According to the American Institute of Architects (AIA) E202 document, the term Level of Development (LOD) describes the expected level of completeness of model components within BIM models at various stages throughout the construction lifecycle. The document defines five LOD stages, ranging from 100 to 500, which have become widely recognized as the standard for explaining the content and detail of building information models.
However, the E202 document only conceptually explains how the expected completeness of model components should align with different application requirements at each stage of development. It does not provide a clear or detailed definition of LOD for individual model components.
In practice, the term LOD is often oversimplified and misused to describe the overall development level of an entire BIM model. It is frequently confused with Level of Detail, leading many to mistakenly believe that all components within a BIM model must become increasingly complete and detailed as the project progresses. This misunderstanding can result in unnecessary complexity, excessive resource consumption during model creation, and disputes related to model delivery.
To clarify the content and detail requirements of BIM models and to support cross-disciplinary and lifecycle collaboration, the BIM Forum working group of the American General Contractors (AGC) partnered with the AIA to develop the LOD Specification. Building upon the LOD framework from AIA E202, this specification gradually provides more detailed definitions of LOD for each building system.
It is important to distinguish between Level of Detail and Level of Development. Level of Detail refers to the amount of visual or geometric detail included in a model component—essentially, the input information that defines it. Level of Development, on the other hand, indicates the reliability and completeness of both geometric and attribute data, which directly affects the model’s usability and applicability.
To address the needs of cross-domain collaborative workflows, an additional development level, LOD 350, was introduced alongside the original five levels (LOD 100 to LOD 500). LOD 350 essentially represents LOD 300 enhanced with interface details necessary for coordination and assembly between building systems or components.
This background explains the origin and rationale behind the detailed division of BIM model development levels. I hope this article provides useful insights for everyone involved in BIM modeling!
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