Building Information Modeling uses digital tools to build structures before materials are used. Instead of a flat set of 2D drawings, Building Information Modeling digitally builds the structure in 3D and provides a wealth of information on the parts of the structure. Each wall, duct, and piping structure, and even a building’s support, has information attached to it. The information can include dimensions, material, manufacturer data, and information on when the structure needs maintenance.
Most commercial and institutional buildings use some form of Building Information Modeling. The software most companies use to create Building Information Modeling is either Autodesk Revit, Bentley, or Graphisoft. It provides a reference point for the functioning of the building for the designers of the building and the building’s supporting systems. Building Information Modeling connects the design of a building with data about scheduling and costs. This is where Building Information Modeling justifies having the ‘Information’ part of its name.
Building Information Modeling is different from other 3D CAD software due to the information embedded in each object. A door in Building Information Modeling is not a simple rectangle; it is a 36-inch fire-rated door with a specific hardware set. Building Information Modeling is able to track where doors are and how they relate to the walls they are mounted on. This creates a level of intelligence in Building Information Modeling software that encompasses clash detection and helps with the process of taking quantities of building parts and coordinating building systems.
A useful illustration: on a mid-size hospital renovation, a BIM model would contain 40,000+ objects (or more) across 4 or 5 discipline models and would be used for coordinating the design. Finding a clash of a duct versus a beam in that coordinated model during design review would be very inexpensive. Finding that same clash in the field, post duct installation, would mean a costly (and unbid) change order and would likely result in delays of 2 or more days.
LOD (Level of Development) comes into play too, in this scenario. At LOD 200, a model would be representing conceptual massing, while at LOD 400, a model would be ready for fabrication, and contracts address at what LOD a model should be at various stages of the project.
The last part of this half of the BIM equation is Interoperability. Different disciplines often work in different authoring software, and getting a structural engineer’s model to talk cleanly to an architect’s Revit file, or to a mechanical contractor’s fabrication software, depends on open exchange formats and disciplined modeling standards agreed on before design even starts. Skip that agreement, and you end up with models that technically open in the same coordination software but don’t actually align geometrically, which defeats much of the point.
