... behaviors are, argues the Seattle-based virtual design and construction team of Skanska USA Building.

More and more contractors are using BIM for 4D model-based scheduling and 5D model-based estimating. For 5D, some contractors hire full-time modelers from the design world. That enables better coordination with designers, says James P. Barrett, Turner’s regional manager of virtual construction technologies.

But it can blur the line between design and construction. “We accept this ambiguity for now because in a BIM ‘world order,’ it is critical that we have the same tools as a designer so that we can accept and disassemble design models for integration into BIM-based estimating,” says Barrett.

Part of the challenge with 4D is the shelf life of the 4D model. As construction progresses, the schedule and model need to keep pace. “For this, we need someone on the site to be continuously updating the 4D models based on our weekly work plans,” says Atul Khanzode, director of virtual building in the Redwood City, Calif., office of DPR Construction Inc.

Khanzode says DPR needs more detail and data for 5D than a designer normally puts in a model. Collaboration with the design team is needed for this.

Rodd Merchant, vice president of engineering services and design-build for JE Dunn Construction, Denver, says interoperability with project-management and accounting software is very important and largely nonexistent. “I see our field engineers calculating units, volumes, etc., by hand all the time,” he says.

Larson says getting contractors and designers to follow the same protocols in different submodels, so that the contractor can integrate them, also is a continuing challenge.

Contractors realize they have only tapped the surface of BIM-enabled construction. With the right information they can visualize and track other project data, such as submittals, requests for information and change orders.

Builders that have invested big bucks in BIM say it is difficult to pinpoint cost savings that result from virtual construction, mainly because the focus is on cost avoidance. That said, anecdotal results on PCL projects show that for every dollar spent, PCL gets $2 to $3 back, says Hoagland.

But there still could be a wrench in the BIM works. “Risk and professional liability are huge issues that lurk,” says Kevin M. Bredeson director of the north central regional office of Gilbane Building Co., Milwaukee. One insurance lawyer advises builders to purchase a contractor’s professional policy that includes BIM-related services.

Risks aside, some are pushing to the next frontier: Going directly from design BIMs to computer numerically controlled fabrication of building systems.