What is “LOD?”
First, let’s get our terminology straight. According to the AIA E202 document, LOD is defined as “level of Development.” It does NOT mean “level of Detail;” this is an important concept. Unfortunately, the choice of words makes for increased confusion over the acronym, but there definitely is a difference.
Level of Detail is the amount of information and geometry provided by the content author or other project participant. There can always be a higher level of detail in a project model than what is realistic to be used by others in a downstream workflow. Level of Development is the maximum amount of information and geometry that is authorized for use by others.
Expressed in different terms:
Level of DETAIL = amount of actual information
Level of DEVELOPMENT = amount of usable information
No Such Thing as an “LOD### Model”
LOD is based on assemblies – NOT entire models. The easiest way to understand this is to separate the milestone deliverables from your thinking about LOD’s. In other words, don’t think that schematic design = LOD100; design development = LOD200; and so on.
At any given project milestone, you will likely have a combination of LOD’s. For example, at the end of construction documents, the interior walls and doors might be at LOD300, furniture is at LOD200, and information about electrical fixtures is only supplied as an allowance per square metre; thus LOD100.
The list below simplifies the concept of authorized uses. Essentially, what you should be able to do with an object given a certain amount of input information:
LOD100 = Discuss it (interpolated calculations & estimates)
LOD200 = Specify it
LOD300 = Price it
LOD400 = Build or install it
LOD500 = Operate or maintain it
Note that the design team usually only provides information up to LOD200, or LOD300 for items fully documented.
Does LOD Imply Time?
Another misconception about LOD is that it implies an ‘in progress’ state of content. For example, you might think that LOD200 means that you are placing manufacturer-specific content in your model, but you are still in an early phase of design such that quantities and locations are not finalized. In this case, the correct LOD assignment would be LOD100 with the understanding that at design milestones quantities and locations will be in flux.
Design Intent
Projects that will be competitively tendered – what LOD would you use for final construction documents? Specifications for bid projects usually allow for (or require) a list of alternate products. As such, even if you are using a model component provided by a specific manufacturer, the level of development (reliability) can only be at a generic level – LOD200.