To promote consistency across the AEC industry for defining and communicating levels of detail (LOD) on a BIM project, BIMForum, with participation by AIA, AGC of America, PCI, BIM-M, MBMA, CD-BIM.com, and NISD, annually publishes the LOD Specification guide.
The guide defines and illustrates features of model elements of various building systems at different phases of a project as it comes together. This allows downstream users to clearly understand the usability, content and reliability of models they receive from model authors and also defines scopes of work to eliminate overlap or duplication. In its April, 2019 LOD commentary, BIMForum explained that the goal is for the LOD Specification to become a useful communication tool. It was not intended to prescribe what levels of development coincide with certain points in a project, as that description is up to the author(s) of the BIM model. The 2019 LOD Specification is available for download from BIMForum.
In its January, 2019 blog article “BIM Detailing,” MLP Consulting described six levels of detail used in the AEC industry. As the article points out, “It is crucial to define this LOD at the beginning of the project, and at which points in the project life-cycle the LOD will increase. The numbered levels don’t necessarily need to correlate to a specific project stage. What’s important is that the required level of detail is clearly understood by all stakeholders at each stage.” Except for level 100, where only graphic information is included, in all other levels non-graphic information and data (ie. codes, schedules, manufacturers, model numbers) may or may not be attached.
The following graphic by SRINSOFT, from the online article “BIM Level of Development,” is one example of the way LODs are used by project stakeholders.
