Broadcast Centre’s redevelopment features a facade of 3,000 glass panels, each of them unique – one of several remarkable challenges for Lakesmere and Laing O’Rourke.
Project: Broadcast Centre
Client: iCity (Delancey / Infinity joint venture)
Contract value: £150m
Main contractor: Laing O’Rourke
Architect: Hawkins Brown
Cladding subcontractor: Lakesmere
Start date: September 2015
Completion date: May 2016
Rarely can a glazed facade have been so difficult to construct.
Every single one of the 3,000 glass panels on the revamped International Broadcast Centre in London’s Olympic Park is unique – a necessity of the ‘dazzle’ frit pattern that wraps around the building.
“It is the single most challenging build element of the whole project,” says Mike O’Dell, construction manager for Laing O’Rourke, which is serving as main contractor on the 2012 media centre’s £150m redevelopment into a hi-tech digital hub, Here East.
The pattern is made up of more than eight million ceramic dots, digitally printed onto the glass at different diagonal angles across 9,000 sq m of curtain walling.
The Hawkins Brown design was inspired by the ‘dazzle camouflage’ used on battleships during the First World War. It is the signature feature of the 850,000 sq ft industrial-style building, with the dark interior of the Broadcast Centre opened up by the glazed facade to reveal orange structural steelwork inside.
Envelope specialist Lakesmere has had the daunting task of turning the architect’s vision into reality.
Project manager Martin Saltern explains: “Many buildings with glazed facades have a pattern on the glass, but it is usually uniform and can be repeated from panel to panel. But here, they are all different. It has had huge implications for the design, manufacture, delivery and installation.”
The double-glazed, unitised curtain walling runs around the north, west and south elevations, and is a structural part of the building’s envelope. The dots on the glass vary in density according to the solar gain requirements of different internal areas. The pattern is denser on the west and south elevations to reduce glare from the sun, where the glass also has a solar control coating, and more sparse on the north side to maximise natural light.
“On a typical project, you would expect 5-10 per cent of glazed units to be broken during the delivery and installation. But for any that broke here, we had to reconstruct the exact same unit”
Martin Saltern, Lakesmere
Planning the design of the panels required a lead-in of 40 weeks. The first challenge for Lakesmere was transposing the Hawkins Brown pattern into 2D drawings in Autocad.
“Our design manager Simon Summers and his team had to spend a huge amount of time working with the architect to ensure the pattern was aligned across the facade,” Mr Saltern says. “Fine-tuning was required to allow the pattern to fold around the corners and accommodate joints between panels.”
Like photocopying glass
The digital printing of the glass was carried out by Lakesmere’s Polish-based supplier Press Glass. “They use a Diptech laser printer to apply the dots on to the glass,” Mr Saltern explains.
“It then goes through a heat-treating process to strengthen the glass and bake the digital frit on to the surface. Press Glass describes the process as ‘like putting a piece of glass through a photocopier’.”
The glass was then transported to Lakesmere’s manufacturing subsidiary in Northern Ireland, McMullen Facades, which fabricates the units and bond in the glazing. At peak, McMullen’s factory produced nine units per day.
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The unitised system itself is bespoke and has a high number of variations. “Usually, the frames we use are pretty standard,” Mr Saltern points out. “But there are around 200 variations here – from the largest frames, which are 6 m x 1.6 m, to the smallest, at 0.5 m x 1 m.”
The delivery schedule – McMullen’s trucks arrive three times a week, bringing between 12 and 18 units each time – has required military precision. Each unit was given its own identification number, and arrived on site to fit with Lakesmere’s carefully planned installation sequence.
The identification numbers were also important in case of breakages. “On a typical project, you would expect 5-10 per cent of glazed units to be broken during the delivery and installation,” Mr Saltern says.
“Which is not a problem if they are all standard sizes. But for any that broke here, we had to reconstruct the exact same unit. Press Glass have been able to give us a turnaround time of four to five weeks for any breakages.” He says there have been five to six breakages in transit, and a few on site.
200 tonnes of stiffening steel
To accommodate the new glazed facade, which replaces metal-skinned Eurobond cladding panels, the Broadcast Centre has had to undergo major structural alterations.
