In October, London’s Southwark Council announced that it would be embarking on a programme to alleviate the district’s acute housing shortage and provide much-needed council housing to the 12,000 families on its waiting list. Their method, however, will be a rather novel one: the houses will be constructed on top of existing residential and commercial buildings, in a process known as ‘rooftop’ or ‘airspace’ development. To minimise the impact on existing residents of the chosen buildings, the homes are usually constructed off-site in a modular fashion before being assembled on the waiting rooftop.

A solution to the housing crisis…

The idea of rooftop development is gaining traction as a way of alleviating London’s housing needs, especially after a 2017 Housing White Paper explicitly mentioned it as a potential way forward. It would mean that developers wouldn’t have to pack even more buildings onto the capital’s already crowded floorspace – or build on precious green belt land. Specialist developer Apex Airspace has estimated that around 180,000 new homes could be provided in this way, including 60,000 on the roofs of public buildings. Similarly, recent research from property experts Knight Frank identified 23,000 buildings in Central London alone that could accommodate rooftop homes.

It would appear that the government has been swayed by these figures; Homes England recently awarded £9 million to Apex to construct 78 new rooftop homes on various sites across London, while Mayor of London Sadiq Khan has also provided the firm with a £10 million development loan to help in the delivery of quality, affordable housing.

… or pie in the sky?

Not everyone is a fan of the spreading popularity of rooftop developments, however. Jeremy Leaf, former residential chairman of the Royal Institute of Chartered Surveyors (RICS), recently went as far as to say that airspace development had the potential to transform otherwise pleasant areas of London into “rooftop shanty towns of ill-considered boxes”. He also added that developers weren’t taking into consideration the extra space that would be needed to provide essential additional amenities and parking to potentially tens of thousands of new residents.

Local councils are also dragging their feet in terms of granting the planning permission needed for airspace developments. While Apex Airspace aims to deliver 10,000 new rooftop homes over the next decade, it says it is currently managing to construct just a couple of hundred per year due to council resistance. And while former Chancellor Philip Hammond suggested plans to relax permission requirements by extending permitted development rights to upward extensions in his 2018 Budget speech, the results of a consultation published in May this year made it clear that these proposals would not go ahead.

A complicated business

Rooftop development, therefore, is not always an easy way forward and requires serious consideration. Is the building structurally suited to accommodate a rooftop building? Is there a need for significant adaptations before work commences? How can the impact on existing tenants and residents be mitigated? These are just a few of the questions that landlords and developers need to consider before deciding whether airspace development is a viable option.