First question, is LOD the Level of Detail or Level of Development? Accepted terminology is “level of development” (and not only in AIA E202 BIM Protocol Exhibit). Anyway, there is a great difference between development and detail, like between quality and quantity of information. Even if LOD seems to be a sum of measured items (LOD 100 to 500), it is not. It is defined by the purpose of the modeling.
If you just want to use the model for a simple and global analysis of the building, place in space and have some estimative costs, a LOD100 is what you need. And here things stay clear: low detail, low qualifications, short terms, not so reliable results.
Next level, aka LOD200, is easy to achieve, and this because you are still on a conceptual level, using generalized systems. Even quantities, shape and size, location are not important. This result is used also for a general analysis, forecast, and an overview of next stages and coordination requirements. Now, if we quantify the purpose of the BIM model, who needs it and when, we see that LOD 200 may have something also from levels above.
Middle level, LOD 300, seems to be the most practical and reachable. Now you can use this BIM to estimate, visualize, scheduling, but also to construction coordination. That means now you may have 3D models and 2D drawings (for construction, shop drawings). Your systems may be checked for clash detection. Objects start to gain parameters and properties which include them in standards and libraries. General items loose space in this stage. Now you can buy prior to build. Is LOD 300 suitable for a contractor to start fabrication of project components? I think no, so let’s jump to the next level.
LOD 400. Purpose? To help specialty trade contractors and fabricators to build and fabricate project components including MEP systems. That means you can build or install. You have all you need to do it. Architect has nothing to do here, it’s not the moment to change construction plans…
We talk about BIM. That means coordination. The building is constructed, ready to move in. That means the model is now at LOD 500, suitable for maintenance and operations system (this is the meaning of a BIM coordination – to have the model as-build and the building ready at the same time). What happens if the purpose of the project is maintenance? You need the model as-build but LOD 400 information suitable for fabricators or trade contractors it’s just unnecessary. Each time the purpose of modelling guide you to mix LOD levels. It’s the key to fit in costs and time requirements.
Till next time!