“The structural frame was built as a portal frame and wasn’t designed to have this kind of glazed facade on it,” Laing O’Rourke’s Mr O’Dell explains. “So we so have had to stiffen the building. This has included putting in about 200 tonnes of extra steelwork and 50 CFA piles around the perimeter.”
“We have effectively constructed a new building structure inside another building”
Mike O’Dell, Laing O’Rourke
To attach the facade units on the structural frame, Lakesmere bolted brackets onto the steelwork and, in some cases, the floor slabs. Halfen channels were cast into the slabs, with locked-in T bolts, and the brackets attached to them.
However, an unexpected issue was that the existing floor slabs, revealed once Laing O’Rourke had peeled away the old cladding, did not quite match what was on the drawings.
“On the north elevation, we were expecting the floor slab to extend out a further 200 mm than what turned out to be the case,” Mr Saltern says. “So we had to devise a cantilever system, whereby the brackets were attached to 600 mm-long galvanised steel plates, which were cantilevered off the slab. We had to install about 300 of these plates in total.”
The units were lifted into position using a new-to-the-market spider crane, supplied by GGR. “The Unic URW1006 is the biggest spider in the country – with a capacity of 10 tonnes, a 30.7 m lifting height and 24.3 m working radius,” he says.
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“This reach allowed us to access every part of the building required without needing mobile cranes. We also used GGR’s Unic URW706 spider, which is the second biggest in the country – with capacity of 6 tonnes, lifting height of 19.5 m and working radius of 18.6 m.”
The spider cranes use a hydraulic vacuum lifting system that picks up the units and lifts them onto the building, where they are attached to the brackets by Lakesmere’s site team. The panels were designed to interlock with each other.
BT Sport redefines ‘live’ site
A further challenge for both Laing O’Rourke and Lakesmere has been the presence of BT Sport, which moved in to the Broadcast Centre back in 2013, throughout the build process. “They have a live studio broadcasting 24 hours a day, so we have had to schedule our work around them,” Mr Saltern explains.
Other end-users who will move in once Here East is completed include Loughborough University, data centre firm Infinity (also part of the joint venture developer client) and Hackney Community College.
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To accommodate their differing requirements, Laing O’Rourke has had to carry out numerous other structural alterations, reconfiguring what was effectively a giant warehouse with only one internal floor into a mixed-use internal space with four floors along the north and south elevations, and three on the west.
“We have effectively constructed a new building structure inside another building,” Mr O’Dell says.
Lakesmere has now almost completed its 32-week programme. Looking along the curtain walling at the frit pattern, Mr Saltern says: “I can’t help thinking that when other architects see this, they will want to use the same digital printing process for their facade designs.”
As well as the Broadcast Centre, the Here East development includes the 250,000 sq ft former Press Centre and a 750-seat auditorium. Laing O’Rourke is due to finish its own 76-week construction programme in May, leaving behind a unique addition to the Olympic legacy.
Challenging extra elements
Besides the glazed facade, Lakesmere’s £13m package has included several other elements of the building envelope. Around 300 sq m of the facade is covered with 113 punched aluminium panels, manufactured in Germany by Pohl, which had to accommodate the dazzle pattern in their design.
The facade is also broken up by several steel-framed grills, in keeping with the industrial look, which Lakesmere describes as resembling “hangar doors”. Each one is 17.5 m in height and 8 m wide.
Depth is provided by recessed and projected balconies, the latter using the same orange steel as the building’s frame. These are 3 m deep and range in length from 12 m to 20 m.
“The recessed balconies are part of Lakesmere’s package,” Mr Saltern says. “Our curtain walling steps back to create the line of the balcony, but it is the same facade system at the back of the balcony.
“The bases of the projected balconies were bolted on to the structure by Laing O’Rourke, and as these penetrations go through our facade, we have had to fine-tune the facade in these areas with a layer of insulation to avoid cold bridging and a silicon seal. The balustrades will be added once the landscaping around the building is finished.”
Additionally, Lakesmere has fitted a building-height internal atrium, which uses steel-framed curtain walling with fire-rated glass supplied by Pyroguard, and cut 33 polycarbonate roof lights into the existing roof covering.