Raising the roof

Canary Wharf is well-known for being home to a host of striking modern buildings but a new addition to its skyline is causing quite a stir

Concrete, glass and steel structures are commonplace at London’s Canary Wharf but the new Crossrail station which is under construction next to the HSBC tower is breaking the mould with a Glulam framed roof.

When complete the mixed-use scheme will comprise four levels under the water of the West India dock plus two levels above the water and a rooftop park all encompassed in an arched roof.

Work began on the project, which was designed by architects Foster + Partners, in 2009, and the roof garden and first phase of the retail and leisure space is set to open next year, three years before trains will run through the station.

An arched Glulam grid shell, by Austrian specialist Wiehag, covers the whole structure, wrapping round the building. The frame supports transparent ETFE cushions, produced by Seele, which are lighter than glass and filled with air and allow enough light to get through for the trees and plants in the garden below.

“I know from showing industry professionals around during the construction phase that this project has the wow factor unlike any other I’ve been involved in,” says John Spittle, Wiehag’s sales director for England and Wales. “Pictures do not do justice to the sheer scale and the amazing visual spectacle that the Glulam grid shell forms – especially as it curves out over the water at each end.”

The 300m long structure consists of nearly 1,525 Glulam members with a maximum length of 9 metres and 450 steel nodes connect the Glulam elements. Despite its shape there are only four curved timber beams in the whole structure and these are used at the cantilevered ends where there is a tight radius.

Parametric design is not new for Wiehag but it optimised the approach in collaboration with Foster and Arup during the design phase of the project. “We see Parametric design being used more and more in future for timber design, as the projects become larger and more complex,” said Spittle.

Instead of the traditional flitchplate/dowel solution or glued in threaded rods, Wiehag used a state-of-the-art technique of inclined fully threaded timber screws as Spittle explains: “With this technique we optimised the degree of prefabrication and installation, as well as offering a much neater solution.”

The coating used on the Glulam was specifically tailored for the project, to protect against water ingress during installation and UV damage, as well as against termites which it was felt might arrive in the UK during the building’s life span.

While many Glulam structures have been constructed in the UK nothing of this scale has been built in the capital before and the sheer scale of this project and its location in the heart of London’s finance district seems sure to put timber and indeed Glulam on the map.

“Iconic landmark buildings like the Canary Wharf Crossrail station are an important reference for the whole UK timber industry,” said Spittle. “A picture tells more than a thousand words and clearly demonstrates the ability of Glulam timber in combination with cutting edge structural design capabilities.

“We are confident it will help change people in the UK’s perception about what timber can do and which sectors it can be used in, as currently many feel timber is only suited to small domestic structures, whereas on the continent we have already constructed numerous infrastructure projects using Glulam, including aircraft hangers, communication towers, bridges and railway stations.

“Our vision for timber products like Glulam in the UK is that it is used as a mainstream product rather than just as a niche ‘eco’ product, and that it is not just used in high-profile projects like Canary Wharf, but in more day-to-day applications like factories and salt barns.”

This article first appear in the Winter 2014 edition of Timber & Ecoconstruct magazine