Abstract. Recognizing the uncertainty of future city development is the basic starting point of sustainable urban planning. Flexibility in design enables the development of “age-friendly cities”, reducing the risks of functional failures caused by changing living circumstances. Planning strategies that enable adaptation of the system to changing environmental, functional, social and technological conditions are essential to the long service life and the resilience of buildings and hence to sustainable city development. This paper considers the implementation of flexible design strategies within the concept of sustainability, defined as a key tool of urban renewal and resilient city development. Value-enhancing flexibility in urban and architectural design is an essential resource for all participants of integrative city development: designers, managers, financial analysts, investors, regulators and academics. Considering this, it is essential to support the flexibility in both conceptual and legislative framework of sustainable urban strategies. Key words: sustainability, flexibility, adaptability, urban resilienc
