LOD Specifications to help BIM go mainstream as collaboration tool
The first industry standard to specify the content and reliability of Building Information Models (BIMs) as a collaboration tool at various stages in the design and construction process is now a reality as the BIMForum, a national group of AEC professionals using BIM, just rolled out its 2013 Level of Development (LOD) Specification for Building Information Models.
“This is going to be a big, big industry document,” John Russo, CEO of Architectural Resource Consultants, BIMForum member, and president of the U.S. Institute of Building Documentation, which is spearheading industry efforts to grow the adoption of 3D imaging in the AEC sector, told SPAR. “It is going to become one of the guiding standards out there.”
Addressing the need to specify a level of accuracy in order to provide consistent expectations throughout the building lifecycle – from planning through design and construction – LOD specifications define BIM elements of different building systems at different levels of development.
The idea is to promote the LOD framework and standardize its usefulness as a communication tool, since it is necessary for BIM users to know when information will be available in order to plan their work.
The framework helps address several issues that come up when a BIM is used as a communication or collaboration tool, basically, when someone other than the author extracts information from it.
During the design process, building systems and components progress from a vague conceptual idea to a precise description. In the past, there has been no simple way to designate where a BIM element – such as a light fixture – is along the way.
In a BIM, a generic element placed approximately can look exactly the same as a specific element located precisely. That’s why clear definitions for model elements – not just appearance – are necessary to provide for clarity in a BIM.
The LOD specs allow BIM authors to define what their models can be relied on for and allow other users to understand the value, and limitations, of models they receive.
“We want everyone to have the same understanding about how much information should go into each element of a building model, and for what uses those models are suitable,” said Dmitri Alferieff, BIMForum director. “This specification will eliminate much of the confusion that comes with having different expectations for what should be in the models. The LOD specs “provide a good framework for project team members to specify what kinds of information they want in a model and, essentially, labeling a model in terms of what is in there.”
The BIMForum licensed LOD definitions, developed by The American Institute of Architects (AIA) in 2008, for its new LOD framework.
BIM has been outlined into five levels – LOD 100-500, which describe the levels of development of a BIM model. The higher the number, the higher “the degree to which the element’s geometry and attached information has been thought through – the degree to which project team members may rely on the information when using the model.”
- LOD 100 – Basically, the equivalent of conceptual design. The Model Element 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.
- LOD 200 – Similar to schematic design or design development. 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.
- LOD 300 – 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. Model elements equivalent to traditional construction documents and shop drawings.
- LOD 350 – The Model Element is graphically represented within the Model as a specific system, object, or assembly in terms of quantity, size, shape, orientation, and interfaces with other building systems. Non-graphic information may also be attached to the Model Element.
- LOD 400 – This level is considered suitable for fabrication and assembly. 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.
- LOD 500 – This level represents the project as it has been constructed including as-built conditions. 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.
For now, the BIMForum has decided not to tackle LOD 500, which is meant for facility management and operations. Alferieff said building owners currently employ “a variety of different approaches” using BIM to manage and operate facilities, making it difficult to standardize.
So, BIMForum decided it was beyond the initial scope of the standard to address all of them, leaving the definitions it developed for LOD Specifications to address model element geometry with three of the most common uses in mind:
- quantity take-off
- 3D coordination
- 3D control and planning
Alferieff said leaving LOD 500 on the back burner in no way diminishes the new LOD guidelines.
“You can still track existing conditions,” he said. “The owners are still getting as-built models. They’re just not using the model for active [building]management. But, I think that is taking shape.”
BIM goes mainstream
BIM has gone mainstream for the North American construction industry with adoption expanding from 17 percent in 2007 to 71 percent in 2012, according to McGraw-Hill Construction’s SmartMarket Report, “The Business Value of BIM in North America: Multi-Year Trend Analysis and User Ratings (2007–2012).”
“From my vantage point, as a service provider, I’m watching the AEC market explode with 3D,” said Lou Bush, client account manager at Calabi Yau Systems and a 35-year veteran of the surveying industry. “I have seen a big increase in scanning and using it on projects for the first time. It’s happening everywhere.”