PROBLEM TO BE SOLVED: To provide a construction method which can effectively prevent warping of a heat insulating layer made of a formed polystyrene extrusion foam board even when construction is performed in a hot time such as summertime, and which enables the inexpensive construction of a rooftop heat-insulation and waterproof structure.SOLUTION: In a construction method for a rooftop heat-insulation and waterproof structure 10, a heat insulating layer 3 is formed by laying an extrusion foam board, which has polystyrene used as a base resin, on a roof concrete slab 1, and a presser concrete layer 5 is formed above the heat insulating layer 3 with an insulation sheet 4 interposed between the two layers. A sheet with a brightness (L*) of 70 or more is used as the insulation sheet 4.
