Level of Development vs level of detail
'Level of detail' describes how much geometry an element has. 'Level of Development' – the meaning used in the BIMForum LOD Specification – describes how much you can rely on it: is its size, location and type decided, or still a placeholder? A beautifully detailed chair family can be LOD 200 if nobody has chosen the actual product yet.
That is why LOD is assigned per element, not per model. In the same model, walls may be LOD 300 while furniture is LOD 200 and MEP is LOD 350. A Model Element Table in the BIM Execution Plan records which LOD each element needs at each stage.
The LOD levels one by one
| LOD | Meaning | Example: a wall | Used for |
|---|---|---|---|
| 100 | Conceptual, symbol or mass | Building mass with floor areas | Feasibility, early cost per area |
| 200 | Generic element, approximate size and location | Generic 200 mm wall | Schematic design, option studies |
| 300 | Specific element, accurate size, shape, location | Wall type with real layers and thickness | Construction documents, quantities |
| 350 | LOD 300 plus interfaces with other systems | Wall with openings for ducts and supports | Multi-trade coordination, clash detection |
| 400 | Fabrication and assembly detail | Framing studs, connections, fixings | Shop drawings, prefabrication |
| 500 | Field-verified as-built | Wall as actually built, verified on site | Handover, facility management |
Note: BIMForum does not define LOD 500 in its specification; it is commonly used in contracts to mean field-verified as-built models.
Which LOD does your project need?
- Design options and client presentations: LOD 200 is usually enough.
- Permit and construction documents from Revit: LOD 300 for the main building elements – see architectural BIM services.
- Clash detection and coordination: LOD 350 for structure and MEP – see BIM coordination.
- Steel or precast fabrication: LOD 400 – see Tekla detailing.
- Existing buildings from scans: LOD 200–300 plus a level of accuracy – see point cloud to BIM.
LOD in the UK: Level of Information Need
Under BS EN ISO 19650, UK projects describe the same idea as the Level of Information Need: for each information requirement, the geometry, alphanumeric information and documentation needed at each stage (defined in BS EN 17412-1). In practice, many UK teams still use LOD language informally, but contracts and EIRs refer to the Level of Information Need.
Common LOD mistakes
- Asking for 'LOD 400 everything' – expensive and unnecessary for most elements.
- Not defining LOD per element and per stage, so modelers guess.
- Confusing LOD with how a model looks in renders.
- Forgetting data: LOD covers information as well as geometry.
Need help writing an LOD matrix for your project? Our BIM modeling team can propose one with the quote.
When you order a model, state both the LOD per element and the purpose of the model in one sentence – for example 'coordination model for MEP clash detection, LOD 350 for structure and MEP, LOD 300 elsewhere'. That single sentence prevents most disagreements about what the modeler should deliver.
LOD for existing buildings
For scan-to-BIM work, LOD alone is not enough, because the question is also how closely the model matches reality. That is why existing-condition models are specified with both an LOD and a level of accuracy (LOA), for example LOD 300 at LOA 30.
How LOD is written into a BIM Execution Plan
The practical tool is the Model Element Table (also called an LOD matrix). Rows list building elements – usually by a classification such as Uniformat or Uniclass – and columns list project stages. Each cell gives the LOD required and the party responsible for modeling it. For example, structural columns might be LOD 200 at schematic design, LOD 300 at construction documents and LOD 400 when the steel detailer takes over.
| Element | Schematic design | Construction documents | Coordination | Fabrication |
|---|---|---|---|---|
| Exterior walls | 200 | 300 | 350 | – |
| Structural steel | 200 | 300 | 350 | 400 |
| Ductwork | 100 | 300 | 350 | 400 (if prefabricated) |
| Furniture | 100 | 200 | 200 | – |
LOD and information, not just geometry
A frequent misunderstanding is that a higher LOD simply means more 3D detail. The BIMForum specification also describes the information an element must carry. An LOD 300 door has its real size and location, but its type data – fire rating, hardware set, acoustic rating – is just as important for schedules and specifications. When writing requirements, list the parameters you need as well as the LOD.
How LOD affects cost and schedule
Each step up in LOD adds modeling time, especially for MEP and structure. Modeling every pipe hanger at LOD 400 can multiply the effort compared with LOD 300 pipework. Specify high LODs only where someone will use them – for coordination, fabrication or facility management – and keep the rest lower. Your modeler should be able to tell you how the LOD matrix affects their price.
Checking that a model meets its LOD
Ask for a short model audit at each milestone: a sample of elements per category checked against the matrix, a list of placeholders still at a lower LOD, and the model health report. Tools such as Solibri, Revit schedules or simple Dynamo scripts make this quick.
