A liquid applied roof waterproofing kit based on polyurethane. It is constituted by polyurethane resins, is bi-component and elastomeric, without a 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 1,5 mm.