This study analyzes the effect of the layout and percentage of sails on the seismic performance of buildings, using non-linear static and dynamic analyses. It shows that a wall ratio of 1.0% is optimal for a 7-storey building, and 1.5% for a 14-storey building. Beyond that point, gains are limited and uneconomical. Centered walls offer better performance than peripheral walls, especially when they form complete configurations (U, L, box). Partial walls reduce stiffness and cause local degradation. The study thus confirms the usefulness of non-linear analyses for optimizing seismic design.