Communication is a challenge in multidisciplinary building design teams. The multidisciplinary nature of the team, in which team members contribute knowledge and skills from within the boundaries of their disciplinary domain, combined with the fragmented building design process, makes exchanging information among disciplines difficult. Addressing this challenge is important because communication impacts project outcomes. While effective communication mitigates project risk, contributes to conflict resolution, and reduces project waste and errors, ineffective communication contributes to project failure. Existing research on communication and teamwork provides us with two key insights: first, the presence of different disciplines – the functional diversity – on a team can lead to both positive and negative outcomes through different communication processes; then, communication in design includes three categories – communication as social behavior, as an information process, and the use of communication technology. However, this research comes from domains such as healthcare, manufacturing, and software design. As such, there are several gaps that limit our understanding of multidisciplinary building design communication: a. As literature on multidisciplinary building design teams is sparse, we do not have sufficient documented information about multidisciplinary building design practice to the extent that we use the terms multidisciplinary and interdisciplinary interchangeably although they indicate different kinds of team functioning. b. There are no approaches to studying communication in building design teams that account for the multidisciplinary nature of the team and the complexity of design communication. Identifying an approach to studying communication is a first step to improving team communication and project outcomes. c. Though it is acknowledged that functional boundaries in a multidisciplinary team influence team functioning, the lack of literature on multidisciplinary building design teams and the lack of an approach to studying team communication means that we do not know how functional diversity affects team communication and outcomes. My research contributes to our understanding of multidisciplinary building design team practice by developing a framework to explore multidisciplinary building design communication. Then, it applies the framework to three cases of multidisciplinary building design teams to explore the effects of functional diversity on building design team communication and outcomes. The exploratory framework allows for the systematic description and analysis of multidisciplinary building design teams, their communication, and their outcomes. When applied to the three cases, multidisciplinary building design practice is explored along three lines of inquiry: What constitutes a multidisciplinary building design team? How do multidisciplinary building design teams exchange information? And, what are multidisciplinary building design team outcomes? Data for the case studies are obtained from interviews of 32 industry experts spanning 13 disciplines across the three case studies. This data is analyzed using content analysis and a communication analysis approach that accounts for all three categories of communication. Findings from the case studies do the following: they posit a relationship between functional diversity, communication, and outcomes that is dependent not only on team characteristics, but also on project characteristics and timing; they offer modifications to the exploratory framework that allow for a more accurate representation of building design practice; and provide strategies used by team members to deal with the challenges and complexities of multidisciplinary building design communication. These contributions – the framework and the case study insights – provide building design researchers and practitioners with insights into building design teams, their communication, and their outcomes. They are intended to be a necessary first step towards improving building design team practice.