Corrugated sheet metal provided with a flat surface comprised between two lateral edges, and one or more projecting frets, wherein the first lateral edge consists of a box-shaped stiffening profile with a high compressive strength that projects with respect to said flat surface, in parallel position on the same side from which said frets protrude; the second lateral edge consists of a housing profile with suitable shape and dimensions so as to exactly accommodate said stiffening profile of an adjacent identical sheet of corrugated sheet metal; wherein said stiffening profile comprises: - an inclined wing projecting from said flat surface of said sheet metal, and - a flat wall supported at the end of said inclined wing in parallel position to said flat surface of said sheet metal, said housing profile comprises: - a first inclined wing projecting from said flat surface of said sheet metal, and - a flat wall supported at the end of said first inclined wing in a parallel position to said flat surface of said sheet metal and at a height that corresponds exactly to the one occupied by said flat wall of said stiffening profile, characterized in that said stiffening profile comprises a U-shaped profile with substantially square section that extends from the inner side of said flat wall and is provided with a height such that its rear end is flush with said flat surface of said sheet metal; said first inclined wing of the housing profile has a height and inclination equal to those of said inclined wing of said stiffening profile, but facing the opposite side; said housing profile comprises a second inclined wing that projects from the opposite side of said flat wall with a corresponding opposite inclination to that one of said first inclined wing, with respect to which it has a lower height. the first lateral edge consists of a box-shaped stiffening profile with a high compressive strength that projects with respect to said flat surface, in parallel position on the same side from which said frets protrude; the second lateral edge consists of a housing profile with suitable shape and dimensions so as to exactly accommodate said stiffening profile of an adjacent identical sheet of corrugated sheet metal; wherein said stiffening profile comprises: - an inclined wing projecting from said flat surface of said sheet metal, and - a flat wall supported at the end of said inclined wing in parallel position to said flat surface of said sheet metal, - an inclined wing projecting from said flat surface of said sheet metal, and - a flat wall supported at the end of said inclined wing in parallel position to said flat surface of said sheet metal, said housing profile comprises: - a first inclined wing projecting from said flat surface of said sheet metal, and - a flat wall supported at the end of said first inclined wing in a parallel position to said flat surface of said sheet metal and at a height that corresponds exactly to the one occupied by said flat wall of said stiffening profile, - a first inclined wing projecting from said flat surface of said sheet metal, and - a flat wall supported at the end of said first inclined wing in a parallel position to said flat surface of said sheet metal and at a height that corresponds exactly to the one occupied by said flat wall of said stiffening profile, characterized in that said stiffening profile comprises a U-shaped profile with substantially square section that extends from the inner side of said flat wall and is provided with a height such that its rear end is flush with said flat surface of said sheet metal; said first inclined wing of the housing profile has a height and inclination equal to those of said inclined wing of said stiffening profile, but facing the opposite side; said housing profile comprises a second inclined wing that projects from the opposite side of said flat wall with a corresponding opposite inclination to that one of said first inclined wing, with respect to which it has a lower height.