Offsite brings weight to the case for rail overbuild

Offsite brings weight to the case for rail overbuild

Following our research into the benefits of building over rail lines to ease the UK housing crisis, UK strategic growth director Bill Price explores how the lighter solutions of offsite modular construction could benefit rail overbuild projects.

Our report Out of Thin Air – One Year On explored the potential of rail overbuild to help overcome London’s housing shortage, identifying over 2,356 hectares of available rail land in London which could provide new homes.

Rendering of Principal Place a high rise tower in London - front view
Principal Place credit Brookfield

Rail overbuild is just one of a range of methods to densify and create land for homes. But, using offsite techniques to provide lightweight, modular housing and make the process quicker, safer and more economical is worth a rethink.

For one thing, manufacturing building components to be trucked in for assembly on site means they’re less subject to weather damage than at exposed construction areas. It’s also a faster building method – you can prepare the site while the homes are being built elsewhere.

Safety is the first priority when building over live rail tracks. Overbuild is achieved by first constructing an encapsulation – a sort of concrete box – around the railway, to separate the overbuild construction works from the operational trains. Building the components for the encapsulation away from the train line, to be put in place when the trains aren’t running could further reduce the risks.

image of buildings in the city

Then, there are the homes themselves.

Weight is understandably important when you’re building over an existing structure – and the new offsite systems and materials are frequently lighter than those of traditional home-building. Using offsite modular construction methods could cut the weight of a five or six storey overbuild by around 40-50%. The encapsulation and foundations could then be designed to bear less load, with volumetric modular structures or pods quickly assembled onsite and lifted from trucks right onto the overbuild.

Overbuild is a complicated, subtle idea and brings together our experts in everything from rail and civil engineering planning to stakeholder engagement. We talk to colleagues across the world to seek out best practice and continue our research. We’re even writing a rail overbuild guide for Build Offsite to help demonstrate how all the elements fit together to produce better value and quality with lower cost.

Typically, we find the more answers we provide, the more enquiries we get. But we’re fine with that.

Interested in talking to us?