Design tasks, in particular architectural design tasks, have been found hard to support by means of computers. The main reason for this is that design is a problem solving process, which requires a dynamic way of handling information involved in the design process. The research presented in this paper focuses on this aspect of CAAD: the support of design tasks with dynamic, flexible information modelling techniques. The basic concepts for the developed approach is taken from the field of Feature-based modelling. We briefly review these concepts and then interpret and transport them to the context of architectural design. In defining types of Features, a distinction is made between domain-specific Features and generic Features for which we propose a classification. A framework for the definition and modelling of Features is discussed as well as a prototype Feature-based Modelling Shell based on this framework.