Elements usable in the construction of a building or a roof having the shape of a curved surface, characterized in that said elements are panels (1a, 2a, 3a, 4a, ...) of light material of which the shape corresponds to that which is obtained by cutting, on said surface, elements (1a, 2a, 3a, 4a, 5) delimited by a curved polygon having from three to six sides, and method characterized in that a former is made which is comprised of at least two juxtaposed shells having each a shape corresponding to that of said curved surface, each shell consisting of an assembly of said prefabricated elements, the inner face of the outer shell coinciding with the outer face of the contiguous inner shell.