The housing challenges facing London are well documented::

• London needs around 50,000 new homes a year, but housebuilding is running at around half that.
• Between 2005 and 2015, private rents in London rose by an average of 35%.
• Future projections suggest there will be 9m people in London by 2020, 10m by 2030 and 11m by 2050.

There are now serious concerns that the lack of affordable housing and rising rents risk driving key workers out of London, and may cause businesses to think twice about locating in the capital. But as well as triggering dire warnings about the future of London and the UK economy, the housing crisis has also prompted increasingly creative ideas on how to solve it.

Going up

Last year, Darren Johnson, who represented the Green Party on the Greater London Assembly, proposed five ideas to secure land for affordable homes. One of his proposals was to build additional storeys on top of existing buildings.

Johnson suggested that this approach has many advantages over demolishing existing properties and building new homes, including:

• a shorter period of disruption for residents;
• more environmentally friendly than demolition and rebuilding
• an opportunity to refurbish the existing homes

He offered the example of the Ducane Housing Association in Hammersmith, which built 44 new homes on top of two 1970s buildings. Based on data from London’s Borough Councils, Johnson estimated that almost 50,000 new homes could be built using Ducane’s example.

One potential stumbling block is the difficulty of getting planning permission for intensive construction projects in the heart of active communities. However, in July 2015, the Treasury signalled the government’s intent to end the need to obtain planning permission for upwards extensions in London.

Building on public buildings

Another approach, on similar lines, is the idea of building new homes on top of publically owned buildings. In 2015, WSP professional services consultants conducted a survey to gauge interest in the idea. Among their findings:

• 61% of respondents supported the idea of allowing private developers to refurbish government buildings, allowing them to make their money back by building additional housing on top of the refurbished building, which they could sell for profit.

• Over 60% of Londoners would happily live above a library, while 44% would be willing to live above a government administration building, and around a quarter of Londoners would be willing to live above a school or hospital.

The WSP report went on to suggest that developing all available sites by building apartments above all available public buildings in London could provide over 630,000 residential units.

“Of course we acknowledge that not every building will be able to be redeveloped in this way, but even targeting one in every two municipal buildings could go a long way in solving the housing crisis, providing 315,000 homes.”

These homes, the report argued, would be most suitable for key workers employed by these facilities, or by students, older people and young professionals. Some may even house those working in the facilities below.

One landlord is already exploring the idea with several London councils. Apex Housing Group has experience of converting airspace above properties into luxury penthouse apartments. Managing director Arshad Bhatti believes the principle could be applied to affordable homes:

“We are working with a number of local authorities across London and expect airspace development projects will help bridge the gap between demand and supply of new homes in London – crucially with minimum lead times, and offering maximum value for property owners.”

The view from overseas

The idea of building up may be relatively new to London, but other densely populated cities have already been exploring its possibilities.

• In Rotterdam, developers have been combining ultra-lightweight materials to build apartments on top of a 1940s shopping centre.
• In New York, a developer is planning to construct a nine-storey condominium on top of apartments dating from the 1950s.
• In Paris, three prefab dwellings attached to the rooftops of existing buildings were completed in January 2016.

The architects of the Paris project believe it has multiple benefits:

“Building on top of the roofs is not only an ecological and economical solution, it’s working against the urban sprawl that kills the social link. It’s also a contemporary way to discover new perspectives of the city, a new Paris above the horizon.”

But not everyone is happy with the idea. Residents in the existing apartments beneath the proposed New York condominium are concerned that the wear and tear of construction could damage their properties. And they’re also worried about the stability of the columns supporting the new building.

The only way is up?

Clearly, building on existing properties is not without its problems. But as the housing crisis in London intensifies, and spreads to other parts of the UK, it’s an idea that may no longer be regarded as pie in the sky.

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If you liked this post, you may also be interested in other blog posts on suggestions for tackling the UK housing crisis:

• Support for the squeezed middle: could public subsidies tackle London’s housing crisis?
• New ideas for housing in London
• Can Housing Zones help the housing crisis?