LOD Defines How Fully Developed a BIM Element Is
Level of Development (LOD) is a standardized way to describe how complete and reliable the information contained in a BIM element is. Without LOD standards, saying a model element exists means nothing - a wall might be a simple mass placeholder or a fully detailed assembly with stud sizes, insulation R-values, fire ratings, and cost data. LOD defines five levels (100–500) that correspond roughly to project phases, from early conceptual design through post-construction as-built documentation. LOD is defined by the BIM Forum LOD Specification and AIA E203. The ARE PDD tests LOD because understanding what level of model detail is appropriate at each phase affects project scope, contract terms, and coordination expectations.
LOD 100: Conceptual
Elements are represented as massing objects - simple volumes without detailed geometry, materials, or accuracy of size. LOD 100 is appropriate for early schematic design or feasibility studies. An LOD 100 wall might be a block showing approximate volume; its actual width, materials, and layers are not yet defined. Quantities and cost estimates from LOD 100 are order-of-magnitude only.
LOD 200: Approximate Geometry
Elements have approximate size, shape, location, and orientation but may not be fully accurate. Generic placeholders are used when specific products are not yet selected. An LOD 200 wall has approximate thickness and height but may not reflect final assembly layers. This level is common at the end of schematic design. Non-graphic information (product data, specifications) is not necessarily attached.
LOD 300: Specific Geometry
Elements have specific size, shape, location, and orientation accurate enough to support conventional coordination and documentation. Dimensions can be taken from the model accurately. LOD 300 is the standard for construction documents. An LOD 300 wall includes all assembly layers, accurate thicknesses, and structural components. Shop drawings typically should NOT be generated from LOD 300 elements without verification - the next level is required for fabrication.
LOD 350: Construction Coordination
Elements have the same characteristics as LOD 300 plus representation of how elements interface with other systems. LOD 350 adds connection details, embeds, and coordination geometry needed to detect clashes and produce coordination models. This is the practical level for multi-firm BIM coordination and clash detection on complex projects.
LOD 400: Fabrication
Elements have the detail and accuracy required for direct fabrication. An LOD 400 steel connection includes exact bolt patterns, weld sizes, and plate thicknesses. LOD 400 is the domain of specialty contractors and fabricators, not typically produced by the design team. Shop drawings are essentially LOD 400 documentation for their respective elements.
LOD 500: As-Built
Elements represent the actual installed conditions, verified in the field after construction. LOD 500 models reflect the actual as-built state and are useful for facilities management, future renovations, and building operations. Achieving true LOD 500 requires field verification after construction, not just contractor red-line drawings.
Key Exam Points
- LOD 100: massing only, early concept. LOD 200: approximate geometry, schematic design.
- LOD 300: specific geometry, construction documents - standard level for CD phase.
- LOD 350: adds interface and connection information for coordination.
- LOD 400: fabrication-level detail, typically produced by fabricators/contractors.
- LOD 500: as-built conditions, verified in field post-construction.
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