Approx. 80% of the floor slab was carried out with steel fibre reinforced concrete according to performance class. The calculation was made by Schulz-Concrete-Engineering. Here, a performance class of 1,2/0,9 was determined. Since the floor slab had to take a load-bearing function because of the high loads of the „Piektowers“, a concrete according to performance classes was stringently required. In 2010 the concrete supplier has already successfully carried out performance class tests, so that the concrete could be delivered without any problems and further tests according to performance class. The concrete sections were carried out without any joints.