New permitted development rights for two-storey extensions of blocks of flats

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Back in March 2020, the Ministry of Housing, Communities and Local Government published a policy paper titled ‘Planning for the Future’. It set out proposals to rebuild a home-owning Britain and ensure security for those people who don’t own their own houses. The Government stated that it would introduce new tools to “support communities to densify and make best use of their under-utilised brownfield land”. This would include introducing new rules to encourage building upwards and consulting on new permitted development (PD) rights to allow vacant commercial buildings, industrial buildings and residential blocks to be demolished and replaced with well-designed new residential units which meet natural light standards.

The Government has now introduced new legislation, the 2020 Order [1], which inserts Class AA (enlargement of a dwellinghouse by construction of additional storeys) into Part 1, Schedule 2 of the GPDO 2015.  The new Class AA permits the construction of up to two additional storeys of residential accommodation on top of existing, purpose-built blocks of flats. Two additional storeys may be added where the existing dwellinghouse is two or more storeys tall, or one additional storey where the dwellinghouse consists of one storey.

The new PD rights came into effect on 1 August 2020.

Restrictions and exclusions

There are number of criteria which must be satisfied if a development is to make use of the new PD rights. These include:

  • The existing building must be a purpose-built block of residential flats;
  • The building must have been built between 1 July 1948 and 5 March 2018; and
  • The new storeys must comprise flats

The new PD rights only apply to blocks which were purpose built as residential flats and are not available to buildings which are in mixed use. If, for example, a small proportion of the building is office space, or if there are retail units on the ground floor, the PD right will not apply. Therefore, the new PD right is more likely to be used for low-rise residential blocks built specifically for use as flats, which are commonly located in smaller regional or seaside towns around the country rather than as developments in major cities.

If the planning permission for residential use of the existing building was obtained through another permitted development right, then the new PD rights are not available.  This means that, for example, office blocks or retail units which have been converted to flats under the GPDO cannot be extended upwards under the new PD rights.

There are also height restrictions which limit the new PD rights:

  • The additional storeys cannot exceed 3 metres in height or the height of any existing storey, whichever is the lesser;
  • The overall height of the roof of building (as extended) must not exceed 7 metres above the highest part of the existing roof; and
  • The extended building cannot exceed 30 metres in height.

The land on which the building is located is also limited. The building cannot be located on a site of special scientific interest, a safety hazard area, a military explosives area or within 3km of the perimeter of an aerodrome. Further, the PD rights do not apply to listed buildings or scheduled ancient monuments.

Conditions and prior approval requirements

As with existing PD rights, the developer must apply for prior approval from the local planning authority for certain aspects of the proposed development. These include the impact of the amenity of any adjoining premises (including overlooking, privacy and the loss of light), the external appearance (including the design and architectural features of the principal and side elevation), and air traffic and defence asset impacts. A report detailing the management of the construction must also be provided to the local planning authority. This is more onerous than the existing prior approval process, and it will also apply to other pre-existing PD rights.


There has been some criticism on this new PD rights to construct residential accommodation, due to the fact that a small number of schemes have previously delivered poor quality accommodation. The construction of additional storeys is also likely to cause concerns from surrounding neighbours about overlooking, obstruction of light and overshadowing.

Given that there will be limited circumstances in which the new PD rights may be exercised, it seems unlikely that they will be attractive to major developers looking to deliver large numbers of new homes. In practice, the PD rights may assist individual homeowners and smaller scale developers seeking to expand individual properties.

[1] The Town and Country Planning (General Permitted Development) (England) (Amendment) (No. 2) Order 2020 (SI 2020/755)