The invention relates to a flexible barrier membrane (1) comprising at least one first layer (2a) of polyurethane, and at least one second layer (20) of material(s), which is incorporated into the first layer (2a) of polyurethane by a modification of at least one surface of the at least one layer of polyurethane. The at least one material of the at least one second layer is selected from the materials including inorganic silicon oxide, organic silicon oxide and a barrier polymer. The invention also relates to a method for producing the flexible barrier membrane (1).
