New permitted development right to add two extra floors to blocks of flats

The government has introduced a new permitted development right allowing developers to add two extra floors to detached blocks of flats.

The new permitted development right comes into force on the 1 August 2020 and is set out as Class A, Part 20, Schedule 2 of the General Permitted Development Order (the GPDO). The wording of the legislation in full can be viewed here.

The key points to understand are:

– Only fully detached blocks of flats can be extended.

– Only purpose-built blocks of flats can be extended – they must have been built as flats and only as flats (not converted from a house or office, for example).

– The right does not apply in conservation areas or similar (world heritage sites etc);

– The building must have been constructed between 1 July 1948 and 5 March 2018 (this rules out blocks built very recently, but also older buildings (such as Victorian mansion blocks)).

– You must make an application to the council for ‘prior approval’. The council can assess the proposal on its:

  • design and appearance
  • the impact on neighbours
  • highways and parking
  • flooding
  • contamination

– The council will therefore refuse the application if it feels the design is poor quality, the development will look out of place or neighbours will suffer a loss of light, outlook or privacy.

– There is a fee of £334 per new flat.

– The advantage of the new regime, compared to applying for full planning permission, is that the LPA cannot assess the size of the flats (there are no minimum sizes), require minimum outside space, require affordable housing contributions or apply other bothersome policies relating to, for example, biodiversity, energy efficiency etc.

– The main questions that developers should ask themselves are:

  • Was the building ‘purpose-built’ as a block of flats?o When was it originally built?
  • Is it in a conservation area?
  • Can the new extension be designed to fit in with the area?
  • Will the extended building cause any harm to neighbours?

To help you understand and take advantage of this new permitted development right, Just Planning is offering a site appraisal service. We will provide you with detailed advice on the specific requirements of the new legislation and will apply it to your building, to give you an idea of whether it is eligible and whether the council might grant you prior approval to add extra floors.

We can also recommend architects with experience of designing rooftop extensions to existing buildings. Contact us at for more information.