In the paper the application of a GA evolutionary algorithm to the structural optimisation of free-form architectural shell structures, as large concrete roofs, is shown. The attention is focused on the need of different computational tools and on the problems involved in multidisciplinary design, as the communication and information exchange. The procedure herein described can be applied to more general problems, involving not only the structural performance, but even functional and constructive requirements. The proposed implementation of the algorithm is efficient, robust and particularly capable to avoid local minimum convergence.