To mount a facing member on an external surface of a building without bending the facing member or without marring the appearance of the same by screws etc.

The facing member (vergeboard 2) has projections (linear projections 3) formed on a rear surface thereof, which projections abut on the external surface of the building (side end 1a of a roof panel 1). The facing member is reinforced by the projections, and therefore it is free from a fear of bending. Then a gap 4 is defined by the rear surface of the facing member and the external surface of the building, and a mounting means (hook-and-loop fasteners 5) is arranged in the gap 4, for mounting the facing member on the external surface of the building. Therefore the facing member can be mounted on the external surface of the building by the mounting means, without screwing screws 11 from the outside.