Abstract: A polymeric waterproofing membrane is provided which has an improved biaxial elongation compared with conventional polymeric waterproofing membranes. The membrane is a composite of an upper layer and a lower layer as well as an in between situated barrier layer, wherein the barrier layer comprises at least one organic polymeric material and the upper layer and the lower layer comprise at least one organic polymeric material which has better mechanical characteristics in comparison to the organic polymeric material used in the barrier layer. The upper layer and the lower layer contain the same or different materials. The organic polymeric material for the barrier layer is not damaged upon biaxial elongation of the polymeric waterproofing membrane, and biaxial elongation of the polymeric waterproofing membrane does not result in separation of the layers.