The building type is a (knowledge) structure that is both recognised as a constitutive cognitive element of human thought and as a constitutive computational element in CAAD systems. Questions that seem unresolved up to now about computational approaches to building types are the relationship between the various instances that are generally recognised as belonging to a particular building type, the way a type can deal with varying briefs (or with mixed functional use), and how a type can accommodate different sites. Approaches that aim to model building types as data structures of interrelated variables (so-called ‘prototypes’) face problems clarifying these questions. It is proposed in this research not to focus on a definition of ‘type,’ but rather to investigate the role of knowledge connected to building types in the design process. The basic proposition is that the graphic representations used to represent the state of the design object throughout the design process can be used as a medium to encode knowledge of the building type. This proposition claims that graphic representations consistently encode the things they represent, that it is possible to derive the knowledge content of graphic representations, and that there is enough diversity within graphic representations to support a design process of a building belonging to a type.