A dramatic fan-shaped roof, supported by cantilevered glulam beams, defines the new Warner Stand at Lord’s, constructed by BAM amid a busy schedule of international fixtures. Andrew Pring reports.
On 7 May, weather permitting, England will play Ireland in a 50-over game at Lord’s cricket ground and members of one of the most exclusive clubs in the world plus their guests will spend the day enjoying a superb view of proceedings from 2,656 very comfortable seats in the newly completed Warner Stand.
The project managers from BAM who spent 86 weeks building the new £22m stand are unlikely to be among them. Kevin Stoney will be busy on his new challenge, and his on-site boss Richard Pateman has other plans. But devotees will be grateful to them both for delivering a jewel of a building, elegant and striking and perfectly in keeping with its historic surroundings in what is often called the cathedral of cricket.
So will the client. The Marylebone Cricket Club (MCC) commissioned the stand as part of its 2013 masterplan for upgrading the ground’s facilities, and knows full well the sensitivities involved in making any changes at the world’s most famous cricket ground.
Client Marylebone Cricket Club
Structural engineer Arup
Services engineer Arup
QS Gardiner & Theobold
Project management Gardiner & Theobold
Planning consultant DP9
As a longstanding member of the British establishment, the MCC has a fusty image in many cricket-lovers’ eyes. But when it comes to architectural enhancements at the ground where it has been headquartered since 1814, the club has displayed a truly adventurous side.
The Stirling Prize-winning 1999 Media Centre, with its sci-fi semi-monocoque design from Future Systems, seemed initially an aberration to many traditionalists but now looks as comfortably at home as the grand, Grade-II listed Victorian pavilion facing it. And Hopkins Architects’ quirkily tented roof on the refurbished Mound Stand in 1989 quickly found its way into Pevsner’s Buildings of England series.
The new Warner Stand looks nowhere near as futuristic as the Media Centre (which has also been refurbished, see p36) but with its glorious fan-like roof, supported by 11 cantilevered American white oak glulam beams ranging in length from 18 to 24m, it’s just as likely to attract architectural garlands.
Spectators will certainly be delighted. Poor sightlines in the old Warner Stand deprived 600 seats of a full view of play – the new rake reduces this to 30-odd. Full views for all would be impossible in anything other than a circular stadium.
The former stand was deficient in other ways. Built in 1958, it had no lifts and only two entrance points. On a Test day, it could take 22 minutes to exit. More worryingly, the ICC, cricket’s international governing body, described the match-control and officials’ facilities as the second worst in world cricket. When every other Test stadium in England had upgraded, the MCC was in danger of losing the right to stage Test matches.
A masterplan for redevelopment of the whole ground was commissioned from Populous. Leading the project was senior principal Philip Johnson, who had previously led on the London 2012 Olympics stadium. The £200m masterplan aimed to upgrade facilities throughout and envisaged the phased replacement of five stands – the Warner first, followed by the Tavern, Allen and the Compton and Edrich stands – to increase capacity from 28,000 to 32,000.
American white oak beams are craned into position
Populous was commissioned to design the new stand in 2013 and spent several years developing its design, working closely with Arup. Alert to the potential objections of the well-heeled denizens of St John’s Wood, it employed a planning consultant. Planning consent was granted in 2014 and BAM won the D&B contract, tendering when the design reached Stage E. Populous and Arup helped BAM develop the designs and were then novated to the contractor, with teams from both retained by the client.
The teams were quite well acquainted. Populous, Arup and BAM had worked together on the Leeds Arena stadium as well as another D&B project. And the designer, engineer and contractor have longstanding relationships with the MCC: Populous has been offering strategic planning advice since 2005; Arup was part of the team that built the Mound Stand (1986), the Compton and Edrich stands (1991), the Grand Stand (1998) and the Media Centre (1999); and BAM built the Mound (an employee on that project is on site now).
BAM was to start at the end of the 2014 season but, with the Australians touring in 2015, the MCC decided to push this back to the next year. Says Pateman: “It gave us the opportunity to develop the design before we started, which helped us later on in the construction process, particularly with the delays at the front end.” Of which, more later.
The new stand is designed as a reinforced concrete frame that two precast terraces slot on to, all sitting on a 4.5m deep basement. Its front half of the stand is precast, the rear half is an in-situ concrete frame, with the precast beams on top of and cast into the in-situ frame.
