For unused and extensively landscaped flat roofs, DIN 18531-1 distinguishes between two design qualities:
Application class K1: Roof waterproofing to which usual requirements are placed (standard requirement). Roofs of application class K1 should have a minimum slope of 2% and can also be planned without a slope, provided that the waterproofing meets the requirements of application class K2.
Application class K2: Roof waterproofing with increased requirements, e.g. for higher-quality building use, high-rise buildings, roofs with technical systems such as solar systems and/or hard-to-reach roofs. A minimum gradient of 2% is to be planned in the area, throats should have a minimum gradient of 1%. In addition, there are other requirements and design details that go beyond the requirements of application class K1 and are intended to ensure a longer service life, increased reliability and/or lower maintenance costs, e.g. different connections and fastenings, a mandatory multi-layer system structure (for waterproofing with bitumen/polymer bitumen membranes) and other building materials.
Source: bauwion
