Rear Extension Planning Permission | Do I Need Permission?

The 10-second answer

Do all rear extensions need planning permission?

No. Some modest single-storey rear extensions may fall within permitted development limits on houses with no special restrictions.

What matters most?

Depth, height, number of storeys, distance to boundaries and whether permitted development allowances have already been used.

Does England differ from Scotland?

Yes. Permitted development measurements and rules are not identical north and south of the border.

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 project is relatively modest in scale.
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 project is larger or more prominent.
The property is listed or in a conservation area.
The property is subject to an Article 4 direction or other local restriction.
The proposal exceeds permitted development limits.

Many projects require planning permission, but the answer depends on the individual circumstances.

For wider context on extensions, see our extension planning permission overview. For the two planning routes, planning permission vs permitted development. For costs, extension costs.

What affects whether a rear extension needs planning permission?

A rear extension builds into the garden behind the house. In planning terms, the key question is whether the proposal fits within permitted development (national rules that may allow certain works without a full planning application) or needs formal planning permission from the local planning authority (your council's planning department).

Common factors include:

Extension depth — how far the extension projects beyond the rear wall
Extension height — eaves and ridge height relative to the existing house
Number of storeys — single-storey and two-storey rear extensions are assessed differently
Distance from boundaries — how close the extension sits to garden boundaries
Previous extensions — earlier rear or side additions may have used permitted development allowances
Property restrictions — conservation areas, listed buildings, Article 4 directions and flats all change the answer

For cost planning alongside permissions, see our extension costs guide. For how planning differs from building standards, see building regulations vs planning permission or building warrant vs planning permission in Scotland.

England and Scotland: why rear extension rules differ

Planning Digital covers England and Scotland. Both countries allow some rear extensions under permitted development, but the detailed limits — including how depth is measured and what counts toward allowances — are not identical.

Local planning policies can also differ. A design that might be acceptable under permitted development in one area may need planning permission in another because of property-specific restrictions. Read more in our guides to planning permission in England and planning permission in Scotland.

Factors that can change the answer

Even when a rear extension sounds modest, the following can remove permitted development rights or require planning permission:

Conservation areas — permitted development rights may be more limited; see conservation areas explained
Listed buildings — most extension work needs listed building consent; see listed building consent explained
Flats and maisonettes — generally have more limited permitted development rights than houses
Previous extensions — may have used up permitted development allowances
Article 4 directions — local restrictions that can remove some permitted development rights
Two-storey designs — often face tighter limits than single-storey rear extensions

Typical homeowner examples

These examples illustrate common situations. They are not formal determinations and do not guarantee an outcome.

Modest single-storey rear kitchen extension

A homeowner wants to extend the kitchen by a few metres into the rear garden. Checks usually include depth, eaves height, whether the house already has a rear extension, and whether the property is in a conservation area.

On a typical detached or semi-detached house with no special restrictions, a modest design may sometimes fall within permitted development limits — but exact measurements must be checked.

Two-storey rear extension

Adding a ground-floor living space and a bedroom above increases volume and height. Overlooking of neighbours and the scale of the extension relative to the existing house become important.

Two-storey rear extensions are more likely to need planning permission, though permitted development may still apply in some cases if limits are met.

Rear extension on a terraced house

Terraced properties often have smaller gardens and closer neighbours. Depth limits may be tighter, and the extension's impact on neighbour amenity (quality of life for nearby residents) can matter more if planning permission is required.

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.
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. Measurements, previous additions and neighbour impact all matter.
Remember that planning permission and building regulations or a building warrant are separate. You may need both. See our guide to building regulations vs planning permission or building warrant vs planning permission.

Planning Digital helps bring these checks together so you can understand the likely planning route before going further.

Common mistakes

Assuming a neighbour's project means yours is allowed — each property is assessed on its own facts.
Ignoring previous additions that may have used permitted development allowances.
Confusing planning permission with building regulations or a building warrant — see building regulations vs planning permission.
Relying on generic online advice without checking address-specific restrictions.
Committing to builders or suppliers before understanding planning constraints on the site.
Measuring depth from the wrong point on the house — permitted development uses specific reference points.

Frequently asked questions

Do I always need planning permission for a rear extension?

No. Some rear extensions may be permitted development if your property retains those rights and your proposal meets the rules. See permitted development explained for how those rights work.

How deep can a rear extension be without planning permission?

It depends on the property, country and whether the extension is single or two storeys. There is no one depth that applies to every house — check your specific proposal.

Does a conservatory at the rear need planning permission?

Conservatories are often assessed similarly to extensions for planning purposes. Size, height and position determine whether permitted development might apply.

Can I extend further if my neighbour has?

No. Each property is assessed independently. Your neighbour's extension does not create rights on your land.

Do I need a lawful development certificate?

If you believe your rear extension is permitted development, you can apply for a lawful development certificate for formal confirmation. See lawful development certificate explained.

How can I check my own rear extension?

Start with your address, property type and the depth and height of your design. Planning Digital's Project Planner can help identify constraints and the likely route. You can also compare with side extension planning permission and front extension planning permission if your project wraps around the house.

Check your own rear extension

Depth, height and property restrictions all affect the answer. Planning Digital helps homeowners understand the likely planning route before going further.

Try it on my house

Do I Need Planning Permission For A Rear Extension?