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Prior approval for house extensions


This guidance note only applies to permitted development arrangements introduced for single storey extensions to the rear of a dwellinghouse.

Temporary arrangements

For a dwellinghouse that benefits from permitted development rights, single storey extensions at the rear of a house can be built up to the following limits under permitted development rights:

  • Where the extension does not project more than 8 metres beyond the rear wall of the original house on a detached property and 6 metres on any other type of property.
  • Where the extension does not exceed 4 metres in height.
  • Where the extension is within 2 metres of the boundary of the house, the eaves are not more than 3 metres in height.

Note: To benefit from the new allowances, you must submit a prior approval application. It is not possible to build up to the new limits without any formal consent (which is usually the case for rear extensions up to 4 metres on a detached property and up to 3 metres on other properties)

General rules that apply to all extensions:

The enlargement of a house through any extension (or conservatory) is not permitted development if:

  • Over 50% of your curtilage, (i.e. garden land) would be covered by buildings.
  • The height of the extension would be higher than the highest point of the roof of the original house.
  • The height of the eaves of the extension would be higher than the eaves of the original house.
  • It would include a balcony, veranda or raised platform/decking that is over 30 cm in height.

Conditions applicable to all extensions:

Extensions that comply with the permitted development criteria must be built from materials that are similar in appearance to those used on the exterior of the main house (except for a conservatory).

Prior approval

A ‘prior approval’ procedure has been introduced for single storey rear extensions proposed under the temporary arrangements (ie. those which would extend between 4 and 8 metres beyond the original rear wall of a detached house, or between 3 and 6 metres beyond the original rear wall of any other house).

The new prior approval procedure requires a developer to provide some basic information about a proposed extension and involves a process of consultation with immediate neighbours. We have 42 days to make a decision on a prior approval request.

View the Notification of a Proposed Larger Extension form.

Information requirements

Before beginning a development, you must provide the following information to the council:

  • A written description of the proposal including: (i) how far the extension would extend beyond the rear wall of the original dwelling; (ii) the maximum height of the extension; and (iii) the height of the eaves of the extension.
  • A plan indicating the site and showing the proposed extension.
  • The addresses of any adjoining properties (those which share a boundary).
  • The developer’s address and email if applicable.

We will not accept applications if any of the above information is missing. To make things easier, a Prior Approval for a Householder Extension application form is available here. Requests for Prior Approval are free of charge.

Note: Scaled plans are not a specific requirement for a Prior Approval request, however we strongly recommend the use of scaled plans including details about the location of all windows in the extension and potential losses of trees so that any neighbours are made fully aware of the specifics of your proposal. Accurate, scaled plans may also help to avoid objections from neighbours on the grounds of lack of information.


When a request for prior approval is received with all the required information, we will notify owners or occupiers of any adjoining properties about the proposed development, by letter. A copy of the notification is also sent to the developer. The adjoining owners or occupiers are given 21 days to comment on the proposals and any objections have to be made either in writing or by email. If neighbours are concerned that their comments will not be received in time by post, they should email us at

The notification letter will include:

  • Dimensions of the proposed extension.
  • The address of the proposed development.
  • The date the prior approval request was received and the date when the application expires.
  • The closing date for any comments.
  • Full details about how to comment on the proposals including our email address.

Prior approval is required:

When any owner or occupier of an adjoining property objects to the proposed extension, the prior approval of the council is required. We then have to make a decision as to whether prior approval should be given, or refused. In these circumstances we:

  • have to consider the impact of the extension on the amenity of all adjoining premises, not just the source of the objection.
  • may ask for further information to enable us to fully consider the impact on the adjoining properties.
  • have to take into account any comments made.
  • will visit the site to assess the proposals.
  • make an assessment on a case by-case basis.
  • issue our decision within the 42-day period.

Prior approval is not required:

  • When no objection is received from any owner or occupier of any adjoining property; and once the 21 day consultation period has expired. We will issue a decision that prior approval is not required.
  • If we fail to make a decision within 42 days from the date we received the submitted information, the application expires and prior approval is deemed to be given.

Building the extension

The extension should not be begun before one of the following occurs:

  • The developer receives notice from us that prior approval is not required;
  • The developer receives notice from us that our prior approval is given; or,
  • The 42-day deadline has passed and the developer has received no notice as to whether prior approval is given or refused.

Building in accordance with the approval:

The extension must be built in accordance with what has been agreed unless the council and the developer agree otherwise, in writing:

  • Where prior approval is required, the extension must be built in accordance with the details agreed with the council.
  • Where prior approval is not required, or the application has expired, the extension must be built in accordance with the original submitted information.

Building Regulations

Most building work requires approval under the Building Regulations although there are some exemptions for minor works. You should contact the council’s Building Control team to ensure that any alterations you propose comply with the latest standards.

The Party Wall Act

If you intend to undertake works on, or affecting, the party wall, you may need to notify adjoining owner(s) and reach an agreement before work is undertaken. 

Further advice

If you are still unsure about your permitted development rights, please contact us