Contractors have no way of knowing whether they can rely on the designer's LOD 300 information for layout in the field, for example. For the LOD spec, "we tried to be specific per element, regarding what is required and what is the level of reliability," says Reinhardt.

Dellaria's intent, after E202 was released, was to clarify it for Astorino's architects. He started by developing a user's guide for Astorino's staff.

"E202 is a blank matrix," says Dellaria. "I wanted to graphically define the various levels of model progression for universal use, much like the old AIA Architectural Graphic Standards."

For continuity, the LOD spec is based on the AIA's basic LOD definitions and organized by CSI Uniformat 2010. It contains graphic examples as well as text. The spec is divided into four categories of elements: structures, exterior skin, interior construction and building services.

The document does not include LOD 500. But it adds LOD 350, which is specifically for cross-trade coordination.

"Most litigation is between 300 and 400 because that's where most of the money is spent," says Will F. Ikerd II, a principal of IKERD Consulting LLC, Dallas, and a group member.

In addition, the levels are described slightly differently than in E202. The LOD spec descriptions will allow the spec to be used with all delivery approaches, including the more collaborative integrated project delivery and design-build.

"In the long term, I would imagine this document is going to be very important in defining scope, schedule and estimating," says Ikerd, a structural engineer whose firm models all disciplines for trade contractors.

So far, more than 1,000 people have downloaded the draft from bimforum.org/lod/. To date, 85% of respondents have indicated they have experienced situations in which the model deliverable was not adequately described or communicated, and 93% say they are planning to use the LOD spec.

The spec is envisioned as a living document that will be updated. The working group's next big project is to define LOD 500 elements for BIM use in facilities management. For that, the group will expand to include owners.

"Everyone in the working group understood that difficulties [on a project]have more to do with sociology than technology," says Ikerd. "The challenge is communication."