According to general regulations for roofs with waterproofing, flat roofs should have a fall of at least 2%. Pitched roofs start with a slope of 10° (18%). From 10° on, the green roof system build-up differs significantly from system build-ups below 10°. Shear forces increase with the roof slope and have to be transferred into stable beams. The substrate layer has to be protected against erosion. Plant selection and planting methods are to be adjusted to the relevant slope and exposure.