On the face of it

Southwark has been a centre of construction innovation for thousands of years. It is here that the Romans first bridged the Thames and the site of London’s original gothic cathedral, complete with flying buttresses. More recently the Tate Modern art gallery, carved out of a disused power station, and the elegant millennium bridge – now dewobbled – have confirmed the borough as a magnet for quality design.

Bankside 1, dubbed the ‘Blue Fin’ building, adds to this mix. But it’s not only the finished article that has attracted attention. Specialist cladding contractor Schneider has broken technological boundaries to deliver the unique facade, using a tailor-made delivery system and installing it without tower cranes, instead using robotic arms.

Small, highly-trained teams, together with the bespoke manipulator robots were able to construct the building’s envelope at an astonishingly fast pace; one entire floor was clad in two days. Long lead in times allowed delivery and installation processes to be worked out in great detail avoiding the need to learn on site.

Vivien Phelps, package manager with main contractor Bovis Lend Lease, says: “We’ve pushed at the boundaries of both cladding installation and logistics on this project. Schneider has raised the bar.”

The 13-storey office development is part of Land Securities’ Bankside 123 development, a multi-million pound project that will bring around 65,000m2 of office space to Southwark Street, a busy thoroughfare that runs parallel to the South Bank. Both Bankside 2 and 3 are on site now.

The building takes its cabbie-friendly nickname from the facade, which is distinguished by strips of vertically-aligned blue fins, 2300 in all. Their design and installation is central to understanding why this fascinating project is so groundbreaking.

Touring the building’s exterior reveals detailing and finishes of the highest quality.

It’s as if the entire block has been precision-engineered and machine-tooled in a futuristic sculpture workshop. Interfaces between thresholds and junctions are flush, elevations are crisply defined, and its highly-textured surfaces sparkle in the sun. Did it land in Southwark fully formed? No, but it’s not too far from the truth.

Close collaboration

We’ve pushed at the boundaries of both cladding installation and logistics on this project

Vivian Phelps, Bovis

Bovis, architect Allies & Morrison and Schneider worked closely together from the start. Stephen Tanno, technical manager for Schneider GB, explains: “Allies & Morrison called us at the concept stage, they were looking for us to say whether their facade proposals were technically feasible, and whether it was cost-effective. We’re seeing this happen more and more. And for Land Securities, design is critical at the early stage; they believe in formalising an integrated team approach.”

Schneider did everything connected with the envelope: balustrades, internal timber cladding, unitised systems for the atria. “It was a complete approach,” says Tanno. “Nothing was left to be co-ordinated down the line. And it was on a GMP basis.”

Bankside 1’s elevations are composed of stacked curtain wall ’units’. Each of these building blocks comprises an aluminium structural profile, glazing, a gasket system, an acoustic element and a number of blue fins.

Three key factors determined the design and installation of the unitised system: the lack of available tower cranes, a desire to avoid a two-stage installation process, and rigorous health and safety concerns. Phelps says: “The cladding package has been driven in part by the requirements of the programme. Initially, we were going to install the fins separately, with external access, but time and money forced a change in logistics. We had a short programme and we couldn’t wait for the frame to finish before we started on the envelope.”

To work around these constraints, Schneider took a remarkable decision – to finance and build a prototype superstructure that would mimic on-site conditions. This was erected at Schneider’s Polish facility in Wroclaw in the summer of 2004, while cladding was due to begin in Southwark the following February.

Phelps says: “Schneider took elements of the structure, both typical and unique, and highlighted areas where there may be difficulties. For example, we have some columns quite close to the floorplate corner so they used the prototype to mock-up on this too.”

Bankside 1 has 16 different cladding unit packages which include: a typical unit; a first floor unit, which has no fins; a slightly larger second floor unit; a double-height plant unit; and internal atrium units. Scnheider tested each unit type in stages at Wroclaw.

No tower cranes meant using manipulators – robot arms mounted on driver-operated buggies – to install the units, which Schneider adapted to fit on-site conditions. Tanno elaborates: “It’s about utilising prefab to its full potential. At one point the operator was going to sit on the manipulator but it was suggested that if the driver was able to stand at the edge where the unit was being installed he’d have greater control. So we created a remote control panel that’s worn around the neck.”

The process of fitting the cladding units accurately required fine tuning. This meant that when the operator got to the slab edge he got off the machine and accurately positioned the top-hung units by remote control. This technique also meant that the edge protection could stay in place and that there was no need to harness the operators. Further adjustments were then made to satisfy Bovis’s health and safety requirements (see box below).

We never had more than 15 men on site at any time. On a project of this scale, that’s significant

Stephen Tanno, Schneider

Getting the units up into position was central to the project’s logistics. It meant having a dedicated zone – a clean safe environment with walls, a roof and concrete floors – for the sole use of Schneider. A gantry crane hung from a steel frame erected over the zone lifted the units from the lorries and laid them flat on tilting tables. The tables were then tilted to the vertical and hoisted to the first floor where they were then attached to guide rails to take them further up the structure. Manipulators on each floor then collected them and set about working their magic, first holding the units out over the slab edge and then, using spigot guides on the units already fitted on the floor below, placing them securely in position.

Polish testing

All the logistics regarding how the zone operates were first tested in Poland. Tanno says that because the team on site was fully trained, potential problems were avoided. “If the brackets have to be adjusted, we’ll do it in Poland,” he says. “If the manipulator needs attention, we’re adjusting that before we come to site. It allows us to hit the ground running.

It speeds up the on-site programme, it reduces the risk of something going wrong, and it means you have a technically trained workforce aware of all the health and safety issues as well. It’s become standard practice to us.

“Sometimes people ask: ‘why do you need such long lead in?’ Well, if you want this level of innovation and efficient working, you have to give up the time to develop and evolve your ideas.”

Tanno says the process of unloading, doing some sub-assembly work on site (rotating the fins into position, they were flatpacked for delivery), lifting the units on the outside of the building and then handling them with a manipulator on each floor plate, is totally unique. He adds: “It’s a semi automated process, keeping the manpower input to as little as possible. We never had more than 15 men on site at any time. On a project of this scale, that’s significant.”

It took two or three men to install a unit, with the time from ground to installed position taking around 40 minutes. Schneider installed around 12 units a day, 35 linear metres.

The same method has been slightly tweaked for Bankside 2 and 3. The units are terracotta clad, which are much heavier than aluminium fins, so the manipulators are more powerful. And column placement on the floor slab has meant installing systems around corners, testing the flexible robot arm, which can move and rotate in any plane, to the max.

Tanno claims Schneider has set a new benchmark for the company and the construction industry as a whole. “It’s actually made people sit up and take notice that you can develop work methods that are inherently safe, technically reliable and fast as well,” he says.

Tanno believes skyscrapers are the next challenge: “We’re adapting the system for high-rise buildings. We’re looking at projects in the pipeline that go up to 40 or 50 storeys. Again, it will be independent of a tower crane and will use semi-automated processes.”