PURPOSE: A water-stopping sheet excellent in properties such as heat resistance, weather resistance, and ground followability, and applicability, comprising a so- called low-density, linear polyethylene prepared by copolymerizing ethylene with a 4C or higher α-olefin.

CONSTITUTION: A sheet about 0.8W1.6mm thick is formed by melt-extruding an ethylene/4C or higher α-olefin copolymer (density of 0.91W0.94g/cm3, m.p. of 110W130°C, and preferably melt index at 190°C of 0.1W20g/10min), e.g., ethylene/ 4-methyl-1-pentene copolymer, at about 200°C through, for example, a T die. This sheet is used as a water-stopping sheet. The above sheet has many excellent properties and can pass well the technical standard for class 1 synthetic polymeric roofing sheets as regulated in JISA-6008 (1973). Bonding between sheets can be carried out easily by a hot melt method.