: A ground-floor-only extension, such as a kitchen or living room expansion.
Typical considerations: Depth, height and how much of the garden is covered.
Why answers vary: Some single-storey rear extensions may be permitted development in the right circumstances, but restrictions on the property can rule this out.
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.
Single-storey rear extension
A homeowner wants to extend the kitchen into the rear garden. Key checks usually include how deep the extension would be, how high it would be, how close it sits to the boundary, whether the house already has a rear extension, and whether the property is in a conservation area or subject to an Article 4 direction (a local restriction that can remove some permitted development rights).
A modest design on a typical house with no special restrictions may sometimes fall within permitted development limits, but the exact measurements and property history must be checked.
Two-storey rear extension
A two-storey rear extension adds more volume and height than a single-storey design. Planning considerations often include overlooking of neighbours, the scale of the extension relative to the existing house, and whether permitted development allowances for two-storey rear extensions are met.
Because two-storey proposals are usually more prominent, they are more likely to need planning permission — but the answer still depends on the specific property, design and location.
Front extension
A front extension or porch is usually more visible from the street. Checks often focus on how the design affects the character of the property and the area, highway access and whether the proposal sits within any permitted development limits for front projections.
Front extensions can be more restricted than rear extensions. Even a relatively small design may need planning permission depending on the property and local context.
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 — areas where the character of the place is protected; permitted development rights may be more limited.
- Listed buildings — properties of special architectural or historic interest; 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.
Try it on my house