An inadvertent meeting of the minds during planning for a 484,000-sq-ft hospital in Dayton, Ohio, turned into an effort that has propelled multitrade prefabrication of hospital components to a new level. In the most ambitious U.S. implementation of the strategy, the construction manager estimates that prefabbing the 178 identical patient rooms and 120 overhead corridor utility racks sliced more than two months from construction and 1% to 2% off the cost of the $152-million building, which is 90% complete.

The first effort is seen as just a beginning. “I want to change the design of hospitals with this process,” says Marty Corrado, project executive for field operations in Skanska USA Building Inc.’s Nashville office. Skanska leads a joint venture with the local Shook Construction to build the 12-story Miami Valley Hospital Southeast Addition. “This is going to revamp the entire [hospital-delivery] process as we know it,” says Corrado.

For the job, building team leaders decided, during design development, to join mechanical, electrical, plumbing (MEP) and drywall trades in a warehouse to assemble five levels of racks, bathroom pods and bed “head” walls. “The unique part of this project was combining the MEP in our prefab unit,” Bobby Coyle, executive vice president of drywall contractor Dayton Walls & Ceilings Inc., Dayton.

If the decision to prefab had been made on day one, the team could have cut four to six months from the schedule and still produced a higher-quality building more safely, says Corrado.

As it was, the prefab strategy helped recoup a large part of a 14-week delay, caused by the need to pull out 10 footings and redesign foundations after the discovery of a sandy seam of soil missed during test bores. “They picked up eight to 10 weeks because of the prefab,” says Bob Eling, director of strategic construction for Miami Valley Hospital (MVH), which is owned by Premier Health System.

Multitrade prefab has all the pluses of single-trade prefab: a controlled environment; increased safety by doing typical overhead work, including welding, at bench height rather on ladders; increased productivity, eliminated turf wars and minimized waste. In the warehouse, there were only 18 workers assembling 178 patients’ rooms and 120 racks. There were no shop injuries.

Worker productivity for laying pipe, for example, went up 300% over site-work productivity, while labor costs were down about 20%, says Corrado.

A schedule boost is concurrent prefab and building structure work, without crews tripping over each other. “We built 35% to 40% of the project without even stepping onto the site,” says Bill Riddle, vice president of construction for TP Mechanical Contractors, Cincinnati.

With multitrade prefab, jobsite safety is easier to manage because fewer workers are required, site deliveries and storage needs are reduced, and turf battles are eliminated. In the field, it took an eight-hour work day to install 33 bathroom pods and only 1.5 weeks to rough-in a 30,000-sq-ft patient floor.

To achieve the advantages, the approach requires full-team collaboration, early design decisions and shifts in process and schedule. “The earlier the process starts, the more successful the prefab will be,” says Mark Smith, project manager for the local Chapel Electric Co. LLC.

“Decisions about how the utilities attach to the building frame and decisions about patient-room design had to be accelerated four to six months,” adds Tim Fishking, a principal in the Columbus office of project architect NBBJ.

For multitrade prefab, affected subcontractors need to be brought in about halfway through design development, to offer their two cents on production efficiency and constructibility. Prefab works best under a design-build scenario, but design-assist also works, says Corrado.

On MVH, the meeting of the minds occurred when the topic of prefab came up during a planning session of NBBJ, Skanska-Shook and MVH, on Oct. 18, 2007. Independently,...