'Prefab' construction moves into mainstream

Prefabrication — a decades-old concept for saving money and time in construction once dismissed as synonymous with low quality — is making a huge comeback in an era when advances in computer-aided design have reinvented the idea into an indispensable tool for some of the biggest commercial building projects.

The "prefab" concept blossomed in the 1950s, when it became shorthand for slapped-together housing erected as quickly as possible to meet the needs of the baby boom generation. For the first time, builders used components that were assembled in off-site workshops and shipped in on trucks in order to mass-produce millions of starter homes across the country.

The results were often less-than-stellar, derided in popular culture as cookie-cutter and soulless — think Pete Seeger's song "Little Boxes."

Skip ahead to 2014, when multimillion-dollar apartment buildings, hospitals, massive data centers and commercial buildings of all types from major builders such as Opus Design Build and Mortenson Construction are incorporating 21st-century versions of prefabrication on a big scale — and turning those negative perceptions on their head.

The builders say that with the adoption of computer technology such as building information modeling (BIM), which allows for 3-D visualization and management of construction projects, and the resulting closer communication between contractors and other team members, tapping prefab parts to save time and money can be accomplished without any drop in quality — in fact, just the opposite.

Opus has extensively used prefabricated wood-frame exterior wall panel sections in the construction of three University of Minnesota-area student housing buildings — Stadium Village Flats, the Station on Washington and the Venue at Dinkytown — as well as on its boutique Velo Apartments effort in Minneapolis' North Loop.

"The use of prefabrication is everywhere now,'' said Tom Becker, Opus Design Build's director of project management. "The reason is that with the projects essentially existing in the computer before they do in the real world, people are able to lay out all the walls, all the openings, basically every detail ahead of time and share it with manufacturers who can produce the components. It injects a layer of quality control that you don't get any other way.''

Mortenson, as well, has been extremely active in incorporating off-site prefabrication in many of its building projects, marking it as a key element in a companywide push for "lean innovation."

The Golden Valley-based company this month published a cost-benefit analysis of the prefabrication techniques it used in the building of the 826,000-square-foot, $400 million Exempla St. Joseph Hospital in Denver, which is scheduled to open in December. It concluded that for every dollar spent on prefab, approximately 13 percent of the investment was returned as a quantifiable benefit to the project.

The use of prefab exterior wall panels, for example, resulted in 3.7 percent of direct savings, while scores of preassembled bathroom pods — made off site and inserted fully made into the building — saved the equivalent of 52 days of construction.

Troy Blizzard, Mortenson's director of operations, said clients are routinely seeking the use of prefab elements in today's market.

"Locally, we're installing preassembled ductwork-and-piping 'racks' in the hallways of a major data-center client we're working with, and we also used that technique on the top floor of the Radisson Blu hotel at the Mall of America," he said.