Many types of waterproofing are compatible with green roofs. We like single ply roofing systems that are like pond liners making the roof one giant, shallow, planter. World-wide, polyvinyl chloride (PVC) and polymer modified bituminous membranes are the most common. Many of these installations have now been in place for over 30 years and continue to perform as designed. PVC, EPDM and thermal polyolefin (TPO) are, in most cases, inherently root-resistant; other common waterproofing materials require a root barrier between the waterproofing materials and the vegetated cover.