To provide a secondary water stop structure of a waterproof sheet roof, reducing the risk of water leakage.

A plurality of sheathing roof founds 1 formed of a folding board are installed with the groove longitudinal direction along the water gradient. The lower end of the sheathing roof found 1 at the most under water side is laid along the outer wall surface of an outer wall 2 such as a parapet raised from the roof surface. A heat insulating material 3 and a waterproof sheet 4 are laid on the sheathing roof found 1. A drain lateral gutter 12 for secondary water stop, which receives water flowing down from the sheathing roof found 1 is provided along between the lower end of the sheathing roof found 1 at the most under water side and the outer wall surface.

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