Green roof is an environment-friendly structure developed globally as a result of increasing urbanization. In this review paper we first tried to collect classification, structure and materials of green roofs. Increasing water availability of substrate using water retention additives is also collected and studied in this paper. Accordingly, different materials are applied in green roofs, among which polymers have attracted a lot of attention. Polymer materials are widely used in different layers of green roofs due to their characteristics like light weight, which is an important concern about green roofs. So, in the next step, we gathered different polymeric materials that are used in different layers of green roof or can be used in this structure. For example, low density polyethylene (LDPE) or polyethylene (PP) material use as physical barriers. Therefore, this article provides an opportunity to review and compare different polymeric materials that have been studied in different articles in various layers.