What is the new right?
From 31 August 2020, a new permitted development right will allow you to construct up to two additional storeys to dwelling houses consisting of at least two storeys, and one additional storey to one storey dwelling houses. The new storeys must be immediately above the topmost storey. The right also covers any engineering operations reasonably necessary for construction comprising works within the curtilage to strengthen existing walls or foundations. There are provisions as to what constitutes a storey in terms of basements and roof accommodation.
Perhaps surprisingly, the rights do apply to listed buildings. However, listed building consent will be required for any works that affect the building’s character as a building of special architectural or historic interest.
https://www.legislation.gov.uk/uksi/2020/632/regulation/22/made