After a complete overhaul, the Bay Arena - the home of Bundesliga soccer team Bayer 04 Leverkusen - reopened itsgates in time for the start of thenew season, and now complieswith the very latest international standards. Thanks to the "home advantage”, BayerMaterialScience obviously played a significant role in this. The discus-shaped, translucent roof with a diameter of 217 m is a new and spectacular showpiece project for the application of Makrolon polycarbonate triple-wall sheets. With a total area of 28,000 sqm, the roof spans the stadium's entire extended stand area. Its construction is based on the spoked wheel principle. The design and subsequent assembly of the sheets presented a major challenge, because the circular external contours of the roof gradually change to a rectangular shape towards the inside. This means,simply because of the very large area involved, that enormous forces act on the roof. Another handicap was that very little time was available foractually putting up the roof. But polycarbonate has two great advantages: its outstanding machinability and the very low weight of the individual sheets. After preliminary assembly, the sheets were hoisted up by cranes to a height of 30 m,where they were mounted on the unsupported steel cable structure by specially trained industrial climbers.