Canary Wharf Crossrail
Structural Award Winner 2015
Client/Owner: Canary Wharf Group
Architect: Foster + Partners
Structural Engineer: Wiehag, Seele, Arup
Main Contractor/Builder: Canary Wharf Contactors
Landscape Consultant: Gillespies
Wood Supplier: Wiehag
Wood Species: Spruce
In 2008, Foster + Partners were commissioned to design a mixed-use scheme encompassing the over-ground elements of a new station for the Crossrail project at Canary Wharf. This will form a new enclosure unifying the station and other elements including new retail units and a park. The design is characterised by a landscaped, sheltered park on the roof, accessible from ground level by connecting bridges. Wrapping over the lower concrete superstructure, this 300 metre long timber lattice opens in the centre to draw in light and rain for natural irrigation.
Four levels of shops, cafes and amenities sit above the underground station, the arcade making use of natural light to minimise energy consumption and welcome people into the building. When open at night, the park will be lit, illuminating the timber lattice from below and creating a welcoming glow through its ETFE outer skin.
Timber was first proposed as an appropriate material to enclose the park – it is organic in nature and appearance, strong, adaptable and can be sustainably sourced. It also clearly differentiates this building from others on Canary Wharf’s estate, which are predominantly stone, metal and glass. Timber has a great nautical and architectural history on the Wharf and this building is uniquely situated within the waters of West India Dock.
Pre-tender advice from timber specialists (suppliers and consultants) was that either larch or spruce was best suited for the design. There were a number of determining factors as part of this including design/service life, resistance to weather, technical characteristics relating to glulam fixings of steel plate and cost.
A key characteristic of the building is that the roof has varying levels of exposure – from fully exposed without any ETFE cladding on top to virtually full cover. There are also instances where the roof covers plant rooms.
All timber needs to be protected from direct exposure to UV and water otherwise it goes black. Larch weathers more slowly than spruce but both will go black eventually if exposed. The weathering process can be delayed through the use of a coating but most coatings need to be reapplied regularly which is an ongoing maintenance issue. There was one extremely tough coating that was considered but this was so thick that it made the timber look like plastic.
Foster + Partners tendered for larch and spruce. Some of the tenderers raised issues with larch and the use of glued-in rods to make the connections to the nodes; one tenderer actually advised against it altogether. Lead times for larch were longer and the cost for larch was considerably more expensive. As a result, the Client confirmed that spruce was their preferred timber choice. The timber comes with a temporary coating to protect it during installation.
Further Sustainability Information: In combining complex modelling with an iterative design process and taking advantage of computer aided manufacturing, the project demonstrates how timber can be used with a high degree of precision to deliver a technically advanced, sustainable public building. Timber is FSC certified.