German Parliament Building
In April 1999 the German federal government took possession of its new home: the Reichstag in Berlin, the German parliamentary building. On the roof, a lot of very different additional demands had to be taken into consideration over and beyond the requirement for 'normal' watertightness. As the roof is a terrace one can walk on it has to be mechanically able of supporting strong loads and also live up to the increased demands as regards its visual attractiveness. Besides the public, the heavy cleaning machines necessary for the glass dome as planned by the star architect Sir Norman Foster also constitute heavy loads. And finally, the roof area is penetrated at numerous points. This is why only roof strips with proven longevity are used. The choice fell upon a PYE sealing system, cellular glass insulation for slopes, a first layer of polymer bitumen welding strip (PYE) and as a top sealing layer a high polymer sealing strip.
These roof and sealing strips are plastic strips which have been softened with polyester, are open to steam diffusion and compatible with bitumen. The required security against seepage (bond between polymer bitumen strip and sealing strip) of the PYE sealing system can also be backed up by a test report written by the southern German plastics centre SKZ. In its tests - water stress with a pressure of 6 bar after previous perforation with 25 mm hole diameter and a test duration of 1,000 hours - the SKZ was able to ascertain neither any inflow of water nor a separation of the layers.