This paper deals with a multi-objective design/optimization grid-shell problem. Structural behavior and light absorption/shading have been selected as fitness functions. Such performance criteria can separately lead to different and divergent optimal solutions but, if they are considered as a whole, they are expected to result in several equivalent or similar sub-optimal shapes. This multi-objective optimization problem has been performed here with the aid of a Genetic Algorithm (GA). GAs explore and search widely for suitable solutions and, in this way, they become design tools rather than solution ones. Three benchmarks were established and then a more complex application was made to an existing case study, i.e. the Esplanade in Singapore, designed by DP Architects (DPA) and Michael Wilford & Partners (MWP).