Can I Build An Extension Without Planning Permission?

Permitted development rights are great news for homeowners; they allow for certain kinds of extensions to be added to your house, without having to go through the Planning Permission process. Which isn’t to say that there aren’t regulations, standards, and criteria to meet; extensions need to be a certain size, and there are rules about their outward appearance.

The My Build My Way team is always keen to make home improvements easier to manage, so we’ve created a guide which tells you what extensions permitted development rights allow. Even if you find you can build without seeking planning permission, you will need to submit documents to your local planning department for their sign off – so we take you through these as well.

Loft Conversions

Most loft conversions will come under permitted development rights. There are, however, exceptions, so you will need to check the rules below to see whether or not you need planning permission to proceed:

  • Extensions that go beyond the slope of the roof on the side facing the highway are allowed, and rooflights are generally acceptable in such cases.
  • The total increase in roof volume cannot exceed 50 cubic metres for a detached or semi-detached house, or 40 cubic metres if you have a terrace house. Dormers should be set back a minimum of 20cm from the eaves.
  • You are not permitted to extend the construction above the highest point of the existing roof.
  • Windows on the side of the house must be glazed to ensure privacy. If these windows can be opened, the lower edge of the opening section must be at least 1.7 meters above the floor.
  • The access staircase should have at least 2 metres head height clearance.
  • Expansions should not protrude beyond the outer face of the original house wall. Verandas, balconies, and raised platforms are not allowed.
  • Materials similar in appearance to the original house should be used.
Rear Extensions

A rear extension refers to a type of architectural addition that extends the existing structure beyond its original rear boundary, typically to create additional living space or enhance the functionality of the property. In this case the term refers to a single storey extension. The rules governing permitted development rights for rear extensions are as follows:

  • Single storey rear extensions can extend out by up to 3 metres for semi-detached, terraced and link-detached houses (if the garages share a wall), and by 4 metres for a detached house. These dimensions are based on the original plans of the building, or as of 1 July 1948 if the property is older.
  • The extension should not exceed a height of 4 metres. Any part of the roof that is within 2 metres of a neighbour’s boundary should not exceed 3 metres.
  • Rear extensions should not extend beyond the side of the house, and they are not allowed to cover more than half the land surrounding the original property. It must not come within 7 metres of the rear property boundary.
  • The materials used should be in keeping with the original house.
Side Extensions

A side extension is an excellent option if you have land at the side of your house and you don’t want to reduce the size of your garden. Adding a room to the side of your property often works well with your home’s layout and provides a use for space that otherwise would lie dormant. Here are the rules for side extensions under permitted development tights:

  • The extension should not exceed half the width of the original property.
  • The side extension can project into the back garden beyond the back of the house by up to 3 metres for semi-detached, terraced, or link-detached houses, or 4 metres for detached houses. This is based on the original building plans or the state of the house as of July 1, 1948, if it is an old property.
  • The maximum height allowed for the highest point of the roof is 4 meters. If any part of the roof is within 2 metres of your neighbours’ boundaries, it must not exceed a height of 3 metres.
  • You are allowed to build right up to the boundary with your neighbour’s property, but an early discussion about this could save issues further down the line.
  • Permitted development rights do not allow for full width wrap around extensions. However, a partial wrap around extension is permitted as long as the total width at its widest point does not exceed half the width of the original building.
  • The materials used in the extension should be similar to those of the original property.
2-Storey Extensions

A 2-storey extension is a great option if you’re wanting to add an extra bedroom or bathroom to the upstairs of your home, whilst extending your kitchen or living space down below. These are allowed under permitted development rights, so long as they fulfil the following rules:

  • 2-storey extensions can only be built at the rear of your property.
  • Semi-detached, terrace, or link-detached houses can extend up to 3 metres from the rear elevation, while detached houses can extend up to 4 metres.
  • The height of the roof ridge and eaves should not surpass the height of the original house. If any part of the roof is within 2 metres of your neighbours’ boundaries, its maximum height must be 3 metres.
  • The extension must not cover more 50% of the land surrounding the property.
  • The roof pitch should match the style of the existing roof, and the tiles and external materials should be consistent. The pitch of the new roof should also align with that of the original house. For any second-storey windows, they must have obscured glass and their opening parts should be at least 1.7 meters above the floor.

What Documents Are Needed With Permitted Development Rights?

Whilst much of the onerous paperwork involved in planning permission is removed by the use of permitted development rights, you will still need to let your local planning department see plans for the build that demonstrate the exact dimensions and positioning of your extension. You will also need to submit the following:

  • Party Wall Agreements – this applies only if your property is not detached.
  • Building Regulations Certificate – this applies to all extensions.
  • Right to Light Report – this is generated by a surveyor, and is necessary if your neighbours are concerned about losing light as a result of your build.
  • Build Over Agreement – if you are building over, or near sewer pipes, your local water authority will need to agree to it.

Permitted development rights are finite. If your building has already been extended in its history, the rights may have been used up. A second extension can be added but the total size all the property’s extensions (since 1st July 1948) must not exceed the present limits.


Looking to Add an Extension to Your Home?

My Build My Way is here to help. As a build and design business, we connect clients with reputable local builders or architects who offer excellent support at competitive prices.

If you already have extension plans drawn up, we’ll provide quotes from verified local builders who would be a good fit for your project. We work with leading UK contractors to ensure that the introductions we make are appropriate to the type of build, and our client’s timeframe.

Our goal is to help you find the right contractor at the right price, ensuring top-quality workmanship. Once you make your choice, we arrange for a building inspector to ensure quality checks at each stage.

If you’re planning an extension, contact us at 0333 772 2356 or send us a message. Learn more about our process at