A method for securing a roof sheathing and shingles in a retrofitting reinforcement of an existing roof structure, the shingles being laid on the roof sheathing in a partially overlapping pattern, comprises (a) driving a plurality of fasteners down through selected shingles and the roof sheathing in a selected area of the roof structure into at least one of underlying roof frames; and (b) applying a water-resistant coating to the roof structure to seamlessly cover exposed surfaces with exposed ends and sides of all shingles in the selected area.