This Guide to Coalition Building outlines the parameters of coalitions in the circular building economy. National cases vary on actors involved, but the key is information as an essential element towards policy requirements. The transition to the circular building economy does not occur by decree. The process involves many actors, from small and large firms to the public sector and end-users. Not only are there actors involved, but there is also a need for innovations and institutional changes, from work processes and digital infrastructures to updating of regulations and building codes. Furthermore, at the EU level there are developments that ultimately aim to make the circular economy compatible with the single market. This very broad constellation of actors, processes and institutions is the environment in which the circular building economy takes form. For the practical task of starting circular building projects there is a great need for (temporary) coalitions, that operate in this environment towards a specific goal, such as a building permit for a construction using reused materials. In this guide for coalition building, I argue that to achieve the goal, there has to be an alignment between the actors in the circular value chain on the one hand, and the permit-issuing authorities on the other hand. The policies on basis of which building permits or zoning plans are issued, are determining what is the exact information needed from the circular value chain. However, these policies also vary by country and even by location, as local authorities may have specific climate change mitigation policies. To a substantial degree, the national building codes are nonetheless shaped by EU level recommendations and directives. Therefore, transitioning to a circular building project involves a lot of knowledge of (locally valid) rules, institutions and strategies. It also requires managing a coalition in which actors may have different incentives and must be willing to share information/data and think through the whole circular value chain in terms of information required (see Wijewickrama et al. 2021). Interaction between these so-called construction project coalitions and regulation coalitions may also involve external actors, such as firms that perform accreditation of the building materials or provide a certified calculation of Life Cycle Assessment (LCA). Concludingly, the transition to a circular building economy is not only dependent on technical innovations and their implications, but also on information flows between actors in the circular value chain. Furthermore, the transition depends on a smooth flow of information between the two coalitions. Interpretation, demand and supply of information are vital to manage the implementation and scaling of circular economy solutions.