he implementation of circular economy principles in building activities holds the potential for substantial environmental, economic, and social benefits. Although extensive research has examined the impact of circularity strategies on various aspects of buildings, there is a significant gap in the literature focusing specifically on building components and systems (BC&S). Most existing studies developindicators applicable to buildings as a whole or solely at the materials level. This study aims to address this gap by identifying and emphasising specific circularity criteria for BC&S, including structure, infill, and services. The primary objective is to elucidate the contribution of each system to the overall circularity of buildings, thereby prioritising the most impactful circularity aspects. At the component level, it is essential to consider the specific attributes of component assemblies that constitute a system. To enhance the practical application of these findings, the study is supplemented with relevant case studies demonstrating best practices for circularityin BC&S. These case studies provide empirical evidence and practical examples of how targeted circularity strategies can improve the sustainability and efficiency of building practices, thereby advancing the goals of the circular economy