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Aquatic spectacular

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Stephen Cousins

Relieved of its controversial wings, Zaha Hadid’s Aquatics Centre has broken free as the cresting wave it was always meant to be

Aquatic Centre in Games mode.
Aquatic Centre in Games mode. Credit: Hufton + Crow

It is only now, some 18 months after the London 2012 Olympic Games ended, that the Park’s most show stopping architectural attraction has been revealed. The billowing wave-shaped roof of the London Aquatics Centre, spanning some 120m and held up by just three concrete supports, is a true feat of engineering, which ­remained largely concealed during the Games due to the presence of the two box-shaped spectator stands clamped to either side.

These have now been replaced, as part of the building’s comprehensive transformation into legacy mode, by two huge faceted curving glass facades which flood the interior with light and give the impression that the dipping and diving roof hangs in mid air.

This ‘floating’ effect is enhanced by the thin self-supporting frames of the facades, made up of trussed steel alloy columns and slim-section transoms and mullions, which cantilever at a 15 degree incline and have no permanent physical connection to the roof. 

‘The glazed walls were critical to our concept for the legacy transformation,’ explains Jim Heverin, director at Zaha Hadid Architects (ZHA). ‘We wanted an immense amount of daylight in the pools to give people the impression they are swimming outside, or in a pavilion in a park. Importantly, the Aquatics Centre’s main focus is no longer as a venue, so the architecture had to become more transparent and encourage people to come in and swim. There’s very little use of local community sports facilities in East London, so the glass was key to creating an attractive and open building to ensure people don’t feel intimidated by this type of space.’

The Aquatics Centre reopened to the public on March 1, giving visitors the chance to experience the thrill of leaping from an Olympic diving board or swim in the pool used by the athletes for just £4.50 a ticket.

The transformation began at the end of last year when the stands on the east and west elevations were peeled back to reduce the building’s seating capacity from 17,500 to 2,500 and make way for 628 panes of double-glazed laminated glass – 314 on each side. The two facades, supplied and installed by Austrian contractor Seele, are conical in shape and cover a total area of 2,800m².

Clever detailing at the glazed wall/roof soffit interface gives the impression that the glass meets the roof seamlessly.
Clever detailing at the glazed wall/roof soffit interface gives the impression that the glass meets the roof seamlessly. Credit: Hufton + Crow

The glass walls had to accommodate movements in the roof, which is similar in design to a bridge and stands on giant bearings that allow it to slide. This creates huge dead load deflections of between 285mm and 435mm which are resolved using a clever 3D joint concealed in a box within the shadow gap at ceiling level. The joint is fixed separately to the facade and roof, and allows the roof to move in two directions. Flexible ­insulation completes the thermal envelope.

‘Due to the amount of movement in the roof, we knew that support for the glass ­facade itself would have to come from the deck, located behind the permanent seating,’ says Heverin. ‘Although ZHA isn’t known for expressive structure, a series of cantilevered steel truss columns, spaced at 6m intervals, provide enough support for the 74,235kg of glass in each facade, as well as wind loading, while increasing transparency compared to conventional solid steel columns.’

The columns stand on large steel base plates, needed to support the sheer length and weight of the cantilever. Inclining the ­facades means that they meet the roof well back from its edge, which has the effect of blurring the edges of the building and ­enhancing the sense that the interior swimming pool space connects to the outside. A drainage trench runs along the outside of the facades and a heating trench on the inside.

ZHA spent a long time rationalising the facade design. Initial plans which introduced movement into the facade itself were rejected in favour of a more straightforward infill design that would not compete with the roof for attention. The simpler design allowed the team to drive efficiency into manufacture by increasing the repetition of glazing panels, which was considered key to making the legacy scheme stack up financially.

Although most glazing panels are identical in size – around 1.5m by 3m – variations were required at the tops of the facades to adapt to the more complex curving roof  geo­metry. Top panels are smaller and partially concealed inside the deep shadow gap in the timber ceiling to give the impression that the roof directly butts up against the glazing. 

The complexity of the roof form required bespoke detailing where the glazing met the soffit.
The complexity of the roof form required bespoke detailing where the glazing met the soffit. Credit: Hufton + Crow

In legacy configuration, the Aquatics Centre is a BREEAM Excellent project. The facade panels’ U value of 1.4 W/m²/°C is low compared to regular double glazed units, and their air permeability value is no more than 5m3/hr/m2. ‘The sheer size of the space means it experiences a lot of solar gain, which to an extent balances out thermal heat loss through the facades,’ says Heverin.

A closed circuit radiator system in the trussed framework, developed by Seele and based on ZHA’s initial concept, circulates hot water to create a constant temperature across the surface of the glazing, reducing the risk of condensation and down draught.

In addition, the glass panels feature a screen-printed dot matrix pattern, which varies in across each elevation, to help control daylight levels and restrict potential glare, particularly around the diving boards. The pattern is invisible externally and can only be seen from the pools close up.

The new south facade in legacy mode is as elegant as its Games mode predecessor was clumsy.
The new south facade in legacy mode is as elegant as its Games mode predecessor was clumsy. Credit: Hufton + Crow

ZHA was criticised in the run-up to the Olympics for the box-like design of the temporary seating stands, but without the unique phasing between Games and legacy modes the spectacular glazed facades and soaring roof on show today would ­never have been possible, explains Heverin: ‘Games mode required a completely column free space to enable uninterrupted views from the spectator stands. This gave us the opportunity in legacy mode to emphasise the roof as spanning the entire site. If you were designing a swimming pool from scratch you would simply use columns to support the roof, but that wasn’t an option here.’

The finished building is hard to fault. The facades have an precision engineered beauty that is reminiscent of Joseph Paxton’s ­Crystal Palace or William Barlow’s train shed roof at St Pancras; their clean horizontal lines in dynamic tension with the dramatic sculpted roof above. 

Design Zaha Hadid Architects
Sports architect S+P Architects
Structural engineer Ove Arup & Partners
Services Ove Arup & Partners
Fire Safety Arup Fire
Acoustics Arup Acoustics
Facade engineer Robert-Jan Van Santen Associates
Lighting design Arup Lighting
Maintenance access Reef 
Security consultant Arup Security
AV + IT consultant Mark Johnson Consultants
Access consultant Access Design
CDM co-ordinator Total CDM Solutions
BREEAM consultant Southfacing
Quantity surveyor and project manager CLM
Main contractor Balfour Beatty (UK)
Facade contractor Seele 
Glass supplier Tvitec
Timber sub-contractor Finnforest Merk GmbH
Concrete sub-contractor Morrisroe

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