BIM 101 – BIM LEVEL OF DEVELOPMENT (LOD) EXPLAINED

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WHAT IS LOD?

In over simplified terminology Level Of Development (LOD) determines (arguably) how much information is modelled in the 3D file and what data is accessible. Technically, Level Of Development (LOD) is a set of specifications that gives professionals in the AEC industry the power to document, articulate and specify the content of BIM effectively and clearly. Serving as an industry standard, LOD defines the development stages of different systems in BIM. LOD was primarily developed by The American Institute Of Architects and a number of participating organizations.

FUNDAMENTAL LOD DEFINITIONS

By specifying a Level of Development (LOD) it allows professionals in the industry to articulate how an element’s geometry and associated information evolves throughout the entire process. It signifies the degree to which different members of the team can rely on information associated with an element. Following is a definition and explanation of the six (6) Levels of Development that we currently use:

LOD 100 – Concept Design

The building 3D model is developed to represent the information on basic level. Thereby, only conceptual model creation is possible in this stage. Parameters like area, height, volume, location and orientation are defined.

The Model Elements may be graphically represented in the Model with a symbol or other generic representation, but does not satisfy the requirements for LOD 200. Information related to the Model Element (i.e. cost per square foot, tonnage of HVAC, etc.) can be derived from other Model Elements.

Basically, LOD 100 elements are not geometric representations. Examples are information attached to other model elements or symbols showing the existence of a component but not its shape, size, or precise location. Any information derived from LOD 100 elements must be considered approximate.

LOD 200 – Schematic Design

A general model where elements are modelled with approximate quantities, size, shape, location and orientation. We can also attach non- geometric information to the model elements.

The Model Element is graphically represented within the Model as a generic system, object, or assembly with approximate quantities, size, shape, location, and orientation. Non-graphic information may also be attached to the Model Element.

Basically, at this LOD elements are generic placeholders. They may be recognizable as the components they represent, or they may be volumes for space reservation. Any information derived from LOD 200 elements must be considered approximate.

LOD 300 – Detailed Design

Accurate modelling and shop drawings where elements are defined with specific assemblies, precise quantity, size, shape, location and orientation. Here too we can attach non- geometric information to the model elements.

The Model Element is graphically represented within the Model as a specific system, object or assembly in terms of quantity, size, shape, location, and orientation. Non-graphic information may also be attached to the Model Element.

Basically, the quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modelled information such as notes or dimension call-outs. The project origin is defined and the element is located accurately with respect to the project origin.

LOD 350 – Construction Documentation

LOD 350 includes model detail and element that represent how building elements interface with various systems and other building elements with graphics and written definitions.

The Model Element is graphically represented within the Model as a specific system, object, or assembly in terms of quantity, size, shape, location, orientation, and interfaces with other building systems. Non-graphic information may also be attached to the Model Element.

Basically, the parts necessary for coordination of the element with nearby or attached elements are modelled. These parts will include such items as supports and connections. The quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modelled information such as notes or dimension call-outs.

LOD 400 – Fabrication and Assembly

Model elements are modelled as specific assemblies, with complete fabrication, assembly, and detailing information in addition to precise quantity, size, shape, location and orientation. Non- geometric information to the model elements can also be attached.

The Model Element is graphically represented within the Model as a specific system, object or assembly in terms of size, shape, location, quantity, and orientation with detailing, fabrication, assembly, and installation information. Non-graphic information may also be attached to the Model Element.

Basically, an LOD 400 element is modelled at sufficient detail and accuracy for fabrication of the represented component. The quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modelled information such as notes or dimension call-outs.

LOD 500 – As Built

Elements are modelled as constructed assemblies for Maintenance and Operations. In addition to actual and accurate in size, shape, location, quantity, and orientation, non-geometric information is attached to modelled elements.

The Model Element is a field verified representation in terms of size, shape, location, quantity, and orientation. Non-graphic information may also be attached to the Model Elements.

Basically, LOD 500 relates to field verification and is not an indication of progression to a higher level of model element geometry or non-graphic information, it is simply an As-Built model.

WORKING THROUGH THE BIM WORKFLOW WITH LOD

If you look at the diagram below it gives a good graphical representation of what LOD to use where in the BIM workflow process.

EXAMPLES OF OBJECTS MODELLED AT DIFFERENT LOD’S

Example One – A Light Fixture

• LOD 100 – cost/sf attached to floor slabs
• LOD 200 – light fixture, generic/approximate size/shape/location
• LOD 300 – Design specified 2×4 troffer, specific size/shape/location
• LOD 350 – Actual model, Lightolier DPA2G12LS232, specific size/shape/location
• LOD 400 – As per LOD 350, plus special mounting details, as in a decorative soffit

Example Two – A Structural Column with Base Plate

• LOD 100 – basic overall shape / “box”
• LOD 200 – generic / approximate size / shape / location
• LOD 300 – specific size / shape / location
• LOD 350 – actual model including base plates / shape / location
• LOD 400 – As per LOD 350 plus mounting details, model/assembly details and information

GREAT REFERENCE MATERIAL ABOUT LOD

Level Of Development (LOD) Specification Part 1 & Commentary 2019 Manual

The BIM Forum has a great PDF manual: Level Of Development (LOD) Specification Part 1 & Commentary 2019.

It goes into great detail about LOD and gives many examples of how it is applied to different objects…including the Structural Column and Base Plate I mentioned in “Examples of Objects Modelled At Different LOD’s”.

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Natspec BIM Paper – BIM and LOD (NBP 001)

If you are based in Australia and do not know who Natspec is….NATSPEC is a national not-for-profit organisation that is owned by the design, build, construct and property industry through professional associations and government property groups. NATSPEC’s objective is to improve the construction quality and productivity of the built environment through leadership of information. They put together a paper in November 2013 that goes into great detail about LOD, and also includes great examples to give you a better understanding about LOD.

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