Viñoly’s comeback performance

Rafael Viñoly is one of a select band of architects working in the UK whose radical designs force contractors to rethink the way buildings are put together. It is an admirable talent, as long as the designs on paper can be turned into workable buildings. Unfortunately, the twisting curves and golden cladding of Viñoly’s Colchester Arts Centre ultimately drew the project into budget overruns and crisis talks between client and contractor. It was due to be completed by spring this year, but remains stalled to this day.

So it’s doubly good news that, despite some delays and an inflated budget, the Uruguayan-born architect’s largest UK project to date has been successfully handed over to the client. The fit-out is under way, in preparation for a December opening.

Leicester Performing Arts Centre – now rechristened Curve – is a seriously ambitious project. The brief called for a state-of-the-art theatre that would transform the very concept of performance itself, and Viñoly responded with a radical structural design that hangs most of the building’s structure from the roof.

As at Colchester, Curve is an urban regeneration project funded by the local council. It is also a signature building, defined by its sweeping 20m-high, 120m-long louvred glass façade, which cantilevers over the adjacent road. The roof-hung façade was one of several technical challenges faced by main contractor Bovis Lend Lease.

‘If you wanted to take this building apart you’d have to work from the bottom up, not the top down,’ says Martyn Woodhouse, project manager at Bovis Lend Lease. ‘The way it’s constructed everything hangs, or floats, which from a construction point of view makes it far more difficult.’

Situated in a rundown part of the city where a pool hall and strip bar sit alongside empty Victorian factories, Curve fits within its context about as comfortably as a plate of caviar at a KFC. But this contrast perhaps reflects the council’s ambitions for the area, and Viñoly’s bold vision. Transparency and flexibility are the main principles behind the design, which responds to client Leicester City Council’s desire to reflect the cultural diversity of the local population.

End user Leicester Theatre Trust also wanted a building that would allow as much interaction with the public as possible. ‘They wanted an ‘inside-out’ theatre with everything stripped back to the bare bones so the public can see what’s going on,’ says Woodhouse. ‘It will encourage people to come in and walk around the theatre during the day to see its workings.’

Although several architects tendered for the job, the council’s interviewing panel was unanimous in selecting Viñoly’s concept. He wanted production, craft and technical components all exposed to public view, dissolving the distinction between production and performance.

The stage and two auditoria effectively sit on an island surrounded by a public foyer, removing the usual distinction between front and back of house. When large steel shutters surrounding the stage are raised, the public will get a view of stage preparations through the continuous glass façade at street level.

For Tony Stafford, project manager at Rafael Viñoly Architects (RVA) the transparency concept could work only if the structure was sufficiently stripped back. ‘It was vital that the brief came through in the design and the structure to bring the whole thing together,’ he says.

Rather than support the building on columns, which would have interrupted views inside theatre spaces, RVA proposed four huge concrete stair and lift cores located at the corners of the central performance area. These act like table legs, supporting a giant trussed roof structure, from which everything else is hung, including the façade, rehearsal and seminar rooms and the heavy equipment required for productions.

Everything hangs or floats, which makes it far more difficult

Martyn Woodhouse, Bovis

The façade drops to 5m above ground level, beneath which sheet glazing provides uninterrupted views. An internal mezzanine walkway above this level is cantilevered from the base of the façade’s columns, with additional support from steel rods suspended from the roof, allowing people to circulate within the building at first-floor level.

The façade surrounds the two concrete-enclosed auditoria – the purple one with 750 seats, and the smaller red drum housing 350 seats – which face one another across a central stage. The flexible interior design means the theatre space can be used as a single venue or as two performance areas, divided by specially designed shutters to prevent sound leakage.

‘It’s a simple design architecturally, the massing and volumes are all very straightforward, but to get it all hanging in space was a bit of a feat for the structural engineers,’ admits Stafford. ‘But it’s more than just the structure, it’s how the whole building comes together to allow continuous views through the theatre so everything on the inside is on show.’

Faced with such a technically challenging project, Woodhouse won’t be drawn into comparisons with Colchester Arts Centre, although he admits: ‘There has been a heavy reliance on the expertise of the trades to help develop the design into a working solution.’

While the client retained design responsibility for Curve under the JCT lump sum, two-stage contract, several difficult packages, including the building envelope, interfaces, façade, roof, M&E elements, lifts and piling, were taken on by the contractor.

