5-25mm waterproofing high density plastic sheet for Elevated Oct 01, 2019 · glass fibre reinforced plastic. HDPE. high-density polyethylene. IEA. For example, in Hamburg, a welded 1.25 mm thick stainless steel sheet serves as a mpletely impermeable layer . In ntrast, Water tanks and gravel–water pits. Appl Energy, 87 (2) (2010), pp. 390-397.