Synthetic waterproofing membrane obtained by coextrusion of a polypropylene elastomerised polyolefin (FPA =Flexible Polypropylene Alloy), with special non-toxic substances which give the finished product specific fire resistance characteristics, resistant to ultraviolet rays, reinforced by a composite reinforcement in polyester / glass fibers which makes it dimensionally stable. The membrane is made with contrasting colors between the upper and lower sides (signal layer) to allow visual control of the surface integrity of the same during and after the laying phase. Available in the color White Reflecta, with highreflectance, with SRI = 102%.