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Do I always need permission to build an extension?

5th April 2022

The short answer is yes. There are various forms of permission needed if you’re building an extension, and you’ll need to get them, depending on your situation. 

However, some permissions require less effort than others, and if you’re lucky the process can be very simple. And it’s worth keeping in mind that even if the process is not simple, there is plenty of help out there to get you through the process.

To help you make sense of what you might have to deal with, we’ve put together a quick list of the potential permissions you may have to get in order to proceed with your extension. 

Planning Permission

In certain circumstances you can build an extension on your house without planning permission because of something called ‘Permitted Development Rights’. The rules around this are very stringent though, so you’ll have to make sure your project fits within the limitations. Here’s a quick list of what you can do under Permitted Development Rights:

  • You can extend a detached property by 8m to the rear if it’s a single-storey extension (6m for a semi or terraced house), or by 3m if it’s double
  • A single-storey extension can’t be higher than 4m on the ridge and the eaves, and ridge heights of any extension can’t be higher than the existing property
  • Two-storey extensions must not be closer than 7m to the rear boundary
  • Side extensions can only be single storey with a maximum height of 4m and a width no more than half of the original building
  • Any new extension must be built in the same or similar material to the existing dwelling
  • Extensions must not go forward of the building line of the original dwelling
  • In designated areas (such as areas of outstanding natural beauty, conservation areas, etc), side extensions require planning permission and all rear extensions must be single storey
  • An extension must not result in more than half the garden being covered.

This is just a small sample, for the full list visit The Planning Portal.


Three important factors to keep in mind:

  • Is your property a house?
  • Is your property located within a conservation area?
  • Is your property listed?

If your property is within a protected area or it’s listed, your permitted development rights could be restricted, so you’ll need to check the specific rules for your area and property. 

And if your property is a flat or a maisonette, then your property will not fall under permitted development rights and you’ll need to get permission. 

Building Control Approval

Whatever your situation, you’ll always need building control approval before beginning your build. This is usually a relatively simple process and by using a company such as Western Building Consultants you’re less likely to hit any snags.

The point of building control is to ensure that all building projects meet building regulations. 

You have a few options here:

  1. Full plans application. This is potentially the lengthiest process wherein you submit full and detailed plans to your local council. It can take up to eight weeks to go through, although usually within five.
  2. Building notice. This is a simpler option where you or your builder hand in notice that you’re about to start building work to the council. Although this is a quicker option, there is a chance that the council may ask you to change things as the work progresses, or even to demolish work that doesn’t meet regulations. If you go this route it can be very helpful to have an architect on board to ensure your plans are thorough and meet regulations. 
  3. You can also appoint a private approved inspector to verify and check your building plans and work instead of the council. This is a great way to ensure your work goes as smoothly as possible. 

Party Wall Notice  

Under certain circumstances you may find that you also need a party wall notice. This is when your planned extension includes work to a wall that you share with a neighbour, or if your work is within a certain distance and position in relation to a neighbour’s wall.

In general, you have to give notice to your neighbour if you plan to:

  • build on or at the boundary of your two properties
  • work on an existing party wall or party structure
  • dig below and near to the foundation level of their property

You’ll also need to give your neighbour(s) 1-2 months’ notice of this before you plan to start your work. 

You can find out more about Party Wall Notices on the government website

What next?

Do you need help with planning permission, building notices or party wall notices? Get in contact with us at Western Building Consultants and one of our experts will be on hand to offer the services you need. 


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