Shared mental models have been shown to enhance team performance. However, research has not observed the different types of sharedness of mental models that may uniquely impact the design process. Therefore, this study examines the types of sharedness of mental models that occur in design teams using Conversation Analysis on data collected from two design teams that performed activities in the early design process in a controlled lab environment. Designers were asked to develop an agreed upon list of ranked design principles, and then generate one or two solutions using the list. These design activities allow for the examination of the varying ways that designers share knowledge, negotiate, and reach understanding. Through our analysis, we identify characteristics of conversation that designers used to build shared understanding. Our results also show how team mental models are built from patterns of conversation that are evident during open-ended and unstructured design discussions. This work sets a foundation for future research to gain a deeper understanding of how designer mental models are shared in unstructured conversations that take place during design practice.