Building Information Modeling (BIM) is a highly intelligent 3D model-based process that allows AEC (Architecture, Engineering, and Construction) professionals to collaborate in the planning, design, and construction of a building project. When BIM is used on construction projects, the level of detail can range from a broad engineering representation to an accurate as-built model of the building.
A BIM model consists of smart BIM objects that have dimensions and data storage. BIM software updates the model if any element has changed. The Level of Development (LOD) framework is used to determine the status of a BIM item, helping AEC professionals, MEP engineers, contractors, and project managers coordinate and communicate. In some cases, the term “level of detail” is also used, which can be quite misleading. For example, it is still considered a model with a high level of visual detail but no raw technical specifications. Thus, Level of Development (LOD) is preferred as it refers to both visible and non-visual information.
Now that we know what BIM is, let’s take a look at the different level of development involved in BIM.
6 levels of development in BIM
The American Institute of Architects (AIA) has identified 6 levels of development, and each level represents a different design stage in the construction process. As mentioned above, LOD refers to the specific build systems and component and not the complete project. The LOD helps indicate which areas of the design have reached the construction documentation stage.
The definition of “completed form” varies depending on who sees it and for what purposes. For example, the construction documents (LOD 350) are considered as “completed” by the contractors, and on the other hand, the construction form (LOD 500) is considered by the clients as a completed building. As the LOD level rises, so does the level of detail and data contained in the BIM elements.
Let’s dive into the features of the build components in the individual lod stage:
1 LOD 100: Pre-Design
The LOD 100 item does not contain any features such as dimensions, shapes, and exact spot locations. In other words, these elements are represented by generic placeholders that lack physical information. General information about the LOD 100 elements may be available from other components, however, it is considered approximate at this point.
2 LOD 200: Schematic Design
LOD 200 items have approximate features such as dimensions, shapes, locations, etc. and are a bit more complex than LOD 100 items. Non-geometric information may also relate to some LOD 200 items. While most LOD 200 items have general shapes that represent the volume occupied, some These items have recognizable shapes as well. At this point, all information is still considered approximate.
3 LOD 300: Design Development
Graphical representations of LOD 300 items are similar to LOD 200, but their geometry and physical properties are considered accurate at this point. In other words, the information obtained by the LOD 300 models can be used at the construction stage.
4 LOD 350: Construction Documents
LOD 350 elements contain the same information as LOD 300, but also include interfaces with other building components such as connections and supports. The LOD 350 model indicates how the component will be installed, as well as how it will interact with other building systems.
5 LOD 400: Construction
At this point, the LOD 400 elements include details such as manufacturing, assembly, and installation. Suppliers can use these details and information to manufacture the components that are represented. Invisible information can also be attached to these form elements.
6 LOD 500: As Built
The LOD 500 elements are field verified for size, shape, quantity, location, and orientation, and are considered to be accurate representations of a building’s elements after construction. Facility managers can use these items as a reference for operation and maintenance.
Now that we know about all the 6 LOD’s involved in BIM, the next step is to learn how to use them.
How can the LOD framework be used effectively?
It is important to remember that the Level of Development is a communication tool used to determine the modeling complexity of building elements. It is not necessary to develop the entire model up to 500 LOD per project. For example, standard, commercially available materials and components do not require a manufacturing detail (LOD 400). In some projects, some aesthetic details of the building are determined after construction, which may be left at a preliminary stage (LOD 100 or LOD 200). It is recommended to consult with a technical team with experience in BIM to determine building design requirements. Developers and contractors can save time and avoid unnecessary work by defining the level of control required for building systems.