Exploded view of stand
It has four levels: the lower floor, housing the plantroom and a state-of-the-art match control suite for officials; two terraces of seating; and the fourth floor containing a 135-cover restaurant for use throughout the year. The seating follows the bowl of the stadium on the lower tier, curving more directly to face the pitch on the upper level. Much stress, says Johnson, was placed on “finding the sweet spot between viewing and comfort, and access and circulation”.
Each terrace has four entrances, and there are three staircases, two passenger lifts and one goods lift. The section of the stand facing nearby houses is green-walled, and solar thermal and PV roof panels generate hot water and electricity. Windows facing the residents are obscured to prevent over-viewing.
The project was split into two phases: the first, which began in August at the end of the 2015 cricket season, was to take 41 weeks. At that stage the basement and the two terraces – minus the roof – would be finished and ready to accommodate spectators for 2016’s test matches against Sri Lanka in June and Pakistan in July, plus county games until the end of the season. After this, phase two would commence, taking 32 weeks to hand over at the end of April 2017.
The already tight schedule was severely tested when asbestos was discovered during demolition of the old stand at the start of the onsite work. BAM’s Pateman explains: “We found asbestos when we started the demolition in the terracing area of the stand.
There were elements of boarding that had been used as soffit supports for concrete that weren’t visible when the client did their original survey. It was built within the structure – so you couldn’t see the difference between it and concrete. They knew there was asbestos in other parts of the building but they’d never identified this section.
He adds: “Fortunately for us, the client had undertaken the demolition survey, so they took the risk. They’d got a saving by doing that. Had they asked us to price the risk, we’d have had a slightly longer programme.”
Dealing with the unexpected asbestos took five weeks, and demolition was halted until it had been removed. Pateman says: “We had to get our subcontractors to readjust site times, but we gave them sufficient notice to do that, and the client paid some additional money towards the reprogramming.”
The new Warner Stand features the longest cantilvers ever attempted with glulam American white oak
Despite this, no time was lost. “It was very impressive that the subcontractors pulled it off,” says Stoney. What was lost, however, was seating in the stand for the Sri Lanka game – the MCC instead arranged temporary seating in front. But come the Pakistan game in July, every new seat was ready for a thrilling game.
BAM met a further unforeseen challenge with boreholes for the open-loop cooling and heating system, which Arup designed to deliver a 100% electric building for its sustainability-aware client. BAM project manager Stoney explains: “We dug one borehole at the far end of the estate, in the Nursery area, and one near the new stand.
They’re 214m apart and go down 100m into the aquifer. Water is drawn out of the aquifer at one end and put back in to the aquifer at the other, generating heating and cooling simultaneously using an innovative heat pump system delivered by Dutch specialist Groenholland.
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“We had some issues with the discharge into the system – we were extracting water at a certain rate from one borehole and then trying to pump it back at the same rate, but something was preventing that happening. We discovered that there were sand layers between the chalk and that this had to led to a collapse at the bottom of one of the boreholes at the Warner Stand end.”
He adds: “We had to redesign the system so it could work with a lower return flow rate, and agreed with the authorities that at peak demand, which was 20 days a year, some of the ground source water would go to drainage rather back down the borehole. We remediated one of the boreholes and added some drainage at its base of the borehole, and the problem was solved.”
BAM decided to split the building into two sections once the project was up and running. Pateman says: “We did the in-situ work using a tower crane, and then we started to load on the precast, so we could work on two different fronts. This helped speed the programme, particularly when we were making up after the delay. Once we got past the second floor, we could actually start the process of lifting the individual precast units on to this lower level of the interbracing while we carried on with the frame at the back.”
The precast terraces slot on to a concrete frame
The 18 tonne precast elements and the glulam beams had to be transported across the outfield then lifted into position with a 200 ton mobile crane. BAM was allowed to put a trackway down on field side for only three days so as not to overstress the sacred turf. Even so, it was replaced later by ground staff, using turf grown at a specialist farm for over a year, to match the rest of the precious sward.
BAM used continuous flight augur piling for the foundations and silent sheet piling for the basement box, rather than noisier methods that would have raised tensions with residents. Another advantage of sheet piling was that less material had to be removed from the site.
Connecting the roof beams
If the asbestos and boreholes were unanticipated challenges, setting the new roof beams in place was seen from the start as the biggest test. The precast concrete beams had to be slid between the in-situ and precast structures, then connected horizontally and vertically with reinforcement bars. The tolerances were very small and the BAM team had to calculate how much the structure would deflect under the weight of the beams.