Perhaps not surprisingly, Woodhouse also argues that a regional contractor like Banner Holdings was a less-than-ideal fit for a project like Colchester.

‘Here, we benefited from our knowledge of the upper end of the supply chain, which fed into our ideas,’ he says. ‘There was a lot more interaction than is typical on a standard project.’

RVA’s Stafford says that Colchester is perfectly buildable and that Curve is complicated but by no means exceptional. ‘It’s just forced a lot of people to think slightly differently to get it to work.’

Thinking differently was vital during the design stages as political changes at the council brought about several alterations. ‘We’ve had three different council leaders while I’ve been on the job, then the original leader came back in just as we were about to go to site,’ explains Woodhouse.

This inevitably introduced costs into the project, which combined with extra funds required to increase the specification of theatrical equipment, and costs associated with several delays, pushed the original £48.3m budget to £61.5m. Most of the funding came from Leicester City Council, supplemented by funds from Arts Council England, and £2.4m from the National Lottery.

Unlike a traditional build, on which several elements are worked on simultaneously, Curve’s unique structure meant everything had to be erected in a specific order devised by Bovis, its structural engineers Adams Kara Taylor and structural steelwork contractor William Hare. This partly explains why the project has taken so long – construction began in June 2005.

There has been a heavy reliance on the trades to develop a working solution

Martyn Woodhouse, Bovis

‘First we had to get the majority of the concrete and the lift and stair cores up before we could start work building the roof, and nothing could be hung until the roof was finished,’ says Woodhouse.

At its greatest extent, the roof cantilevers out 7m beyond the base of the building – and 10m from the nearest supporting core. So to ensure it could support the heavy façade, the roof was built using huge 5m-deep trusses with secondary beams spanning in between. This allows staff to walk around inside and access services and equipment.

The roof was erected in stages. First the cantilevered rear section over the smaller auditorium and foyer was built and supported on a temporary support. Next, concrete was poured for the roof slab over the stage. With this in place, the temporary support was removed, allowing the slab over the stage to act as a counterbalance to the cantilever over the small stage and foyer. Finally the roof over the larger auditorium was built.

Remarkably, the steel roof has no fixed connection to the building, a requirement because it’s so big it generates considerable thermal movement. Instead it sits on large sliding bearings attached to the concrete cores. Typically seen on bridges, these bearings allow the roof to slide in two directions independently of the concrete cores, allowing as much as 50mm-70mm movement.

The four concrete cores are separated from the concrete of the auditoria drums by an air gap to prevent noise transference through structure and into the theatre. And to prevent noise transmission from the plant rooms across the roof into the structure, acoustic pads are positioned between the cores and the roof.

Work to hang the façade’s steel columns from the roof began in February 2007. Thermal movement in the columns, which sit at 7m centres, was again a serious issue. The team had to work to 2mm of tolerance to accurately position each pane of glass between columns. However, surveys revealed that columns were moving up to 21mm in a day. With delays having an impact on the programme, AKT devised a temporary rigid bracing structure to stop the movement. Once the panes of glass were dropped in, their weight would stop the columns moving. The process was closely monitored to check movement against computer predictions, and compensations were made.

A pre-camber on the roof allowed the structure to drop as the glass was hung, gradually bringing the columns into tension. ‘We started on the most difficult bit with the furthest cantilever, and therefore the furthest element of movement,’ says Woodhouse. ‘It was a huge relief when we took the temporary bracing off and the glass didn’t crack.’

Viñoly himself appears to have been closely involved in work on site. ‘Certain things, like the façade, were very precious to him and any proposed design changes by the client had to be run past him first,’ says Woodhouse. ‘During the tender and first-stage development he was over here once a fortnight and his glass specialist, Charles Bloomberg, was down every two weeks for the first few months.’

Indeed, a strong dialogue between the client, contractor, sub-contractors, design team and structural engineers may be what helped steer this project away from the type of problems encountered at Colchester. Bovis typically met with the designers and subcontractors four to five weeks ahead of beginning any job on site. AKT even put together tutorials for contractors, explaining the particular challenges of the job at hand.

‘Although the project went through several design changes in the early stages, and it gave people a few sleepless nights and headaches, there was never any doubt that eventually we could make it work,’ concludes Stafford. cm