The paper is devoted to the description of the methodology and research by design carried out to identify solutions enhancing the functional flexibility of a high-rise building located in Warsaw at. Grzybowska Street. The work presents the theoretical background as well as the conducted research and methodology. The scope of solutions related to functional flexibility concerned the interchangeability of service functions in the podium part of the building, changes in the use of the parking lot, and the provision of the means of changes in the arrangement of types and variants of types of apartments on the apartments levels. The investigation was carried out in the pre-design and design phases. Objectives and criteria of solutions were defined, and research works were carried out through iterations and checking in terms of the cost-effectiveness . The adopted solutions consist in designing the optimal hard portion of the building – the core, the structural system, the arrangement of zones and installation rooms, and the use of structural and spatial over-designed systems. An optimal facade module has been developed. The research aims to introduce the design practice to the issue of flexibility, which is nowadays important for economic and environmental reasons.