Planning Permissions for Extensions in London

Planning Permissions – these words have struck trepidation into the heart of many a home-owner desirous of extending their property. Are you the same? Don’t worry, this subject isn’t as complex as it may seem. We have put together this article so you can clearly see for yourself whether or not you will need planning permission for your extension project.


Let’s start by considering when you don’t need planning permission.

Planning permissions for extensions in London

Permitted Development Rights

First of all, we’ll answer the question: Do all extensions in London need planning permission? The short answer is: no. This is where something called permitted development rights come into play.

Permitted development rights allow a property-owner to make certain changes to a building without the need to apply for planning permission. It is when you wish to exceed these rights that you need to apply for planning permission. The majority of the restrictions that keep you under your permitted development rights are for work done near a boundary, next to a road or at the front of the house. 

Let’s take a look at some of the changes that would necessitate planning permission.

Planning Permission

The point at which you need to apply for planning permission can vary depending on the type of extension. Let us begin by considering the crossing point for all extensions in London then we can see the added restrictions for side extensions and rear extensions (both for single-storey and two-storey buildings). 

Please note, in the information below, when talking about ‘the original house’ we are referring to the house as it was originally built or as it stood on 1 July 1948, if it was built before that date. You need to bear in mind whether a previous owner of the property has previously built an extension to the house because the changes made are not considered part of ‘the original house’.

All extensions in London

You need planning permission:

  • if you cover more than half of the land around the ‘original house’ with extensions (or other buildings for that matter)
  • to extend a section of your building facing a motorway
  • if you build higher than the current height of the property’s roof or the height of eaves and ridges
    • this includes chimneys, microwave antennae, and pipes
  • if the height of the eaves exceeds 3 metres and is within 2 metres of the nearest boundary (the edge of the enclosed space surrounding the house. E.g. a wall, a fence or  the wall of an adjacent building
  • if you want to use materials that are dissimilar to those of the existing house 
  • for balconies, verandas, raised platforms etc. (Juliet balconies are not always included in this restriction)
  • if the roof pitch is different than that of the existing house 

Side extensions in London

  • if the extension exceeds 4 metres in height
  • if the extension is more than a single storey
  • if the extension is more than half the width of the ‘original house’

Rear Extensions

For single storey

  • if the extension extends beyond the rear wall of the ‘original house’ by more than 6 metres (or 8 metres for a detached house)
  • if the extension is more than 4 metres in height 

For two-storey

  • if your two-storey build extends beyond the rear wall of the ‘original house’ by more than 3 metres or is within seven metres of any boundary opposite the rear wall of the house
  • if any upper floor windows in a side elevation are obscure-glazed and non-opening (unless it’s more than 1.7 metres above the floor of the room in which it is installed)

Please note: even if you remain within your permitted development rights, you may still need to apply for planning permission if your property is a listed building, a designated area (a conservation area, an Area of Outstanding Natural Beauty, a National Park or a World Heritage Site) or if your local planning authority restricts the permitted development rights for your property.

Restrictive Covenants

Prior to selling you the house, the previous owner may have attached a restrictive covenant to your property as a condition of sale. This can restrict any extension or building work done on your house. Your solicitor had a duty to inform you of this when you bought the property. If you have any doubts, contact your solicitor to make sure no previous covenants were placed on your house.

Building Regulation Standards

Building regulation standards are the specific standards building projects are required to meet to be approved. These regulations are put in place to ensure the safety of the build. Most extension projects require approval under the building regulation standards. 

Some work, such as the following, will most likely need building regulation approval. There may be other works not listed here that would require approval.

  • replace windows and doors
  • replace fuse boxes and connected electrics
  • change electrics near a bath or shower
  • install a bathroom that will involve plumbing
  • change roof coverings on pitched and/or flat roofs
  • install or replace a heating system
  • add extra radiators to a heating system

You do not need to apply for approval yourself if the work is carried out by someone who’s registered with a ‘competent person scheme’.

It is crucial for your extension to receive approval in compliance with building regulation standards because your local authority could make you pay for faulty work to be fixed and without approval, you won’t have the certificates of compliance you may need if you wish to sell your home in the future.

For more information on building regulation standards, visit to read their ‘Approved Documents’ on ways to meet building regulations.

Hopefully, this article has clarified the subject of planning permissions for extensions in London, along with permitted development rights and building regulation standards. All in all, we’re sure you’d be happy to know that there are builders that offer turnkey services that handle the entire process of the planning and building, including submitting the right forms to your local council and planning departments.

Information in this article is based on the information published on and Please take into account that this article is not a source of legal information. Consult your local planning office for information pertaining to your specific property before starting your build.