BIM LOD Deconstructed

No, this is not a typo, we’re not talking about lights but about LOD. Can you guess what it is and its role within BIM?

LOD stands for Level of Details or Level of Development as they refer to the same professional standards of the AEC sector will use through the various stages of building, with a slight difference. The level of details is about how a model looks: what is the input of the model. The level of development is the depth applied to the model, the “reliability.” As a component is more developed, more details are provided on it. There are different universal levels of LOD as described below:

Levels of Details

  • LOD 100 – Concept Design
    • Information connected to models (elements & symbols). This information will tell you the present components without their geometric representation (shape, size, location). Hence, it is important to interpret this level of information as an estimate.

Source: BIM Forum
  • LOD 200 – Schematic Design
    • This model’s information is still estimated, but you can access the element’s details such as shape, size, location and orientation. You may also find notes in the model.

Source: BIM Forum
  • LOD 300 – Detailed Design
    • This model is represented through its specific elements. You won’t need notes to refer to here as model information is representative of the project origin. (E.g. Your doorframe is designed in the model as it should be done on-site.)
  • LOD 350 – Construction Documentation
    • Similar to 300, but this model will contain parts necessary for the elements’ coordination, e.g. supports and connectors such as anchor bolts.
  • LOD 400 – Fabrication & Assembly
    • Model is documented in sufficient detail and accuracy for fabrication, assembly and installation of the said element. All necessary information such as quantity, size, shape, location and orientation can be measured directly from the model.
  • LOD 500 – As-built
    • This LOD refers to on-site surveying of the model construction (field verification). It does not define or illustrate the model.

LOD 350 for Construction Layout

The higher the LOD, the easier it is to detect clashes in your BIM model and improve the coordination process. For example, at LOD 300, models are used to create the construction documents needed for the building process. However, these models lacked the detail required for full coordination of the process. At 400, the necessary information may not be obtained until the shop drawings phase. Thus, a midpoint level, LOD 350, was created to bridge this information gap and allow general contractors to perform pre-construction coordination.

LOD 350 models include more element details, disclosing how building components interface with varying building systems and other elements with clear definitions and graphics. For construction layout, a LOD 350 model based is most advantageous. Elements such as hangers are accurately placed with layout points, and footing sleeves or anchor bolts are modelled accurately, ready for field positioning. The model will inform you of the specific areas where adjacent components may interfere with each other. Furthermore, for a LOD 350 model, you can have different levels of BIM, which is what you’ll include as information in your model. For the bidding, you could start with a low level of critical information and then add all the necessary details to your model before a project starts:

  • Low level – Critical Stud Framing (in-post door jam post)
  • Medium level – Interior typical stud framing (Infield between studs)
  • High level – Wall backing (important for hospitals, showing blockings and where they should be installed)
  • Very high (LOD 350-400) – Soffit framing (clash detection with framing)
    • Exterior load-bearing
    • Panelized systems

 

LOD On-site Benefits

When using 3D BIM models conforming to industry standards of LOD, you can expect to experience these results:

  • Positive impact on QA/QC (Revit does clash detection within the varying trade’s components involved)
  • A better decision about delivery and coordination
  • Better bids and estimation (the information is more accurate as it relies on representative 3D models)

The more details you’ll add in your design, the more accurate you’ll be. However, costs are also rising with the level of details. So, keep in mind that modelling at higher LOD increases cost-time and money for the design phase. Gain the most out of your construction design by choosing which LOD is most advantageous for the project at hand.

Conclusion

So LOD defines through the different construction stages the level of detail and reliability of a model. We’ve previously explained on this blog accuracy and its importance in construction, pre-building and on-field. Well, LOD levels play a part in your building accuracy. The more details about your model elements you can visualize pre-construction, the more you can validate an accurate and mistake-free construction plan. Thus, through coordination and clash detection, among other benefits, a construction process will run smoother by working with BIM models of the level of details greater than 300.