Prefabricated modified polymer bitumen membrane composed of polyolefin thermoplastic stereospecific polymers with high molecular weight and special distilled bitumens, with excellent characteristics of resistance to ageing and phase inversion (type APP). These built in elements, integrating themselves, enhance the excellent qualities of flexibility, lightness, adhesion, resistance to ageing and to UV rays of the GRID BIT P+V VIADUCT membrane. GRID BIT P+V VIADUCT is specifically designed to be used for bridges, viaducts, parking decks, roof gardens and for all those applications where very high mechanical resistance and excellent adhesion to the substrate are required. Dual reinforcement with a heavy weight woven non woven single strand polyester and rot proof fiber glass mat, which confer to the product high mechanical characteristics and excellent dimensional stability and static & dynamic puncture resistance. The GRID BIT P+V VIADUCT membrane is finished on the upper face with a special talc. On the application face, the membrane is finished with a woven non woven polypropylene mat.