A building's strategic asset management (SAM) capability has traditionally been limited by its site-based management. With the emergence of needs from clients about delivering a long-term portfolio-based building asset management plan that minimizes the asset risk and optimizes the value of their asset portfolios, SAM Units have emerged as a new business form to provide various SAM services to their clients. However, the quality of their current data model is still hindered by many issues, such as missing important attributes and the lack of customized information flow guidance. In addition, there is a gap in integrating their existing data collection with various data sources and Building Information Modeling (BIM) to enhance their data quality. By evaluating a SAM Unit's portfolio case study, this paper identifies the factors limiting the quality of SAM Units' data model and develops a guide to integrating various data sources better. We develop a BIM-integrated portfolio-based SAM information flow framework and a detailed hierarchical portfolio-based non-geometric data structure. The proposed framework and data structure will help SAM professionals, building asset owners, and other facilities management professionals embrace the benefits of managing the portfolio-based SAM data.