Considering integrated CAAD environments for architectural design, a number of different approaches are possible. This paper presents the policy of the CADLAB at the KU Leuven University, where design support right from the first design phases is a basic consideration. After a short introduction on the theoretical framework and additional design tests, we will discuss the core object model that forms the cornerstone for the contemplated design environment. This object model describes all possible data, concepts and operations connected with the architectural design process. For its development, we used the object-oriented analysis method MERODE. The starting-points and main aspects of the model will be discussed, illustrated with examples of implemented prototypes. The architect's point of view and the specific nature of the architectural design process were always kept in mind, thus leading to a model that hopes to make a valuable contribution to the research area of integrated design environments.