In 2020, the government introduced a permitted development right allowing additional floors to be added to certain detached blocks of flats. The aim was to increase housing supply in built-up areas without requiring a full planning application.
The right is set out in Part 20, Class A of the General Permitted Development Order. Although it is permitted development, it is not automatic. You still need to apply to the council for prior approval, and councils regularly refuse these applications.
When the right applies
The permitted development right is subject to a number of conditions. In broad terms:
- only fully detached blocks of flats can be extended;
- the building must have been purpose-built as flats (not converted from another use);
- the right does not apply in conservation areas or similar designated locations;
- the building must have been constructed between 1 July 1948 and 5 March 2018.
If any of these tests are not met, the right does not apply and a full planning application will be required instead.
Prior approval and what the council can assess
Even where the building is eligible, an application for prior approval is required. This allows the council to assess the proposal on a limited range of issues, including:
- design and appearance;
- impact on neighbouring properties;
- highways and parking;
- flood risk and contamination.
Councils often refuse prior approval on the basis that an additional storey would harm neighbours through loss of light or outlook, or would appear overbearing or out of place.
What councils cannot assess
One of the key differences between prior approval and a full planning application is what the council is not allowed to consider.
Under Part 20, the council cannot:
- require private amenity space;
- require affordable housing contributions;
- impose wider policy requirements relating to energy, biodiversity or similar matters.
The application is therefore much more tightly focused.
Evidence matters
In practice, many refusals turn on neighbour impact. Where this happens, it is important that any refusal is backed by evidence.
We regularly see cases where councils refuse prior approval without submitting any technical assessment to support their concerns. Appeal inspectors tend to give little weight to generalised assertions where they are not supported by daylight, sunlight or other objective evidence.
We recently secured permission on appeal for an additional storey under Part 20 after a council refused prior approval without evidential support.
Is your building suitable?
The key questions to ask at an early stage are:
- was the building purpose-built as flats?
- when was it originally constructed?
- is it in a conservation area?
- can the additional storeys be designed to sit comfortably on the existing building?
- can neighbour impacts be properly addressed and evidenced?
If the answer to these questions is not clear, taking advice early can avoid wasted time and cost.
