WATERPROOF METHOD OF FLOOR FACE AND WATERPROOF SHEET

PROBLEM TO BE SOLVED: To shorten a construction period of time by considerably reducing field work while securing a stable quality.SOLUTION: This waterproof method of a floor face comprises (a) previously forming a waterproof sheet 10A in a factory and the like, which includes three layers of a top coat layer 30, a waterproof layer 31 of high-quality urethane and a waterproof layer 32 of general urethane. Each of edges 30a, 31a and 32a are arranged so as to be substantially coincide with one another at the four peripheral sides of the waterproof sheet 10A. In a construction site, the method comprises: forming a primer layer 41 and an adhesive layer 43 on a roof floor face by using a usual method; then laying the previously-formed waterproof sheets 10A and 10A, in a position except a drain ditch, a rise part and the like without forming a gap between adjacent waterproof sheets; and applying an urethane waterproof agent on a ditch for drainage and the like to form a waterproof layer at the site. Waterproof sheets 10B and 10C may be used as a waterproof sheet 10 without forming the waterproof layer 32 of general urethane and the top coat layer 30.