The paper provides extensive case study research involving existing projects distributed across different scales, countries, water types, times, and functions. Identifying and cataloguing available and exemplary existing projects lays the foundations for creating an open-source archive of projects and solutions that allows the development of standard requirements and guidelines for floating building design. A preliminary screening based on specified criteria led to selecting 25 case studies, mainly designed for permanent inhabitation or public use, that are analysed following a requirement-structured rubric. The requirement-structured rubric and case study analysis protocol are evaluated by experts in different disciplinary domains and refined accordingly. The case studies illustrate the different technical and technological advancements in floating architecture, the challenges and opportunities associated with floating buildings and their aggregation in districts, and most importantly, their compliance with each requirement. A multi-criteria evaluation matrix returns best practices among the case studies according to their compliance with the requirement rubric and the priority distribution among requirements according to their fulfilment among the case studies. The multi-criteria matrix proved to be a helpful tool for comparing the different requirements and projects to make informed decisions in a structured and systematic manner.