Wednesday, 6 June 2012

LOD = Level of Development

This is kind of a repost of an earlier Blog on understanding the Levels of Development.
BIM Level of Development as outlined by the AIA. Even though it's American standards they have done a lot of research on this subject so it's defiantly worth taking a look and modifying it to your specific needs.

The reason I'll discuss this subject is that as we use Revit more and more we at risk of Over Modeling our model. Over modeling will reduce your efficiency of your workflow as well as the efficiency of your model. We work hard to make Revit work for us but we are in danger of getting sucked into the Void of Over Modeling....
Here is a brief explanation of Level of Development (LOD):

Level of Development: Levels of Development (LOD) describe the level of completeness to which a Model Element is developed.
How much we model at each stage is broken down into 5 basic levels.

LOD 100 - Conceptual Design and Master Planning, creating mass models for the concept stage. Volumes, height, location and orientation, basic building analysis etc. This model can be quickly and easily be analyzed for energy consumption to help make design changes and approval for design options.

LOD 200 - Schematic Design/Design Development. Developing the general assemblies, rough sizes and placement of rooms etc. Here you have the general idea on the design but do not have the specific information on exact wall assemblies or component types. This LOD is typically the basis for the working drawings.

LOD 300 - Working Drawings, Shop Drawings, construction documentation, building analysis, shop drawings etc. Not everything needs to be modeled during this level of development, you can place in your model placeholders which can be specified in the Spec documentation outside of the Building model.

LOD 400 – Fabrication and Assembly  typically not achieved by the Designer or Architect as this level of detail is typically required by fabricators, for example manufacturers of RTU's would detail their components at this level for fabrication of their components.

LOD 500 - As Built Model, Maintenance and Operations, the final level of detail that represents the true building. Ideally used for building operations and maintenance. Typically includes extensive information within the model on each component, for example a light fixture may have the wattage, warrantee information, the suppliers contact info, model number etc…

Model Elements: Model Elements represent building component, system or assemblies within a building or building site.

Model Element Author: The party responsible for developing the content of the specific model. To the Level of Detail required by the particular phase of the project.

Model User: this refers to any authorized individual or company who may use the model. For example someone doing a quantity take off, scheduling, analysis?
So... LOD... Level of Development how does this affect the typical Revit User?

In the old 2D drafting days we would draw lines to represent objects such as walls doors, windows roofs etc... remember that? We use to draw two lines representing a complete (and often complex) wall assembly. Often these lines didn't even represent the true dimensions of the assembly either!
Drawings got done and buildings still got built.! Amazing times.....

Now with BIM were adding more information to our drawings by adding more information to our Building Information Model. For the majority of us the end result is a set of documents that someone can build from. Don't lose sight of that, we are in danger of Over Modeling....

We get so wrapped up in creating content and families for everything that sometimes we loose sight of why we are creating this model in the first place. Remember your creating drawings within a specific time limit. If you go over this time limit you are burning up the profit margin, when we first are introduced to Revit we think to ourselves "wow, this is going to save me a bunch of time", "I no longer have to draw elevation, sections" etc... however my experience is that we get seduced by Revit and we want to build a complete model down to the nuts and bolts.

We need to model what is appropriate to the project. If your doing a residential home do you really need to model the gutters and drains? Do you need to model the gas meter on the side of the house? For larger projects do you need to model the tactile strip at the top of the stairs? Would detail lines in the view be sufficient. There is a huge difference in resources between the two. Do you need to use the roof top mechanical unit from the supplier that is detailed down to the nut and bolt? Why not use a generic placeholder.

Try to use families that are smaller in file size this will help your project file size to stay manageable.
So try and stick to a LOD of 300 (Precise Geometry) instead of LOD 400 (Fabrication)......


  1. Don't forget Revit mep is only about a level 200 maybe 250 drawing tool. it can create part of the 300 level but not all generic parts are too loose to really coordinate true space needs the true coordination falls to the contractors still just as it did in the days of 2 line drawings. Many engineers are thinking that they are creating a level 400 coordinated and ready to fabricate. Revit Cannot create this level of accuracy.

    1. provides content that allows Revit MEP LOD 400 modeling.

  2. I have reviewed for the BIMForum 2015 LOD Specification, including its errors, omissions, what works, what does not, and how to deal with the issues

    I hope your readers will find it helpful following your above detailed article and maybe answer some of their questions.