BIM model depth is categorized into three distinct levels. This classification ensures that all stakeholders in construction projects share a common language and consistent standards when describing the content and level of detail required in BIM models. These levels primarily help define the project’s deliverables, clarify user needs, and specify detailed client requirements in contracts.
It is important to note that the model depth level does not directly correspond to the design phase. Instead, the required depth level should be tailored to the specific needs of the project. For instance, when modeling interior wall finishes, a Level I depth during the construction drawing phase may be adequate to fulfill design requirements. Assigning a Level III depth mechanically, based solely on the depth level definitions, may not be appropriate.
For projects with particular demands—such as complex foundations, challenging geological conditions, or extended construction timelines—the structural foundation design might need to meet construction drawing depth requirements already during the preliminary design phase. In such cases, specifying Level III depth for the basic structural engineering design is necessary, rather than limiting it to Level II based on standard depth definitions.
We recommend a key principle for determining the appropriate modeling depth: aim for moderate modeling that sufficiently supports design expression. Both under-modeling (selecting a depth level too low) and over-modeling (selecting a depth level too high) should be avoided.
As an example, in a large-scale domestic project, model delivery at the preliminary design stage typically requires Level II depth. However, core structural elements may need to reach Level III depth, while fire safety components might only require Level I.
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