Abstract: A roof plate mounting assembly including a base member fixedly mounted to a well-known tight frame, the base member having upward extensions respectively provided at both lateral ends of the base member and locking jaws respectively inwardly bent from the upward extensions, an inverted U-shaped roof plate support member slidably coupled to the base member, the roof plate support member having wings provided at respective lower ends of the roof plate support member and upward extensions respectively extending from the wings, the upward extensions being loosely engaged in spaces respectively defined by the upward extensions and locking jaws of the base member such that the roof plate is slidable along the upward extension of the base member, a seam protecting cap extending so as to protect overlapping connecting edge portions of roof plates being coupled to each other, the seam protecting cap having downward extensions respectively downwardly extending from both lateral ends of the seam protecting cap and inwar