Level of Development (LOD) describes how far a model element has been developed, and so how much the people using the model can rely on it. It is set per element and per stage, not for a whole model. The scale is widely used in North America and on international projects, and is defined in the BIMForum Level of Development Specification.
At a glance
| Defined by | BIMForum LOD Specification (updated regularly); origins in AIA documents from 2008 |
| Values | 100, 200, 300, 350, 400, plus 500 for field verification |
| Applies to | Each element category, at each milestone |
| Recorded in | An LOD matrix, usually an appendix to the BEP |
| Related | Level of information need (ISO 7817-1), which replaces it in ISO 19650 contexts |
The levels
| LOD | Meaning in plain words | Reliable for |
|---|---|---|
| 100 | A symbol or generic mass shows something is there | Area, volume and early cost studies |
| 200 | A generic element with approximate size, shape and location | Design development and early coordination |
| 300 | A specific element with designed size, shape, location and orientation | Coordination, drawings, quantities |
| 350 | As 300, plus the interfaces with other systems (supports, connections, clearances) | Detailed coordination between trades |
| 400 | Detailed enough to fabricate and install | Fabrication, shop drawings, installation |
| 500 | Verified in the field as installed | Record and handover (a statement of verification, not a further development step) |
Each level also implies non-graphic information: at 300 a door has its dimensions and fire rating; at 400 its specific product.
Development is not detail
LOD is about reliability, not visual richness. A beautifully detailed manufacturer's object placed in roughly the right spot is still LOD 200 if its position and size are not designed. A plain box can be LOD 300 if its size and position are fixed and coordinated.
How it is used
Teams agree an LOD matrix: element categories down one side, milestones across the top, a target LOD and a responsible party in each cell. The matrix tells coordinators what can be clash-tested at each stage, tells estimators what can be measured, and tells contractors what they are taking over.
Common mistakes
- One LOD for the whole model ("the model is LOD 300").
- Confusing LOD with level of detail (sometimes also written LOD).
- Asking for 400 at design stage for elements the designers do not specify.
- No responsible party per cell, so nobody develops the element.
- Assuming 500 means "more detail than 400". It means checked against what was built.
Where to read more
BIMForum publishes the LOD Specification with element-by-element descriptions and illustrations. For ISO 19650 projects, see LOD vs LOIN.