September 29, 2017

Re-purposing existing buildings

By Emma Kent

We don’t often work on projects on greenfield sites anymore, and so the chances are that any time we are engineering a new building, it is on the site of an old one! Often a key consideration at the early stage of a project is – do we demolish the existing building and create something new, or do we re-use what we can of the existing building to re-purpose and upgrade the existing space?

Creative re-use can mean different things to different clients and designers. It could mean taking a 1970s shopping centre, stripping it back to the structural skeleton and re-using the structure to create a modern shopping space.

Or it could be like our work at the London 2012 Olympic Media Centre, now known as Here East, working with Hawkins\Brown Architects. The International Broadcast Centre was built as a temporary venue for the media during the games, with the intention that it would be deconstructed after the games were finished – hence the light steel frame and simple, windowless cladding. It has been re-purposed with a fantastic new façade, a whacky paint job and several new internal floors. This has allowed a temporary building to become a permanent home to digital businesses such as BT Sport, UCL Laboratories and the Ford Smart Mobility Innovation Centre. The creative re-use involved a lot of clever engineering solutions – from justifying the re-use of foundations for greater loads, to coming up with ways to let natural light penetrate deep plan spaces, to upgrading the building services systems. By engineering its creative re-use, an average building was re-purposed into something spectacular.

Furthermore, construction accounts for 40% of the world’s materials and 75% of the world’s timber use. Re-using a building by refurbishing it, rather than demolishing and re-building, can make a huge saving in embodied carbon. Embodied carbon is the carbon dioxide emitted during manufacture, transport, construction and demolition of building materials. Understandably, repurposing a building does not mean that all waste or new material is eliminated, but the reductions can be significant. If we are a bit smart about things, we can also re-use waste in the re-development of the existing building.

As well as environmental benefits, there are human factors involved in the choice to refurbish rather than re-build. Places with architectural or historic merit, or even just local charm, can be preserved, maintained and enhanced. The historic One Aldwych Hotel, is Grade II listed and an icon on the Strand. With some thoughtful multi-disciplinary engineering upgrades, the basement space was stripped back to the bare structure, which was repaired and protected, then a contemporary new restaurant was inserted into the new open space.

Other human benefits from re-purposing a building include reduced disruption, noise, vibration and dust in the area. Don’t forget the human benefits to our clients, which often include large financial savings associated with re-using an existing building rather than paying for a demolition and new build!

Refurbishing a building can provide massive opportunities for upgrading the performance of a building as well as its looks. The carbon footprint of a building can be reduced through façade upgrades or replacement, improved plant design, better lighting and occupant-centred design. Issues with heating, cooling, lighting and ventilation can be addressed with a thorough refurbishment. Even adding an extra floor or two to create new lettable area can (sometimes!) be achieved.

The structure of a building is one of the key challenges for a building refurbishment. We need to establish if a building has the capacity for a change of use or modification, such as an additional floor. We also need to establish if the condition of a building is adequate to justify any refurbishment and an adequate future design life. The existing structural grid can be a challenge and accepting the location of existing columns is usually one of the compromises that must be made to re-use a building – although we can often use some structural gymnastics to remove the odd inconvenient column!

When a client asks us to look at re-using a building, we need to understand the size and position of structural elements. Laser scanning and point cloud surveys can generate geometrically accurate 3D BIM models of existing buildings. We use a combination of non-destructive and destructive testing to work out the capacity of materials such as concrete, masonry and steel. Ground penetrating radar can be used to find embedded elements and holes in impenetrably thick concrete slabs, masonry walls and filler joist floors. Because we are engineers we also like smashing things a bit, so, if we are allowed, within reason, so we also usually carry out some destructive testing for things like steel and concrete properties.

Creatively re-using an existing building to create something architecturally spectacular is the synergy between architecture, engineering and sustainability. We can preserve our heritage and streetscapes, as well as reducing the embodied carbon impacts of construction and buildings. There are cost and programme benefits to our clients, as well as reduced impact on the environment. There must be compromises along the way, but the future of the property industry involves a better understanding and use of the past, using the innovative engineering technology of the present.

This is just part one of Emma’s designing for re-use blogs, find out more about Cundall’s structural engineering capability on our website and keep an eye out for part two on Cundall Conversations coming soon!

Imagery: Here East © GG Archard

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Emma Kent, Structural Engineering, Sustainable Cundall

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