PURPOSE: To improve workability by burying a groove forming member to the upper section of the roof rising section of a concrete building and fixing the upper end of a waterproof-layer protective plate to the groove forming member through or without a protective-plate holding member.

CONSTITUTION: The waterproof layer 6 of a roof rising section 5 such as a parapet is covered and protected with a protective plate 4. When the protective plate 4 is installed through a method of fitting previous mounting construction, the upper end of the protective plate 4 is fixed directly to a groove forming member 2 buried to the rising section 5. The lower end of the protective plate 4 is fastened with mortar 9, and a durable floor layer 7 is formed by lightweight concrete, etc. The protective plate 4 is set up between a rail-shaped member 8 fitted onto the floor 7 and the groove forming member 2 at the time of a method of fitting afterward mounting construction, a protective-plate holding member 3 connected to the groove forming member 2 through a fitting section is slid, and the upper end of the protective plate 4 is held by the holding piece while being surely fixed by a rocking preventive body mounted on the holding piece. Accordingly, the execution of works is enabled through the desired methods of construction, and the methods can correspond to different plate thickness easily.