New Permitted Development Rights – Building Upwards not Outwards

New rights to build upward extensions to certain buildings form a key part of the UK government’s recent reforms to the planning system with a focus on stimulating regeneration of towns and cities and delivering homes more easily as part of the response to the Covid-19 pandemic.

The permitted development (PD) rights fall into two categories: new rights on existing, purpose-built detached blocks of flats; and new rights on individual homes.

Householder Extensions

Home-owners will now be entitled to increase the size of their homes by adding:

  • Up to two additional storeys, where the existing house consists of two or more storeys; or
  • One additional storey, where the existing house consists of only one storey.

There are a large number of restrictions on the operation of this right, including if the house was constructed before 1 July 1948 or after 28 October 2018, if additional storeys have already been added to the original house, and if following the development, the height of the highest part of the roof does exceeds 18 metres, development will not be permitted. Any development will need to comply with a number of conditions. For instance, the external materials used must be similar to those used on the host property and that it must not include a window in any wall or part of the roof on a side elevation of the house.

Demolition of Commercial and Industrial Premises for New Homes

New permitted development rights allow vacant and redundant free-standing commercial and light industrial premises, and residential blocks of flats, to be demolished and replaced with new dwellings. A new Class ZA Permitted Development Right has been introduced, for the demolition of buildings and replacement by either a single purpose-built detached block of flats, or a purpose-built detached house

  • There are a number of restrictions on this right and of particular note, where the above Class ZA development will not apply, are the following:
  • If the old building was constructed after 31 December 1989;
  • If the building is listed;
  • If the footprint of the building exceeds 1,000 square meters; and
  • Unless the old building has been vacant for at least 6 months immediately prior to the application for prior approval.

Flat Extensions

Permitted development rights have the effect of granting planning permission automatically and upwards extensions of existing blocks of flats are now included in the system. To qualify, existing blocks of flats need to be:

  • detached
  • purpose-built between 1948 and 2018
  • three storeys or more above ground level

New upwards extensions are limited to two storeys and the building should not be more than 30 metres high after the extension.  Other restrictions exclude the extension of listed buildings and buildings in proximity to aerodromes.


These new permitted development rights have attracted concerns regarding the quality of homes. Previous permitted development conversion schemes do appear to create worse quality residential environments than planning permission conversions. This is as a result of a lack of regulation regarding the government’s nationally-described space standards and a lack of natural light to windows and limited access to outdoor amenity space. The government’s own Building Better, Building Beautiful Commission also concluded that permitted development rights had “permissioned future slums”.

During the recent lockdown we have all acknowledged and appreciated the importance of indoor and outdoor space in our homes as the amount of time we spent in lockdown has increased. It is hoped that with the new permitted development rights, some form of control regarding the quality of extensions and conversions and a maintenance of minimum space standards to ensure high quality environments are created. These recently introduced measures indicate streamlining the delivery of housing is currently prevailing over prioritising the delivery of quality.