Upward Extensions of Existing Homes to create more space within the same dwelling

The Government have made potentially sweeping changes to permitted development rights in England.In this post we consider the proposed new permitted development right allowing householders to add potentially up to 2 additional storeys on their residential dwelling without planning permission. The draft legislation is here and the changes are due to come into effect on 31 August 2020.The legislation will introduce a permanent permitted development (PD) right (Part 1 Class AA)  to allow existing houses which are detached, semi-detached or in a terrace to be extended upwards to provide additional living space for the existing dwelling by constructing additional storeys as follows:

  • of up to 2 additional storeys can be constructed on the topmost storey of a detached house of 2 storeys or more, or 1 additional storey can be constructed on a detached house of 1 storey, above ground level.
  • In a terrace of 2 or more houses (which includes semi-detached houses) up to 2 additional storeys can be constructed on the topmost storey of a house of 2 storeys or more, or 1 additional storey can be constructed on a house of 1 storey above ground level. Existing accommodation in the roof space of the existing house, including a loft extension, is not considered as a storey for the purposes of this PD right.

There are a number of exemptions from/limitation to the use the new Part 1 Class AA residential extension right including, but not limited to:

  • A maximum height of 18 metres about ground level, with a maximum 3.5m and 7m increase where the original house is one and two storeys respectively;
  • The roof pitch of the principal part of the house must not alter;
  • External materials must be of a similar appearance to the existing exterior;
  • Where the house is in a terrace its height cannot be more than 3.5 m higher than the next tallest house in the terrace. To prevent overlooking a window cannot be installed in a wall or roof slope of a side elevation of an additional storey built under this PD right. As with existing permitted development rights to extend or alter houses the external appearance of the materials used in the construction of the additional storeys must be of similar appearance to that of the existing house;
  • The new PD right only applies to existing dwellings built between 1 July 1948 (when the current planning system was created) and 28 October 2018 (when the proposal to introduce a permitted development right to extend existing houses upwards was first announced);
  • Homes extended using this right cannot be in use as a C4 small house in multiple occupation, or change to that use. This means that an application for planning permission would be required for a home extended under the right to construct additional storeys to become a house in multiple occupation;
  • The development cannot include any engineering operations other than works within the curtilage of the existing house to strengthen existing walls and foundations;
  • The existing residential use has been granted via previous permitted development rights;
  • Listed buildings; and
  • Homes in Conservation Areas, National Parks and the Broads, areas of outstanding natural beauty, or sites of special scientific interest.

Where any development under Part 1 Class AA is proposed, the developer must first apply to the local planning authority for Prior Approval providing information on the following:

  1. impact on the amenity of any adjoining premises including overlooking, privacy and the loss of light;
  2. air traffic and defence asset impacts of the development;
  3. the external appearance of the building, including the design and architectural features of- the principal elevation; and- any side elevation that fronts a highway; and
  4. whether, because of the siting of the building, the development will impact on a protected view.

When a local planning authority receives such a Prior Approval they must notify each adjoining owner or occupier about the proposals, including the maximum height of the additional storeys, and give them 21 days to comment.Any Prior Approval will be subject to the following conditions:

  • That the redevelopment must be completed within 3 years from the grant of the prior approval;
  • Pre-commencement condition for the agreement with the local authority of a construction management report (including how to mitigate adverse impacts of noise, dust and vibration and the proposed use of materials), which the developer must then comply with when carrying out the development;

Notification of the completion date; andAny new dwelling house must remain as a C3 use, except if the other purpose if ancillary to the primary use as a dwelling house. Initial commentsWhen announcing this right the Secretary of State did stress that there will be a “requirement to carefully consider the impact on neighbours and the appearance of the extension" via the Prior Approval regime. However, we note that the draft legislation only requires consideration of and consultation with adjoining neighbours - we would suggest this term is currently unclear and guidance would be welcomed.Also, unlike with other recent PD changes there does not appear to be a requirement to ensure the provision of adequate natural light within the additional storeys which is unfortunate. We would refer you our recent note here on a recent Government report which highlighted problems with PD authorised extensions.Like any other Permitted Development works, CIL liability (subject to exemptions and reliefs) will be applicable (if applicable in a given area) but affordable housing will not be. Given the extent of the recent PD changes to create residential dwellings we wonder whether the Government may alter the Planning Practice Guidance to facilitate some form of affordable housing provision.It is worth remembering that greater flexibility via permitted development rights does not mean that using them will be appropriate/possible, for example:

  • Are any restrictions within the existing planning permission(s) (i.e. condition on maximum building height) and associated section 106 planning obligations;
  • Is any current/historic enforcement action;
  • Signage/advertisement consent;
  • Building regulation requirements;
  • Right to light potential issues; and
  • Any restrictions imposed in the title documentation, including any lease, which would fetter the ability to use these rights.

If you have a site which you consider may benefit from this right our team of in-house chartered town planners are here to assist and are backed up by our specialist planning lawyers. You can find contact details here.We would also refer you to our other articles which note the key points and the potential impact of the other recently announced PD rights being:


The content of this page is a summary of the law in force at the date of publication and is not exhaustive, nor does it contain definitive advice. Specialist legal advice should be sought in relation to any queries that may arise.