A drainage system having an at least 2.5 mm thick bi-planar mesh structure drainage core and a filter material against one face and a filter material or impervious member against the other face. The drainage core has generally parallel main strands interconnected by generally parallel subsidiary strands....http://www.google.es/patents/US4815892?utm_source=gb-gplus-sharePatente US4815892 - Drainage material and drainage core for a drainage system
Drainage material and drainage core for a drainage system
