This paper discusses the potentialities and critical aspects resulting from the integration of BIM systems in the processes dealing with the Built Heritage (BH). It focuses on the conceptual extension of virtual model triggered by BIM approach and its possibilities of stratifying knowledge. The potential of BH-oriented BIM systems (the so-called Heritage-BIM or H-BIM) is undeniable. However, there remain operational and theoretical issues related to the unsolved aporia between the rigidity of modelling tools and the high flexibility needed when BH elements are involved. The outcomes of our research, tested on case studies belonging to Sapienza Main Campus, led to a clearer understanding of the inner features of the H-BIM model, its structuring in Level of Evolution Models and the adoption of an additional parameter, the Level of Reliability for digital objects.