Although the firm's investment in model-based estimating has been complex, Wright says Hoar's estimating team saw the value right away, as the team was at that time working on a hard-bid project, using traditional approaches with manual 2D takeoffs. It was a slow go. But after they got their hands on a 3D version of the model, the team discovered complex issues with the foundation they wouldn't have seen working in 2D.
"There were also liquidated damages on the project and the schedule was extremely tight," says Wright. "Rather than spend another two weeks on the project, we decided not to bid."
The firm's senior management was convinced; Wright's group got to work training more estimators on model-based takeoffs.
"What Vico's got is an understanding that [contractors] don't always start with a finished model, especially with integrated projects and other types of work," says Brad Hardin, author of the book "BIM and Construction Management: Proven Tools, Methods and Workflows," which is due to release an updated version in December.
"Since you typically don't begin with a fully detailed model in model-based estimating, you need the ability to build assumptions early into the estimate from whatever information you're pulling from and change this to more detailed information later," he says of using a 3D file. For example, he adds, a contractor might use a model to assign an initial 100,000 sq ft slab a per sq ft cost initially, then later slice that slab into four 25,000 sq ft pours, adding crew size, productivity, materials and other information as more design data becomes available. "Depending on the factors you've built in, you can use the model to build a more accurate schedule and estimate," he adds. "So if eight crew members can get so many yards of concrete put in place a day, we can also see what amount of work a twelve man crew can accomplish as well and still use updated design models to see what's changed," he says. "By contrast, the problem with quantity takeoffs from 2D files, especially on the updates, is that it's really hard to catch what's been updated from one 2D file to another one."
Still, it's early yet to call 5D BIM a widely adopted method, according to research from McGraw Hill Construction, the parent of ENR. Its recent study "The Business Value of BIM for Construction In Major Global Markerts" reported that 82% of U.S. contractors use BIM in multi-trade coordination; 52% use it for visualization of design intent, and 45% use it for constructabilty evaluation, but only 9% are using it to integrate models with cost. In Canada, by contrast, cost integration is one of the larger uses, reported at 31%. The top BIM construction activities and post-construction activities are used by comparable levels of contractors in the U.S. and Canada. The only exception is in managing modeling for owners beyond closeout, where notably fewer contractors in the U.S. report doing this than Canadian ones.
Hardin, who is also the chief technology officer for Leidos' facilities and design build group, sees scheduling and estimating as the next wave of collaboration to shift the industry, which is catching up to other sectors with BIM use. "We need to have these systems talk to each other—especially with BIM when you're dealing with so much information that's available for capturing. But it doesn't necessarily mean that all that information needs to talk with every other system," he says.
"A lot of that has to do with Lean [Product Delivery] thinking," Hardin adds. "Why can't I just extract [data] from my model and then that information gets pushed across all my other systems for estimating?"
