Architect: Mark Craine

Brett Martin

Very good fit for purpose, good design and courageous use of space

Located in Queen Elizabeth Olympic Park, the iconic London Olympic Stadium is being redeveloped for London Legacy Development Corporation. The Stadium is due to open in October 2015 to host the Rugby World Cup. The stadium will be home to West Ham United Football Club as well as the new national centre for athletics. The project features a 44,000m² roof, which at a depth of 84m is the longest cantilevered roof of its type in the world. The new roof is twice the size of the original and covers every seat in the Stadium, improving acoustics and the spectator experience. The original roof covered only 40% of spectators. Doubling the size of the original roof has been a significant challenge. Providing enough support for a new roof of this size required substantial strengthening work to the main roof trusses with substantial cost implications. A primary design consideration in this project was the incorporation of a light weight yet robust and resilient roofing material which would offset the amount of steel required. A further design consideration was that the material would offer the necessary versatility and workability to allow it to be configured to fit the complex concentric roof structure and unusual purlin alignment. Possessing the necessary strength to weight ratio, impact resistance, for long term weatherability, ease of workability, fire performance and over 90% light transmission, Brett Martin’s polycarbonate sheets used in this project made the architectural vision a reality. These unique material properties inherent in PC sheets have enabled the stadium designers to achieve a roof structure which simply would not have been possible at this scale otherwise. The cantilevered roof is made up of 21,862m² of polycarbonate, a total of 4,484 individual PC roofing sheets, which contribute to a mere 2% of the weight of the overall roof structure. Over 60% of the polycarbonate sheets have been cut to shape to fit the structure. The roof is made up of two sections running concentrically around the stadium. The rear section is covered with a single ply membrane and the front, more steeply pitched section, comprises PC sheets. Over 4,484 sheets of polycarbonate have been used to form this front section of the roof canopy covering an area of 21,862m². 2mm thick, special width PC sheet material was supplied to achieve specific spanning requirements. 38% of the PC sheets required for the project had to be to be individually taper cut to fit the intricate concentric roof structure. A total of 2,756 sheets required tapers to one or both ends and often along the length of the sheet to ensure end laps would align with the purlins. Working from the same 3D model created to generate the steelwork, Brett Martin devised a detailed Cutting Plan for the project which would translate on site. It comprised an identification system to relate each cut sheet to its position on the roof. As a result of the complexity of cutting, time constraints and health and safety implications, the cutting could not be achieved on-site. A dedicated production cell with specialist equipment and task force was set up at Brett Martin’s polycarbonate extrusion facility in Co. Antrim. In addition, project specific QC software was developed to allow the manufacture of so many bespoke sheets. This production cell was responsible for the individual cutting of 5,056 taper cuts with a mix of 1, 2 or 3 cuts per sheet. Production and delivery was phased for the 56 individual bays throughout the 12 week period of the installation with each sheet individually labelled according to its position on the roof. The subsequent installation has been achieved within the project timeframe and has resulted in a roof structure which is now part of the iconic sky line of the City of London.