Sub and specialty contractors are at the workplace every day, so many practical benefits that proponents of BIM claim will arise from its use should translate directly into cost and time savings for them, and they do, but not always, and not to the same degree as advertised. One concrete subcontractor who has spent four years and “invested millions” in developing his own system for producing construction BIM for process planning, and then purchased display technology for taking BIM to the jobsite to prep his crews, has decided the exercise hasn’t been worth it.
“If you know your work well and have processes in place that works, traditional processes and planning work very well. A model, or what they are calling BIM, doesn’t help,” says David Hudgens, president of Accu-Crete, Arlington, Va. “I don’t have much faith in it, and I went all over the world.”
Tow years ago, Hudgens built a sophisticated “I-Room” at his office for model coordination. He started a small company in India to generate construction models from 2D documents and specifications and spent years trying to codify his trade’s best practices, all with the idea of coordinating his crews and those of other trades, like plumbing and framing, and automating as much as possible. “I have been as big a dreamer as anybody,” Hudgens says. “But it’s dressing up a pig. It’s still a pig. We never got any return on our technology efforts; just bled to death.”
The concrete trades are one of the groups not taking up BIM too readily, says Alex Ivanikiw, a senior vice president at Barton Malow Co., Southfield, Mich. The firm has been in the forefront of coordinating subs around BIM and has a feel for the relative rate of adoption.
“The steel fabricators are clearly out in front of all other trades,” Ivanikiw says. “The mechanical and electrical specialty contractors are getting on board, particularly the HVAC and their shop drawing guys. The ones behind the curve are the architectural trades. The concrete, curtain-wall and interiors people are well behind in adopting and implementing BIM.”
Ivanikiw recently surveyed seven subcontractors he has worked with extensively and convinced them to share their metrics on BIM. All of the companies have done at least five BIM projects, and all had contracts of more than $5 million on the jobs involved. Although one firm says it now spends more time on shop drawings, that’s because it plans more thoroughly and saves on materials and installation as a result.
“One mechanical contractor said that using BIM has allowed for more just-in-time delivery to the jobsite, less material handling and less waste,” says Ivanikiw. “They have seen improvements in safety and attribute it to less fabrication on site, less material stored there and less waste to stumble over. They have fewer onsite labor hours, which reduces the exposure to incidents.” Barton Malow and its subs have achieved BIM progress working as design-build teams, sometimes on sequential projects, which helps them accumulate the advantages of lessons learned.
Ivanikiw cites metrics from a pair of very similar plants built for General Motors on adjacent sites in Toledo, Ohio, 18 months apart. The second one is still under construction and will finish next September. Both were done with coordinated 3D design and the same design-build team. By optimizing the process, materials, engineering practices and constructibility planning, Ivanikiw says the team has been able to reduce the cost-per-sq-ft between the first plant and the second by 9.7%.
Bill Zahner, president of architectural metals specialist A. Zahner Co. Inc., Kansas City. says he also is beginning to see some firms using BIM well, while others are “paying lip service.” For those using it well, BIM is opening a feedback mechanism between the trades that can help them coordinate designs and processes. He says one way it is improving the final product is through tolerance control.
“What happens today in the U.S.—and is the reason you see articles in the European press saying the quality of American construction is so [terrible]—is the tolerances are allowed to be handled so loosely in the interface,” say Zahner. “That’s why you see all those big caulking joints and wide flashing. It’s like having a cheap suit. BIM management is about handling all those interfaces.”
In his practice, Zahner says he bases his model on the architectural and structural-steel designs. He then sends his model’s geometry and attachment coordinates back to the steel erector to make sure the elements Zahner fabricates in his shop in Missouri line up with the surveyed reality in the field.
“I am working with one in Doha, Qatar,” he says. “It’s a huge piece of art. The tolerance of the steel structure is 50 millimeters, but the tolerance between that and the art I’m constructing is one-tenth of a millimeter. We are making the connection piece, providing the x-y-z points, and if there is something that doesn’t fit I can make an adjustment in my art. As long as you know it ahead of time, you get the information and plug it back into the model and see what you have to do before it gets real expensive.
“The more we can define digitally the better off we end up being. It takes risk out of offsite fabrication and for assembly planning,” Zahner says.
Dave Morris, director of virtual construction for EMCOR Construction Services, and chair of Associated General Contractors BIM Forum subcommittee, says BIM-managed coordination between the trades and their activities is paying off for everyone.
The obvious benefit for all trades is to perform clash detection between components installed by other parties, he says. Another benefit is to do clash detection in scheduling. “It’s the whole ‘two objects cannot occupy the same space at the same time’ thing,” says Morris. “Construction deals with the final resting of elements, and yes, they end up in different places, but they may pass the same point. So we have to say who goes, and when. We have had a great deal of success with this.”
Morris says Emcor does a lot of its own fabrication and has been able to find qualified subs with compatible software and systems who can work from Emcor’s digital designs. He says there are really relatively few software products being used by each of the trades and fabricators, so compatibility is not much of an issue.
“I would say it never was,” Morris says. “There are people who disagree with me, but it all depends on the way you approach them. You say, ‘This is the direction we are going. If you want me to buy from you, you need to be able to do this too.’ No one gets left behind very long. Those who use that as an excuse are just using it as an excuse.
Morris says a big challenge to achieving BIM’s potential comes from uneven capabilities of participating subs, which is one reason he thinks integrated design and construction is preferable to integrated project delivery. That spreads the risk to all parties and makes the poor performance of one a problem for all. “Just bring all the trades in early enough to ensure constructibility,” he advises. “Contractors are doing spatial coordination while the designers are still designing. There are ways to do that with out full-blown integrated project delivery.”
There also is a way to nudge underperforming subs to model their components, he says. “The challenge is always that which is not put in the model, not what is,” Morris says. “The point where people leave off is where the spatial coordination fails.” Morris says that has led to a recommendation by the AGC’s BIM subcommittee to add a protocol to contracts in an appendix or instruction to bidders that anything a sub decides not to model cannot be installed until all modeled components have been.“For the process to work, all of the items in a spatially coordinated model should be installed ahead of any item that is not in the BIM. If you leave your lights or your boxes out, that’s fine; you just go in afterward,” Morris says.