“You’re aiming for a level that’s slightly higher than its final position as you know it will drop down a bit,” explains Stoney. “Arup gave some guidance as to theoretically what you would expect but the structure never quite performs as the model says it’s going to. So we did the theory, sat down with the specialist and took a view on it. We knew concrete of this size and bulk was not going to deflect 30mm over that length – it might be 5-10mm – and Arup’s engineer was with us as we measured it and we guided them all in successfully.”
“We wanted timber for the beams because the client is very keen on sustainability and, although they are the longest cantilevers attempted with glulam oak, we are architects who like to push boundaries.”
Philip Johnson, Populous
The glulam beams are made of American white oak – the Warner’s cantilevers are the longest to use this material. Populous’s Johnson worked with Arup’s engineers (led by William Whitby) in selecting the oak. He says: “We wanted timber for the beams because the client is very keen on sustainability and, although they are the longest cantilevers attempted with glulam oak, we are architects who like to push boundaries. Arup has specialists in this area, and they found the stiffest product we could use. We felt confident we could make it work.”
The wood had to be shipped from the USA to Germany first, to the Bavarian factory of Hess Timber, to be prepared. As it was so hard, it was difficult to get the glues to bond, and the surfaces had to be sanded manually. The wood was then so dense that the x-ray checking machine was unable to perform its task – so every aspect of the beam had to be inspected visually. Rigorous testing in Germany was followed by a similar process to get Building Control approval in England.
Creating the roof was “the biggest challenge”, says Whitby: “When you’re in the restaurant, you don’t want to feel as you though you’re enclosed in an internal space, away from the cricket – so we wanted it to be highly insulated but also appear as though it was outside.”
It was complicated, too, by the architect wanting visual continuity between the roof of the restaurant internally and that over the seats externally. The answer was found in a translucent white tensile fabric called PTFE (polytetrafluoroethylene – the chemical name for Teflon), a woven glass-fibre cloth coated with PTFE polymer.
Internally, above the restaurant and other internal areas, the fabric is a sandwich of two layers of PTFE-coated woven glass-fibre cloth, with an aerogel-impregnated fleece between, providing the insulation to meet Building Regulation standards for a roof over a heated and cooled space. Both forms of fabric are translucent, and look identical to the untrained eye. This makes the roof appear to float over the accommodation and seating below.
Populous had used the glass-fibre cloth at Ascot Racecourse, but the fleece had not been used in Europe before, and BRE certification had to be obtained. Before proceeding, Arup invited the client to its London sound laboratory, where it replicated the roof environment, to the extent of simulating rainfall on its surface. Up to achieving compliance, the whole process took eight months.
View from Coronation Garden
The European division of Taiyo handled installation, as well as placement of the glulam beams and all the steelwork. Other specialists were Fleetwood, handling the envelope, and Creagh, which supplied the precast lower terraces and cantilevers on the upper terraces. The groundworks and precast basement were by GCL.
In the final few weeks before handover, Pateman and Stoney reflect that “however many jobs we’ve done, we always learn something new each time”. They say this project is by no means their most complicated – the Morgan Stanley Clinical Building at Great Ormond Street Hospital in 2012 takes that accolade – but “the technical details of the structure were just as challenging”.
Understanding the needs of the client, they admit, was also a challenge. Says Stoney: “Part of any construction process is trying to understand what your client wants to achieve. Here, everything is about cricket and it took us a while to deal with all the user constraints that placed on us.”
This included making sure Coronation Garden to the back, famous for picnicking spectators, was available for the Tests. He adds: “Lord’s is a large and multi-headed organisation, and we had to deal with many departments, trying to explain to them the challenges and constraints of our processes.”
With the stand due to complete on time and to budget, BAM clearly handled the diplomatic manoeuvrings as well as the construction. And it has fulfilled the architect’s aspirations too. Johnson says: “The construction quality looks very good, and the different materials have come together really well, particularly the timber and the steel. And it fits into the ground well. For all the 3D modelling you do, that’s something you can never be sure of until you actually see it finished on site.
“Lord’s is very special, with so many different places in the ground offering different experiences. There’s a perception that architects are only interested in what things look like but that’s not right – the experience of being there is just as important. This stand adds to the Lord’s tradition.