In our previous article, LOD Secrets You Did Not Know, we explored the concept of Level of Development (LOD) in detail. Today, we revisit this topic to provide a clearer understanding of LOD, especially within the context of BIM. Our aim is to define the content and detail levels of BIM models to facilitate efficient project delivery and foster collaboration across disciplines and throughout the project lifecycle.
Since 2011, the BIMForum working group, under the American Council for Integrated Construction (AGC), has collaborated with the American Institute of Architects (AIA) to develop comprehensive LOD specifications. Through bi-weekly meetings and building upon the LOD definitions in AIA E202, they have progressively refined the LOD requirements for each building system, supported by practical case studies. This standard was officially finalized and published online in 2013, with plans for annual reviews and updates.
This updated LOD specification plays a vital role in the BIM Project Collaboration Framework, currently being developed jointly by AIA, AGC BIMForum, and the buildingSMART alliance. Beyond clarifying LOD definitions for individual building system components, several key points have been summarized as follows:
1. Distinguishing Level of Detail from Level of Development: Level of Detail refers to the amount of information or the intricacy included in the model components — essentially, the input data. In contrast, Level of Development refers to the reliability and accuracy of both geometric and attribute data within model components, which determines how the model can be used.
2. Introduction of LOD350: To support cross-disciplinary collaboration, an additional level, LOD350, has been introduced alongside the original five levels (LOD100–LOD500). LOD350 represents LOD300 enhanced with detailed interface information required for assembling building systems or components.
3. Scope of LOD Definitions: Currently, detailed definitions are provided for LOD100 through LOD400. The definition of LOD500 remains consistent with the original AIA specifications, as the BIMForum working group sees no need for further refinement at this stage.
4. Important Conceptual Clarifications: First, there is no strict correlation between levels of development and specific stages of the engineering lifecycle, since different building systems progress at varying rates during design. Second, the notion that a model exists at a single LOD is inaccurate; BIM models at any stage will contain components at various levels of development. Not all components need to be, or can be, developed to the same LOD simultaneously.
That concludes our additional insights on LOD today. We hope this information proves valuable for those looking to deepen their understanding of Level of Development within BIM.
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