Over the last two years, there has been an increased interest across the Architectural /Engineering/ Construction (A/E/C) professionals in the potential adoption of the Building Information Modeling.  Professional Associations such as the American Institute of Architects (AIA), the Associated General Contractors (AGC) and the Design-Build Institute of America (DBIA) are dedicating specific resources to develop a better understanding on the implications of the use of this concept in their professional activities. However, not much ground has been gained yet in finding effective ways to decide and choose the level of granularity (detail) needed to be maintained while developing the digital model.

Some construction firms are taking an active role investing resources in learning the technology and in exploring areas where highest payoff potential exists. The 3D capabilities of BIM clearly demonstrate its benefits in visualization, constructability analysis, visual scheduling, logistics planning, interdisciplinary systems coordination and clash detection. In addition BIM offers a wealth of information that is created internally as the model develops. These data stored in the model can then be used to generate XD studies, that is, 3D plus time, cost, and other dimensions that complement the communication of information related to the development of the project. 

As a result of these initiatives, many important factors related to the implementation of this concept have been identified. These include:  type of and amount of resources needed, modeling expertise, periodicity of updates, software capabilities, contractual requirements, project organization structure, project uniqueness & complexity, owner buy-in, uses of model output , interoperability with other software, (liability associated to the use of the model, subcontractor sophistication and project phase.  These are all important factors a contractor must carefully weigh against the potential benefits derived from creating and using BIM (AGC, 2006). 

The Level of Granularity (LOG) of the digital model, or level of detail development is a key factor that results from careful consideration of all the above factors. It is a very complex and iterative process. It requires a critical assessment of the value added of adding more details to the digital model versus the purpose of its development whether to enhance the communication process or to support the construction management functions performed by the firm. 

This paper, presents two case studies in which the authors have been directly involved in making the decision on the LOG of the digital model. The first case involves the Togar Suites, Union Station project in New Jersey while the second case refers to the Worcester Trail Courthouse in Worcester Massachusetts. In both cases, the 3D models were developed primarily for visualization of the construction sequence. However, in the case of the Togar Suites the contractor also needed the model for trade coordination and clash detection purposes. 
