Do you need planning permission for an extension?


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Do you need planning permission for an extension?

Getting planning permission for an extension is not as complicated and daunting as it might first appear. With permitted development rights, there's a lot of improvement and development work you can do to your home without the need for approval from the planning office.

Do I need planning permission?

If you're thinking about planning permission, you will also need to consider building regulation standards. As with planning, there are guidelines for what can be done without the need to apply for approval.

At Everest, we have an expert team that manages planning permission for you and we've created a guide for what you can and can't do when building an extension.

This guide has been updated to include the new Building Regulations Part O and Part F 2022.

Do you need planning permission for an extension? (Updated for 2023)

The short answer is that you DON'T need planning permission for an extension if you build within your permitted development rights.

Most of the restrictions that don't fall under permitted development are for work to the front of a house, next to a road or near a boundary.

You DO need planning permission for an extension if:

Planning permission for an extension

All extensions:

  • More than half the land around the 'original house' is to be covered (this includes any other buildings)
  • The extension is forward of the front or side of the 'original house' that faces onto a highway
  • Materials used are not similar to the existing house (not applicable for conservatories)
  1. Higher than the highest point of the roof
  2. The eaves and ridge height are higher than the existing house (single-storey and two-storey)
  3. The eaves height is more than 3 metres, if within 2 metres of the boundary.
  4. Addition of verandas, balconies or raised platforms

Side extension planning permission

Side extensions:

  1. More than single-storey or over 4 metres
  2. Wider than half the width of the 'original house'

Building regulation approval is required on any work.

You MAY need permission if you live in a listed building, designated area or fall under an Article 4 Direction.

Is planning permission needed for a single storey extension

Rear extension single-storey:

  1. Extends beyond the rear of the 'original house' by over 6 metres (semi) or 8 metres* (detached house)
  2. More than 4 metres in height

Is planning permission needed for a two storey extension

Rear extension two-storey:

  1. Extends beyond the rear of the 'original house' by over 3 metres or...
  2. within 7 metres of boundary opposite rear wall
  3. Side-facing windows are not obscure-glazed and can open (unless the opening part is 1.7 metres from the floor of the room)
  4. Roof pitch does not match existing house

*If the development is between four and eight metres to the rear of the property, then you must adhere to the neighbour consultation scheme and you have to contact your local planning office.

Conservatories, orangeries and bay windows are all treated as extensions for planning permission purposes:

Do I need planning permission for a conservatory?
Do I need planning permission for an Orangery?
Do I need planning permission for a bay window?

Do you need building regulations for an extension?

When doing development, the building work has to meet specific standards, known as building regulations. The main purpose of the regulations are there for safety purposes and to protect people from potentially dangerous building structures and bad workmanship.

In short, you DO need building regulations approval for an extension.

There are exemptions to building regulations. For example, a conservatory is deemed exempt if it meets the conservatory guidelines (read about planning permission for conservatories here).

Building an extension can be more complicated than a conservatory, so the building regulations must cover all possible variations, such as:

  • Foundations
  • Flooring
  • External walls
  • Internal walls
  • Electrics
  • Doors and windows
  • Drainage
  • Roofs

For more information on building regulations for extensions, we recommend you read these in-depth guidelines here.

Building regulations Part O, reducing overheating in buildings

Prompted by climate change, additions to building regulations came into effect in June 2022.

As part of a drive towards reducing emissions, the regulations are intended to reduce overheating in houses by:

  • Limiting unwanted solar gains in summer
  • Providing adequate means of removing excess heat from a building

Part O relates to glazed areas of new build properties

Windows and glazed areas will be limited to a maximum size depending on:

  • The floor area of the room
  • The direction they face (south, north, east, west)
  • If the building is in a high-risk area (London postcodes being the highest risk)
  • Cross-ventilation inside the building (opening windows on opposite facing walls).

In high-risk areas, the use of external shading will be required. Internal blinds and curtains and tree foliage cannot be used for shading.

We recommend reading Part O documentation for full guidelines.

Planning permission

What is The Party Wall Act?

In addition to building regulations, you also need to know about the Party Wall Act 1996. The act is mainly to avoid disputes between neighbours and to help find resolve between two parties.

Under the Act, you're required to give notice to a neighbour in the following situations:

  • If you're building or excavating on, or near to the boundary of a neighbour
  • If you're working on a wall that separates your property from your neighbours

You do need to adhere to the Act separate to planning permission and building regulations. We recommend reading about the Party Wall Act here.

What is the neighbour consultation scheme?

In May 2019, the government made permanent the temporary rules for the size of extension that you can build under permitted rights.

If building a single-storey extension of more than four metres up to eight metres from the back of your house (for a detached house, six metres for semi-detached) you have a duty to inform your neighbour. Known as the neighbour consultation scheme.

Halfway between permitted rights and planning permission, the neighbour consultation scheme is a way to keep control of the bigger developments and avoid neighbour disputes.

Instead of speaking to your neighbour directly, you must contact the local planning office and they consult with your neighbours about your development. If your neighbour objects with a fair reason, the planning office can stop your permitted development.

Note, this is only for large extensions over four metres and you can still build up to four metres without having to go through this process.

If you're thinking of adding roof lights or adding new windows to your extension read about when you need planning permission and building regulations for windows here.

Planning permission

Other restrictions you need to check before building an extension

The Original House rule

Permitted development guidelines for adding an extension to your house refer to the 'original house'. This means the property as it stood on 1 July 1948 or on the date it was built if after. If an extension has been added to the original house then you have to factor this in to any development you can do under permitted development rights.

Article 4 Direction

A local council has the right to override permitted development rights. Check with your local office that there aren't any directives in place before you start planning your build.

Restrictive covenant

A property can have a covenant attached to it by a previous owner as a condition of sale. This can be a restriction of any development of the property or building in the grounds of the property. Your solicitor had a duty to inform you of this when you purchased the property so check with them that there hasn't been any previous covenants placed on your property.

Listed buildings

Subject to stricter planning rules a listed building needs listed building consent from your local planning office and the permitted development rights might not apply.

Designated land

Conservation Areas, National Parks, Areas of Outstanding Natural Beauty and World Heritage Sites. As with listed building properties built in designated areas are subject to tighter control and will need approval from the relevant authority.

More information

Information is correct at time of publication: Updated January 2023.

Planning rules are subject to change. Always seek approval from your local planning authority before starting any building work.

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