Prefabrication: an Important Force in Boosting Worker Safety

Prefabbing components offsite has the side benefit of averting some accidents. 


Prefabrication can speed up projects and save money — big wins indeed. But there’s another major advantage: increased safety.

In a recent 2017 Dodge SmartMarket report on safety management in the construction industry, 83 percent of architects surveyed said they work with general contractors and key trades before completing schematic designs to identify opportunities for prefabrication at least occasionally.

Contractors can have more, and earlier, input on the design — and push for prefabrication when it makes sense — with project delivery methods such as Integrated Project Delivery (IPD) or Design/Build (D/B).

A case study in the Dodge report demonstrates how prefabrication can contribute to worker safety. It describes the construction of an 831,000-square-foot, 360-bed facility for St. Joseph Hospital in Denver.

Safety wasn’t the driving force when the project team decided to prefabricate many building components offsite; they were more concerned with getting a project that would typically require 36 months done in 30 months. But post-project analysis by the project’s construction manager, Mortenson Construction, showed the choice likely averted seven safety incidents.

According to William Gregor, the company’s vice president of operations, “Hallways were less crowded, there were fewer lifts on the exterior and interior of the building and significantly less material, noise and dust.”


“Recordable injury rates plummet in a warehouse compared with the construction site, and every labor hour diverted to the warehouse reduces the probability of a safety-related incident.”

Mortenson Construction's Post-Project Analysis Conclusion

To estimate the number of safety incidents averted, the project managers figured the typical ratio of safety incidents to labor hours and applied it to the more than 150,000 labor hours that were diverted offsite. While a company might expect seven safety incidents during 150,000-plus labor hours onsite, Mortenson Construction had no safety incidents during the offsite fabrication time.

Components prefabricated included 440 bathroom pods, 250 exterior wall panels, 376 patient room headwalls and nearly a mile of multi-trade utility racks (which eliminated overhead work and site congestion in main corridors).

Prefabricating the bathroom pods — which required significant coordination among the owner, design team, supplier and construction manager — diverted 78,000 hours of labor offsite. For the exterior wall panels, the project team used building information modeling (BIM) to design a lifting apparatus into the panels to make installation easier. Workers built the wall panels on elevated tables in a warehouse.

Only the detailing of connections between panels was done onsite. According to the report, “This enabled the building to be closed in much faster than usual, eliminating fall hazards sooner and enabling interior work to begin in a protected environment.”

Mortenson’s post-project analysis concluded, “Recordable injury rates plummet in a warehouse compared with the construction site, and every labor hour diverted to the warehouse reduces the probability of a safety-related incident.”

Noted the Dodge researchers, “Prefabrication, often chosen for its advantages for schedule, quality control or logistics, is also one of the most effective strategies for PtD [Prevention Through Design]. Compared to onsite construction, prefabricated building components in a warehouse provides safer conditions through reduced congestion, better ergonomic positions, environmentally controlled spaces and reduced schedule demands.”

It’s little wonder offsite construction is becoming a shining star in the construction of certain types of buildings. Yet another benefit of prefabrication: In today’s tight skilled labor market, the use of prefabrication may mean fewer skilled laborers required.


Freelance writer Mary Lou Jay writes about business and technical developments in a variety of industries. She has been covering residential and commercial construction for more than 25 years.

Image Credit: Thanate Rooprasert /


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