A core object model apt to describe architectural objects and their functionality is one of the keystones to an integrated digital design environment for architecture. The object model presented in this thesis is based on a conceptual framework for computer aided architectural design (CAAD) and aims to assist the architect designer right from the early stages in the design process. For its development the object-oriented analysis method MERODE (Model-based Existence-dependency Relationship Object-oriented Development) is used. After a survey on the role of computers in the architectural design process and on particular Product Modelling initiatives, the model is elaborated in two phases: the enterprise-modelling phase and the higher functionality-modelling phase. Actual design cases and test implementations help to establish the conceptual model and illustrate its concepts. The appendices provide a detailed description of both the object model and one of the case studies. The architectis point of view and the specific nature of the architectural design process are the basic considerations, thus leading to a unique model that hopes to make a valuable contribution to the research area of integrated design environments.