High-performance, CE-marked drainage system with a water reservoir for roofs with limited fall that are planted with extensive or intensive vegetation, or where extensive drainage lengths are required. The drainage system prevents the build-up of hydrostatic pressure on the waterproofing membrane, protects it against mechanical loads and ensures that vapour is able to evaporate freely from the XPS insulation on an inverted roof. It's a 3-in-1 product (on roll) consisting of a filter geotextile and a vapour-permeable geotextile that are glued (not thermally bonded) to the dimpled core.