A mono-component liquid applied roof waterproofing kit based on polyurethane. It consists of polyurethane resins, is elastomeric, and has no reinforcing mesh internal layer (only needed in singular points; evacuations, upstands…). The kit, once polymerized, conforms an elastic lining, in form of a layer completely bonded to the support. The minimum layer thickness of the assembled membrane has to be 1,2 mm.