A method to minimize the cost of the structural design of reinforced concrete structures using Biogeography-Based Optimization, an evolutionary algorithm, is presented. SAP2000 is used as computational engine, taking into account modelling aspects such as static soil-structure interaction (SSSI). The optimization problem is formulated to properly reflect an actual design problem, limiting e.g. the size of reinforcement bars to commercially available sections. Strategies to reduce the computational cost of the optimization procedure are proposed and an extensive parameter tuning was performed. The resulting tuned optimization algorithm allows to reduce the direct cost of the construction of a particular structure project with 21% compared to a design based on traditional criteria. We also evaluate the effect on the cost of the superstructure when SSSI is takeninto account.