When discussing LOD, most people immediately think of BIM. The refinement level of a BIM model is represented by LOD, which ranges from 100 to 500. But does LOD only indicate the level of detail? Today, we will reveal some lesser-known facts about LOD.
In reality, the term LOD in BIM originates from the American Institute of Architects (AIA) document E202, where LOD stands for Level of Development. It refers to the expected completeness and integrity of model elements—defined as parts, systems, or components within a BIM model—at various stages of the construction lifecycle.
To put it in terms of traditional engineering drawings, LOD can be roughly mapped as follows: LOD 100 corresponds to Conceptual Design; LOD 200 to Preliminary Design; LOD 300 to Detailed Design; LOD 400 to Construction; and LOD 500 to Completion (As-Built). Intuitively, this means that model components become progressively more complete and detailed as the project advances. This explains why interpreting LOD as Level of Detail is common and seems intuitive.
However, why does AIA’s E202 document use Level of Development instead? This choice is deliberate. The key difference lies in the concepts of integrity versus detail level. Document E202 focuses on BIM model components—rather than the entire model—and emphasizes their integrity. This means that at each stage of the construction lifecycle, BIM model components are expected to have a defined completeness in both geometric and non-geometric information. The completeness is based on the project’s characteristics and the information needed or available at that stage.
Moreover, components within the same project phase may not require the same degree of information completeness. The term detail level is generally used to describe how detailed a model component is, without clarifying whether the information is complete or necessary. It also implies that all components at the same stage should have the same level of detail, which is not accurate. Therefore, the use of Level of Development in E202 avoids the misconceptions often associated with Level of Detail.
That covers the hidden truths about LOD you might not have known. Additionally, it’s important to note that nowadays, people often use LOD to describe the development level of the entire BIM model at a certain project stage. This is a simplified and potentially misleading usage. According to document E202, LOD is intended to define the completeness of individual BIM model components—not the entire model—at different project phases. This helps clarify the responsibilities of the component authors (Model Element Authors).
The definition of BIM model components can refer to standards such as the CSI Uniformat coding system. For LOD to function effectively, it must adhere to its original intent and be applied rigorously. Otherwise, misuse may lead to misunderstandings and disputes.
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