J-DRain GRS50 consists of an impermeable polymeric sheet cuspated under heat and pressure to form a high flow dimpled drainage core. The core is perforated, then bonded to top root resistant filter fabric and bottom protection fabric, specifically designed for Greenroof applications. The top root resistant filter fabric prevents roots from affecting the efficiency of the drainage/aeration layer and retains soil or other fine particles from being washed away and allows water to pass into the drainage core. The bottom protection fabric safeguards the waterproofing membrane.The core is installed dimple side down to allow water retention. The excess water is collected and conveyed to a proper collection system.