Do I need planning permission for an extension?

The thought of extending your home is an exciting prospect, but before you start choosing paint colours and finishes, you must first find out what planning permission you will need.

If you start your build without the necessary planning permission, you could face an enforcement notice. In a worst-case scenario, this can result in you having to take the whole building down.

Planning permission is not needed for every extension, but it’s important to check the rules before you start your build to save potential upheaval further down the line.

To make things simple, we’ve outlined the planning permission requirements for some of the most popular extensions, including:

• Single-storey extensions
• Two-storey extensions
• Kitchen extensions
• Garage extensions

We’ll also explain when you don’t need permission and what the cost of planning permission for an extension is, to help you budget for this part of the project.

Planning permission for an extension

If you build within your permitted development rights, you don’t need planning permission.

Permitted development rights allow a homeowner to make alterations to their property quickly, without having to apply for planning permission. However, within permitted development, you must make sure that specific limitations and conditions are met.

Our permitted development rights guide will take you through the updated Government legislation, as of September 2020. This clearly explains what permissions are granted for different types of property, and the restrictions to be aware of.

For any sort of extension, we recommend you contact your local planning authority (LPA), to check planning requirements before work begins.

Planning permission for a single-storey extension

You will not need planning permission for a single-storey extension if it falls within permitted development rights, providing certain limitations and conditions are met.

The recently relaxed permitted development rules mean that you can build an extension without planning permission of up to six metres (or eight metres if your house is detached). The extension cannot be more than four metres high. If the extension is within two metres of the property’s boundary, the extension can’t be more than three metres high.

We advise you to speak with a professional, such as an architect or designer, before undertaking any work.

Planning permission for a kitchen extension

The good news is, you do not need planning permission for a kitchen extension, providing you meet the conditions and limitations of permitted development, as outlined above.

Planning permission for a garage extension

You will not need planning permission for a garage providing you stay within certain parameters:

• The garage must not be used as a living space.
• For a freestanding garage, it must be less than 15 m2.
• For an attached garage, the floor must be less than 30 m2. The materials used to build the garage must be non-flammable, and be at least 1m from any property boundaries.

Planning permission for a two-storey extension

There are permitted development rights for a two-storey rear extension to a house, meaning you will not need planning permission. However, you will need to make sure your extension adheres to certain conditions and limitations:

• The eaves and pitch heights must not exceed that of the existing house. If the building is within two metres of a boundary, the maximum height of the eaves is limited to three metres.
• You can extend up to three metres from the original house, but it must be more than seven metres from the rear boundary. An extension, shed or outbuilding should not exceed more than 50% of the total plot.
• The materials should have a similar aesthetic to the original house.
• Verandas or balconies are not allowed without planning permission. If your plans include an upper floor window in a side elevation, it must be obscured glazing and non-opening (unless it’s more than 1.7m from floor level internally).

You will need planning permission for a two-storey extension if it’s to the side or front of the original house. And there are a number of considerations that will determine whether your application is granted or refused. This detail can be found in our post on the cost of a double-storey extension.

Flats and maisonettes do not have permitted development rights. And properties that have undergone a change of use in the past may not have permitted development rights either.

It’s a good idea to instruct an architect for this type of extension. Their expertise will help to ensure your plans make the best use of the space available.

Cost of planning permission for an extension

Your first port of call when planning an extension should be your local planning office. They will be able to tell you:

• Whether you need planning permission for your extension
• The type of planning permission you need
• The cost of your application

Take a look at our guide on the cost of planning permission to see the different types of planning permission (full planning permission, outline planning permission, and householder planning permission), and their costs. The post also outlines the differing costs depending on your location (England, Scotland or Wales).

As a quick guide:

• Full planning permission is £206 (England) and £202 (Wales). This is for alterations/extensions to a single dwelling house or flat.
• Outline planning permission is £426 (England), £460 (Wales), and £401 (Scotland). These costs are per 0.1 hectares of land (up to 2.5 hectares).
• Householder permission is £206 (England), £230 (Wales), and £202 (Scotland). These costs relate to alterations/extensions to a single dwelling house. This permission is not applicable to flats or altering the number of dwellings.

What to do if you have no planning permission for your extension?

If you have no planning permission for your extension, you can apply retrospectively.

Retrospective planning permission is subject to the same criteria as a standard planning application and won’t automatically be granted. Your plans could be refused. If your application is rejected, you will be required to put things back to how they were unless you appeal the decision and it’s overturned. This is done through your local planning authority.

Retrospective planning permission costs are the same as those for advance permission (as outlined above).

FAQs

How can I apply for planning permission for an extension?

To apply for planning permission for an extension, contact your local planning authority (LPA) through your local council.

How much is planning permission for an extension?

The cost depends on where you live and the type of planning permission you’re applying for.

In England, full planning permission costs £206. Outline planning permission is £426 and householder permission is £206. See our post on the cost of planning permission for a full breakdown of costs.

When do you need planning permission for an extension?

Generally, you need planning permission if you want to:

• Build something new
• Make a major change to your building, such as an extension
• Change the use of your building

If your extension falls within permitted development rights, you will not need planning permission.

To be sure, you should always check with your local planning authority (LPA) before you commence any work.

Do you need planning permission for a small extension?

Homeowners are permitted to build an extension of up to six metres without planning permission. For a detached house, the limit is eight metres.

What is lawful development?

Lawful development is development against which no enforcement action may be taken and where no enforcement notice is in force, or, for which planning permission is not required. It’s not a legal requirement to have a lawful development certificate, but it’s worthwhile getting one. It’ll prove to the local authority and any future buyers that your build was legal at the point of construction.