McGraw Hill Construction, the Lean Construction Institute and Dassault Systèmes teamed up recently to produce a research report on Lean Construction. The following is an excerpt from the report, illustrating how one construction team has benefited directly from Lean practices.
CASE STUDY: Collaborating on Prefabrication to Improve Schedule
Exempla Saint Joseph Replacement Hospital
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Faced with a daunting state-imposed deadline, the new Exempla Saint Joseph replacement hospital project in Denver needed to be on an extremely fast-track path.
To meet the challenge, the project team devised a highly collaborative strategy that leverages multi-trade prefabrication and modularization to shave schedule.
The plan would enable the team, led by Mortenson Construction, to deliver the 831,000-sq-ft facility in 30 months—five months ahead of an estimated traditional schedule.
“Prefabrication had to be a significant part of this strategy,” says Bill Gregor, construction executive for Mortenson. “It was the only way to meet the schedule restrictions.”
Gregor says the team needed to fast-track both interior and exterior elements to keep everything moving ahead quickly. The team focused its efforts on four main elements for prefabrication—exterior wall panels, multi-trade corridor racks, bathroom pods and headwalls. By accelerating the exterior panels, crews could enclose the facility quickly and help the team maintain pace with prefabricated interior elements.
That process was enabled, in part, by the contractual framework. Although the project uses traditional contracting methods, integrated project delivery concepts were implemented. Stakeholders committed to a collaboration agreement, which includes incentives, as well as a BIM execution plan to map out the process.
Collaboration proved critical. To accelerate the schedule, designers and contractors worked together in the schematic phase—or earlier—to minimize redrawing.
“Early on we had prefabrication charrettes,” Gregor says. “There were brainstorming sessions with a lot of the players involved to work through all of the ideas of what we could accomplish.”
Prefabrication and Modularization
For the enclosure system, Gregor says a joint venture of two local contractors were brought in during the design development process, allowing the design team’s work to be informed by the prefabrication process. “[The design team] drew it knowing how we would fabricate [the panels] so they could create modules in their drawings.”
Contractors prefabricated 346 exterior panels—most of which measure 30 ft. by 15 ft.—at a warehouse within five miles of the project site. Five to six panels could be brought in per truck for just-in-time delivery. Each panel was picked directly from the truck, lifted and installed. “On our best day, we placed 26 panels,” Gregor adds.
To help expedite the hospital’s 640 bathrooms, the team decided to create 440 of them as modular pods. The original design included 75 different bathroom configurations, but the team was able to rework it to establish 15 standardized pods. The custom pods were designed to a schematic level and then handed off to the manufacturer. “The manufacturer drew it, designed it in the model and transmitted it back to the design team as an element to insert into [the design] model,” Gregor explains.
One of the more unique aspects of ￼the team’s overall approach is the use of multi-trade corridor racks. Only a few hospital projects had used this technique prior to the Saint Joseph’s job, but Gregor says Mortenson saw significant potential given that schedule was a primary driver. The 166 corridor racks, which measure roughly 25 ft. long, were constructed in a rented warehouse close to the site. Although each rack contained unique elements, the team worked to standardize and streamline the design as much as possible to improve efficiency.
Mechanical and plumbing contractor U.S. Engineering took the lead, first building the steel structure, then adding ductwork, piping and related elements. The racks were on wheels, enabling crews to move them from station-to-station within the warehouse. After U.S. Engineering’s work was done, the rack was moved over to the electrical crews from Encore Electric to add their work. From there, insulation, drywall and framing were also added.
Dan Strait, vice president of project development at U.S. Engineering, says that compared with traditional methods, the multi-trade racks required significantly higher levels of collaboration and coordination, particularly in terms of logistics and constructability. “How do you, from a constructability standpoint, connect a rack to the lower wall sections?” Strait says. “From a logistics standpoint, how does that workflow go? Is it a benefit or not? There are a lot more conversations like that.”
Strait said the trades created digital models for coordination and fabrication. U.S. Engineering could also generate a bill of materials for each rack as well as a set of instructions for crews from its models.
The team also created a production schedule that allowed for a steady flow of racks. Strait says crews created the racks slightly ahead of construction, storing up to two weeks of racks in the warehouse. By using this method, Strait says contractors could maintain steady manpower needs, avoiding peaks and valleys. By allowing some limited storage, the team could accommodate for fluctuations in field installation.
Once shipped to the field, crews could install up to five units per day, creating roughly 125 feet of corridor space.
For the final piece of Mortenson’s strategy, the team is creating 376 multi-trade headwalls, which include piping for medical gases, electrical, framing, drywall and finishes.”
The project, which topped out in April 2013 and is scheduled to be completed in late 2014, is ongoing and Mortenson does not have final metrics in place, but clear benefits are emerging.
As of October 2013, the project was a month ahead of schedule, five months ahead of a traditional schedule. Gregor also notes that, with so much prefabrication being done in warehouses at ground level, the work is exposed to much less risk. There were no recordable incidents on the prefabricated work, as of October 2013. Gregor notes that in some ways elements, such as the multi-trade racks can cost more in terms of direct costs, but that it is made up in other ways, such as reduced overall schedule. “We’ve been able to identify that it is cost-neutral,” he says.
Strait says he also sees significant benefits to the schedule. U.S. Engineering and Encore Electric partnered on multi-trade rack corridors for another project in Denver that completed this year, and they were able to build upon their collaboration in this project and work together effectively. He says that the team was able to install corridors on that project in one third of the time it would take for a traditional job.
“It’s a great concept,” he says. “The collaboration is a benefit in itself. It brings the team closer from both a cost and construction standpoint. You get just as good quality, if not better, and it’s leaner construction in terms of workflow.”
SOURCE: McGraw Hill Construction SmartMarket Report, “Lean Construction: Leveraging Collaboration and Advanced Practices to Increase Project Efficiency”