The larger insulating material thicknesses, the demands on the aesthetics of a flat roof structure and larger spans have led to the development of the fully insulated, prefabricated Multibox element as a flat roof. Due to the arrangement of the load-bearing wooden elements between the vapor barrier and the roof skin without a rear ventilation level, the construction is not unproblematic from a building physics point of view. In addition, the number of cases of damage to such constructions has...