Prefabricated modified polymerbitumen membrane whose compound is composed of distilled bitumen and elasto-plastomers (APP) reinforced with a perforated fiberglass mat. Both sides of the membrane are protected by a polyethylene burn off film. The diameter of the holes are of 40 mm and evenly across the surface. In virtue of the particular formulation, the POLYFOR membrane is compatible with both SBS and APP membranes manufactured by NORD BITUMI. POLYFOR is used for partially bonded waterproofing systems and applications, providing for a constant, evenly spread and homogeneous bond to the substrate. The application of POLYFOR allows for vapor to travel freely below the waterproofing layer allowing for it to be expelled through suitable air vents.