The paper presents an investigation that aims at describing the behaviour of designers, designers' client and products' end user in collaborative design sessions, which are characterized by language barriers and significant differences in the background and competencies of the involved stakeholders. The study has been developed within a European project aimed at developing a Spatial Augmented Reality based platform that enriches and facilitates the communication in co-design. Through the analysis of a real case study in the field of packaging design involving a team of ten design actors, the paper analyses with an original joint approach both the gestures and the verbal interactions of the co-design session. After describing the two tailored coding schemes that capture different facets of, respectively, the gestures and the content of the communication occurring between the participants, the paper describes the partial results and the outcomes of the joint analysis, revealing the importance of combining the two forms of study to suitably characterize the behaviour of the design actors.