Permitted Development policy updates (Sept 2020)

What is Permitted Development?

Permitted Development is a list of criteria for building development that does not require Planning Approval.   A previous blog of mine discusses the Top 10 Criteria for Permitted Development.   These top 10 rules continue to apply, while a collection of new policies expanding potential development have been introduced.

The new rules feature a focus on opportunities for new dwellings in various situations, which I will discuss in a separate blog, and additional development rights for existing dwellings that I will discuss below.   For existing dwellings, the additional rules allow for upper-floor extensions that previously required planning permission.  

What is changing and what does that mean?

Extensions to dwellings;

Over and above the previous policies and guidelines, this revised set of policies allows additional storeys to be added to existing dwellings, subject to certain criteria.   There are two key categories where this additional development can apply:

  • Up to two additional storeys, where the existing dwellinghouse consists of two or more storeys
  • One additional storey, where the existing dwellinghouse consists of one storey

In plain language, this means that bungalows (with only one storey – excludes where a loft conversion has already been added) can have one new storey added and a house of two or more storeys can have up to two further storeys added (again, unless the house has previously had storeys added on top).

There are some qualifying criteria for such developments, and it will not be permitted if:

  • The dwellinghouse has previously been granted permission through a change of use (Class M, N, O, P, PA or Q)
  • The dwellinghouse was constructed before 01 July 1948 or after 28 October 2018
  • The development is not part of the principle part of the dwellinghouse
  • The height of the development for a single-storey dwelling is more than 3.5m above the highest part of the principle roof
  • The height of the development for a two-storey or more dwelling is more than 7.0m above the highest part of the principle roof

There is an interesting qualification on height with regard to semi-detached and/or terraced houses.   For semi-detached houses, you can only raise the height of your dwelling house by 3.5m above your neighbour’s roof and for terraces no more than 3.5m above the highest roof in the terrace.

The ‘Principle Part’ of the dwelling house can be understood as the original main part of the house.   These policies do not allow for development over extensions to the house.  

Other qualifications require the development to include, though not exclusive to:

  • Matching external materials
  • No windows to side elevations
  • Seek Prior Approval where criteria such as design, and amenity will be assessed


Therefore, if your house was originally constructed between 01 July 1948 – 28 October 2018 and not granted permission through a change of use then you can add additional storeys to your dwellinghouse, providing it is only formed on the principle part of the dwelling house.   The key understanding is that any development under this criteria is formed on top of the existing dwellinghouse and not creating any new footprint.   It cannot be applied to upper floor extensions over existing extensions.

Generally speaking, the policies appear, at first glance, quite open as if enabling development that could read very significant in a street scene, whereas in actual fact they are carefully controlled and ultimately governed through a Prior Approval Notice.

There are likely to be many other questions, over and above these here.   Please feel free to add any questions as comments or contact us directly at

Click here to read the legislation in full.

Article was written by Laurence Wright of BBD-architects on 12Oct20