What Is BIM?

Teams get into trouble when a model looks finished and the parameters are empty or wrong. A door family that is the right width on screen and the wrong size in the schedule will fail a submittal. BIM standards exist so authors fill the fields downstream users will trust: type marks, system names, classification. If nobody named those fields in the BIM execution plan, nobody should be surprised when they are blank.

Authoring tools differ. The coordination problem is the same. An architect’s model, a structural model, and an MEP model meet in a federated view. Clashes found there are only meaningful at the LOD the team agreed. A generic duct at LOD 200 colliding with steel is a warning. It is not a fabrication issue yet.

On most projects the sealed drawings and specifications remain the contract documents. The model is a means of producing and coordinating them. Some contracts do make a model contractual, with explicit LOD and authorized uses. That has to be written. Assuming the contractor can build from a design model because it is 3D shifts risk onto a file the engineer may have modeled only for design.

Content also varies with phase. An SD model can carry massing and a few systems. A CD model should carry the assemblies the sheets show. Neither one contains everything a facility manager will eventually want. Record modeling, when it is in the contract, is a separate scope at closeout.

Industry Foundation Classes is an open format for exchanging model data. It is not the same acronym as issued for construction. Exports lose or rename data if the authoring tool and the receiver map fields differently. A successful IFC handoff is tested on the fields the receiver will use, not on whether the geometry "looks right."

OpenBIM workflows rely on that exchange so an owner is not locked to one vendor’s file. The test is practical: can the coordinator read the system name, the level, and the type, or only the mesh. If only the mesh arrived, you exchanged a 3D drawing.

Virtual design and construction is the broader practice of using models to plan the build: sequencing, coordination, quantities, site logistics. BIM is the modeling process those plans depend on. A VDC manager may not author the architectural model and still run the federated coordination. Job posts mix the titles. The work split is worth reading before you hire or buy software.

Quantities taken from a model are only as good as the elements that were modeled and the rules used to measure them. A missing layer or an unjoined wall changes the takeoff. Estimators who treat model quantities as a starting point, and check them against the drawings, are using the model honestly.