<p>Circular and adaptable strategies in building reuse are key to achieving a resource-efficient and future-proof built environment. Despite significant advances in circular building research, this field is affected by a significant theory–practice gap. To bridge this gap, we applied an action design research methodology, implementing a circular building design framework over a five-month period in the context of a Dutch monumental office building reuse. The objective of these interventions was to observe practitioners engaging with the framework and identify the barriers they encountered when considering and applying circular building strategies. We observed that the framework primarily functioned as a descriptive tool. Enhancing its usability and effectiveness required several refinements, including simplifying its self-description, clarifying its strategies through practical solutions and connections to related models, providing robust assessment tools, and improving its accessibility. Through iterative action research conducted during the observation and intervention period, we addressed these issues and advanced the framework. Our design-oriented approach led to the development of key design artifacts: a prescriptive guiding, assessment, and reporting tool; a stepwise approach to streamline application; and a hands-on worksheet for practitioners. These artifacts were integrated into a user-friendly platform, transforming the framework into a practical tool for real-world implementation. For theory, this study incorporates a circular perspective into a usable framework and demonstrates how an action design research approach can co-develop and improve frameworks and their usability and relevance. For practice, the produced artifacts represent boundary objects tailored to practitioners’ needs; thereby paving the way for future circular adaptive reuse. Clinical trial number: not applicable.</p>