1. What is Level of Development (LOD)?
Level of Development (LOD) is a standard defined by the American Institute of Architects (AIA G202) and BIMForum that specifies the degree to which an element's geometry and attached non-geometric information can be relied upon by project team members.
LOD governs reliability rather than just visual detail. It prevents engineers and contractors from relying on generic early-stage geometry for detailed fabrication decisions.
2. Breakdown of LOD 100 through LOD 500
| LOD Level | Geometric Representation | Reliability & Use Case |
|---|---|---|
| LOD 100 | Conceptual massing or symbol; no specific size or shape | Feasibility study, spatial planning, cost per m2 estimation |
| LOD 200 | Generic geometry with approximate size, shape, location | Schematic design, structural framing layout, preliminary sizing |
| LOD 300 | Specific geometry, accurate dimensions, location & orientation | Detailed design, planning submission, quantity takeoff |
| LOD 350 | Model element plus connection interfaces & support geometry | Multi-disciplinary clash detection (e.g., rebar clearance, plate stiffeners) |
| LOD 400 | Fabrication-level detail (shop drawings, rebar schedules, bolts) | Direct manufacture, off-site steel fabrication, rebar bending schedules |
| LOD 500 | Verified field as-built condition (geometry & COBie asset data) | Facility management, operations & asset maintenance |
3. LOD Applications in Structural Engineering
In structural steelwork design, moving from LOD 300 to LOD 350/400 transitions the model from member centerline sizing to modeling actual end-plate connections, gusset plates, weld symbols, and bolt assemblies.
For reinforced concrete, LOD 300 represents solid concrete geometry; LOD 350 includes main reinforcement bars; while LOD 400 incorporates couplers, stirrup lap lengths, and rebar bending schedules (BS 8666 compliant shape codes).
Implementing LOD Matrix in Projects
- 1
Define Model Responsibility Matrix (MRM)
Assign specific LOD targets per discipline at each project milestone (Concept, Detailed, Construction).
- 2
Avoid Over-Modeling
Do not model LOD 400 rebar during tender stage; match LOD level strictly to project delivery phases.
- 3
Attach COBie Parameters
Ensure LOD 500 asset tags (serial numbers, installation dates, warranty info) are populated prior to handover.