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LEVEL OF DEVELOPMENT (LOD) CONCEPTS
The American Institute of Architects has developed a system for use in contracts that defines responsibilities and authorised uses for Building Information Model (BIM) models.
This is necessary for two reasons:
In a proper BIM model information is created by one party only, and not duplicated by other parties. It is important to identify who is responsible for what information.
The degree of completeness and accuracy of a computer model is not always obvious because by its very nature digital information is precise. It is important that the uses this information can be safely used for is defined.
In reality these reasons are not unique to BIM. It would be useful for any delivery method to clearly define who does what.
Typically this approach would be used for agreements between consultants, the same document ("Exhibit" in USA legal jargon) being included in all consultant agreements for a project.
It could also be used in agreements with clients, particularly contractor clients after novation.
The system is basically a matrix that introduces a new concept, Level of Development (LOD). This is a concept that describes the degree of completeness of a parts of a BIM model.
LODs are defined in a range from LOD 100 to LOD 500. Each LOD series can be further divided into finer grain detail if required.
Subsequent LODs includes the degree of development of all prior LODs.
Each LOD is defined by describing Model Content Requirements and Authorised Uses for the model (see below).
Model Element Author (MEA) is the author for each LOD.
By combining these two concepts with a list of Model Elements (parts of the building) and Project Stages,
the matrix is created outlining responsibilities and usefulness of the model.
Example of AIA Document E202-2008 Model Element Table.
As an established protocol we should get in to the habit of talking in terms of LOD.
When talking to consultants, when talking to clients, when talking to team members.
It provides a clearer way of describing what is expected and what is being provided.
Level of Development (LOD)
There are 5 basic levels of development. Although LODs are analogous to traditional design stages,
they are applied to parts of the building, not to the whole building.
LOD 100 - Essentially the equivalent of conceptual design, LOD100 elements consist of overall building massing.
Downstream users are authorized to perform whole building types of analysis (volume, building orientation, cost per metre, etc.)
LOD 200 - Similar level of detail to schematic design or design development, the model would consist of "generalized systems or assemblies with approximate quantities, size, shape, location and orientation."
Authorized uses would include "analysis of selected systems by application of generalized performance criteria."
LOD 300 - Model elements are suitable for the generation of traditional construction documents and shop drawings.
As such, analysis and simulation is authorized for detailed elements and systems.
LOD 400 - This level of development is considered to be suitable for fabrication and assembly.
The MEA for this LOD is most likely to be the trade contractor or fabricator as it is usually outside the scope of the architect's or engineer's services.
LOD 500 - The final level of development represents the project as it has been constructed - the as-built conditions.
The model is suitable for maintenance and operations of the facility.
Definitions taken from AIA Document E202-2008, Building Information Protocol Exhibit.
For further discussion go to LOD explained.
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