PURPOSE: To perform reinforcement by a method wherein, at a ridge tile, a sealant is adhered on the outer surface of a joint between a channel tile at an upper end and a plain tile (a tile piled below a ridge tile), and between pantiles, the sealant is adhered on the outer surface of a joint between an insertion part and a rail part.

CONSTITUTION: At a horizontal ridge 5a, a sealant 3 is adhered at a joint between channel tiles 1 at an upper end and a joint between the channel tile 1 and a plain tile 2 at a lower stage and a joint between upper and lower plain tile 2. Further, between pantiles 4, the sealant 3 is adhered on the outer surface of a joint between an insertion part and a rail part. The gap of a joint therebetween is closed with the sealant 3, and penetration of rain water and blow-in of a gust of wind are prevented from occurring. This constitution prevents the occurrence of leakage of rain through a joint, flying of tiles due to a gust of wind, and a deviation of the tile and effects reinforcement.