Most modern green roofs (a common exception is traditional Scandinavian turf roofs) are built on top of conventional compact roofs. At the very surface, various plants grow in a growth medium. Below lies a layer for water storage and drainage. Erlend Andenæs will in his PhD project thoroughly assess the various building-related challenges and risks associated with green, blue-green and blue-grey roof solutions. Read more about the project here and in the technical article from Byggeindustrien (in Norwegian).