Circularity aims to reduce waste by closing and narrowing resource loops and by extending the lifetime of materials and products. As a consequence of this fundamentally different approach to construction practices, implementation entails a different organization of the building process. The purpose of this research is to make recommendations with respect to the actor network and the decision-making process to facilitate implementation of circularity in construction practices. First, a theoretical framework is developed to structure and prioritize decision-making to implement circularity based on resource and value strategies. Second, this framework is applied to three circular building cases in the Netherlands, relying on stakeholder interviews and documentation. These cases include a renovation project, a newly built project, and a transformation project. Third, analysis of the case study data demonstrates the actor network and decision-making process including the following aspects: Actors, resources, relations, positions, influence, and decision rounds. It can be concluded that: i) some conventional actors have acquired knowledge on circularity; and ii) expert actors emerged who have specialized in circularity. Both types of actors are a prerequisite iii) to implement circular strategies for the beginning and end phase of the building's lifetime; and iv) should be involved early on (in the design-making processes) to influence decision-making on circularity, especially concerning the long-lived layers of a building.