Water leakage preventing structure for roof parapet wall and construction method thereof

The invention discloses a water leakage preventing structure for a roof parapet wall and a construction method thereof. The water leakage preventing structure comprises a C20 plain concrete flashing poured on a roof external edge beam and a waterproof layer laid on roof floor slabs; a plurality of evenly-distributed expansion joints are formed in the C20 plain concrete flashing; round corners arearranged at the junctions of the C20 plain concrete flashing and the roof floor slabs, and a brick laying body is arranged on the C20 plain concrete flashing; and the waterproof layer comprises a polymer modified asphalt waterproof coiled material, a heat insulating layer, a slope finding layer, a leveling layer and a rigid whole pouring layer which are laid sequentially. According to the water leakage preventing structure for the roof parapet wall and the construction method thereof, the C20 plain concrete flashing with the height being 300 mm is poured on the roof external edge beam, the C20plain concrete flashing a