The city centre building plans document allows owners of urban buildings to construct new flats on their rooftops under permitted development. This would mean that they would not need to seek planning permission. The buildings would be allowed to grow as much as five storeys without approval. The new rule would not apply to listed buildings or those in national parks.

These so-called “air rights” have been fought for by developers as it is common practice in American cities and it could help to create tens of thousands of new homes. However, others have pointed out that poorly constructed additions could lead to boxes being placed on existing roofs that would damage the aesthetic look of UK cities.

Jeremy Leaf, the former chairman of the Royal Institute of Chartered Surveyors has said that the removal of the need for planning permission can only lead to a proliferation of ugly and poorly designed extensions, out of character with nearby buildings. He also points out that these additional homes would have no amenities or parking and could have poor light or overlook other homes.

This is a view shared by architects including Alex Depledge from Resi who says that the only people that will benefit will be leaseholders and developers who could become overnight millionaires. However, he does point out that it will dramatically increase supply and bring down house prices.