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Prefabrication in Practice

Weighing the advantages against the challenges


After years of promise, prefabrication and modular construction are finally being used to tackle large construction projects at scale.

Proponents of prefabrication have long lauded that prefabbed construction yields better, cheaper and faster construction, as projects can essentially be built in a controlled environment. This allows contractors to avoid delays caused by weather and unforeseen conditions, and allows the bulk of assembly to be performed away from the construction site, avoiding space constraints. These advantages often result in cheaper labor costs due to a variety of factors. Adoption has been slow however, due to transportation costs, initial startup costs, insurance concerns, and fear of labor disruption. Nonetheless, the industry is now seeing prefabrication grow on work from prefabricated electrical panels to curtain wall systems, both of which involve repetitive elements that can be made more efficiently in a factory environment and then inexpensively transported to the project site.

So what are prefabrication and modular construction? Prefabrication refers to building elements that are manufactured and built using assembly line processes, typically off-site. Modular structures on the other hand are a subset of prefabricated structures comprised of repeating sections called “modules.” The repetitive structures allow for easy on-site assembly, where modules can be stacked like LEGOs. Generally, prefabrication brings advantages to the construction process in the form of shorter build times, controllability, and efficiency.

While modular and prefabricated constructions comprise about 3 percent of construction in America, labor shortages in the construction industry and the need for affordable housing are sure to drive this number higher. For instance, New York City’s Department of Housing Preservation and Development required modular construction in the RFP for its recently announced plans to develop a 167-unit affordable housing building in East New York. The $70 million project would be the first under Mayor Bill de Blasio’s Housing New York 2.0 plan to increase the city’s affordable housing stock to 300,000 units by 2026. This number makes up about 10 percent of the 3.5 million units currently available. While cities have employed prefabrication techniques in the past to address housing shortages, such as Los Angeles’ 102-unit Star Apartments homeless shelter and New York’s 55-unit Carmel place micro-apartments, de Blasio’s plan marks the first large-scale public endorsement of these techniques.

Another driver for prefabrication is sustainability. Last September, Amazon invested in Plant Prefab, a Southern California startup, and officially entered the sustainable and smart home marketplace. Offsite construction offers advantages through reductions in material waste, economies of scale, quality control processes, and efficient scheduling. As prefabrication techniques become more common, adoption will likely be particularly pronounced in areas where weather is frequently an issue.

Despite the advantages of modular building, critics have cited weaknesses with this approach, including: transportation and storage, difficulty arranging architect check-ins, replicating errors, and thicker floors. Since structures are built off-site, manufacturers must coordinate with local transportation authorities to use the roads, bridges, and tunnels, and then block off the site for cranes and other rigging equipment. The off-site construction can also impose burdens on the design teams’ need to assure compliance with the plans and specifications, especially if the builders are located in another country.

The ability to “build” in a controlled environment often allows prefabricated work to be stronger and allows for tighter tolerances than on-site constructions. However, minor errors in design can prove catastrophic in prefabrication, where error detection in installation occurs at a later stage, after multiple prefabricated units have already been manufactured. Nonetheless, as Building Information Modeling (or BIM) becomes more advanced and widespread, conflict concerns are reduced as computer modeling can often prevent such issues from occurring.

Historically, prefabricated homes were used successfully in the past to fuel westward expansion during the Gold Rush and provide affordable housing to World War II Veterans. Today, these techniques have already been used to construct chemical plants, China’s 57-story mixed residential and office tower, Mini Sky City, and Marriott’s 97-room Folsom Fairfield Inn & Suites. Now, large companies and governments alike are promoting the use of modular building techniques and see it as a way to keep up with housing demand. Only time will tell, however, if the promised cost and time-savings of these projects will outweigh their logistical difficulties.

Kenneth E. Rubinstein is an attorney and co-chair of the Construction Law Practice Group in the Boston, Massachusetts and Concord, New Hampshire offices of Preti Flaherty Beliveau & Pachios, PC, an AGC of Massachusetts member. David Kim is a law student at Boston University School of Law (graduation anticipated 2020).