To improve durability against the stepping pressure of a builder at the time of the execution of works, the temporary placing load of an execution member or snow load applied to a new roof board, and to prevent the damage to an existing roof board.
New roof boards 5 are installed onto an existing roof board 1 through roof-receiving frames 4. The roof-receiving frame 4 has a horizontal board section 7, a pair of fixing leg sections 8 continuously connected at the left-right ends of the horizontal board section 7 and new roof-board fixing sections 9 continuously connected to the fixing leg sections 8. A pair of the fixing leg dections 8 are placed on the bottom sections of the existing roof board 1 and fastened onto a roof foundation material 2 by fasteners 11, and the new roof board 5 is received and borne by the horizontal board section 7. The new roof-board fixing sections 9 of the adjacent roof-receiving frames 4 are superposed and united mutually through hangers 12 between the fixing sections 9, and seam pieces 5c at the ends of the adjacent new roof boards 5 are seamed at the upper end sections of the hangers 12 mutually.