Proposals to develop around a quarter of a million new homes in London by building apartments above rail lines has been broadly welcome by geotechnical specialist but some have warned that the challenges should not be underestimated.
The concept put forward by WSP’s “Out of Thin Air” report published today says there is the potential to provide all the new homes London needs if existing engineering techniques were used to construct apartment blocks directly above rail, overground and underground lines.
“We have to be more creative in using existing space in what remains a relatively low-rise city,” said WSP director Bill Price. “The air rights above rail tracks present an unrealised but significant opportunity to build more new homes on brownfield land. It’s important to emphasise the engineering is absolutely possible and not new.”
Asuc technical consultant John Patch commented: “The prospect of solving London’s housing crisis by building over train tracks is exciting, achievable and, most importantly, cost-effective.
“Clearly there will be geotechnical challenges but the UK’s geotechnical contractors are more than capable of creating value-engineered designs and economically viable installation methods to minimise disruption to transport and maximise load capacity.
“The foundations construction will be such a key element that geotechnical contractors need to be employed at least as joint venture partners and at a very early stage. Design will be more about innovative solutions and buildability.”
Another geotechnical specialist, who asked not to be named, told GE that over site development is nothing new but the scale and costs of such schemes are significant and a major project recently considered in east London would have come with a £100M price tag for the piling work.
“What I believe is holding wholesale development back is the expectation of value,” he said. “At least one over site development has been sent back to the drawing board because the affordable housing development planned didn’t fund the below ground redevelopment of the station, only a luxury residential and commercial development could be ‘sold’ at such a profit as to make the station redevelopment cost neutral.
“I think that you could say that the foundations industry is aware of a number of schemes being considered and is ready to take up the challenge, however, this challenge shouldn’t be underestimated.”
Another geotechnical expert pointed to the additional cost issues - currently estimated at £240M - that are currently being experienced with the over site development at Battersea on the Northern Line Extension to demonstrate the challenges such schemes present.
WSP has said that the thinking behind the report emerged after it was appointed by Network Rail in 2012 to study the feasibility of building above rail lines. The study’s conclusions, which focused on the type of decking and noise and vibration issues are detailed in the new report.
“There is a wider point about how we can better connect communities and unlock new homes not just above rail lines but adjacent to them as well. In some parts of London rail lines act as accidental segregators,” said Price. “By ‘decking’ over these lines, such as the proposed regeneration west of Earls Court underground station, we can join together sites to unlock an even higher number of new homes and create new vibrant communities.”