The Ideal Time for Prefabrication
Prefabricated concrete is used for both architectural and structural applications on all types of buildings, from low to high rise. And it isn't new. Prefabricated construction has been around for over 50 years. Yet still, misconceptions have led to architects, engineers, general contractors and owners missing out on the benefits and full potential of prefabrication and off-site manufactured construction.
The perception that prefabricated building systems hinder design and compromise quality has stifled adoption in our country and created a stigma, but the tide is turning. Outside factors such as the skilled labor shortage, tight schedules and budget overruns are impacting the industry. At the same time, owners and especially owner-occupiers, increasingly expect a design and construction process that is efficient, productive and cost effective to a degree that traditional construction methods can't deliver. So what's the answer?
Architects, engineers, general contractors and owners who have experienced the benefits of prefabrication firsthand and once were skeptics, now champion its scheduling, quality and cost benefits. Yet still, there are hurdles. When most design teams or owners think about prefabricated construction, they aren't thinking about the structure. Instead, the first things that come to mind are bathroom or kitchen pods that require more transportation and added installation costs. However, by leveraging a prefabricated concrete slab as a framework for which you can then add on prefabricated kitchen and bathroom components in a factory setting, the entire unit can be shipped, without added costs or the need for additional transportation.
When the structure is prefabricated, the cost savings, efficiency gains and reduced risk can be tremendous. It becomes easy to off-site other elements of the project because the structure provides the work surface for additional trades to work from. The tempo and crew size is often based upon the consistency of the structure being delivered so that other trades can work. By making the structure available in a consistent timeframe, it allows other trades to size their crews efficiently and stabilize the work patterns and locations on a jobsite.
Provides Labor Cost Certainty and Solves Problems Related to the Skilled Labor Shortage
With a labor shortage among us, prefabrication enables work to be done by fewer, highly skilled workers. Off-site construction allows skilled craftsmen a safer and more productive place to do their job and quality can be monitored throughout the production process.
Off-site construction can deliver a project between 30 to 50 percent faster than traditional methods because construction of the building occurs simultaneously with the site and foundation work. Schedule delays due to weather and other external factors are a non-issue given that the build takes place in a controlled environment. In fact, 72 percent of contractors surveyed by McGraw Hill stated that the use of prefabrication decreased project schedules by more than a week, and 37 percent stated it reduced the schedule by four weeks or more.
Delivers Early Cost Certainty
Often, for the prefabricated portion of a project, the initial cost is the final cost. By engaging in the design process early, the project design team and other key players align on project requirements from the beginning. This collaboration and transparency gives all parties visibility into factors affecting the bottom line of a project's budget.
In addition to reducing risk around cost and schedule, off-site construction helps create a safer job site. In a recent study, Safety Management in the Construction Industry, 49 percent of firms using prefabricated or modular construction found it improves site safety. In general, they felt the three main safety benefits of the modular building process were the ability to do complex assembly at ground level, have fewer workers on-site and for less time, and to limit the number of tasks that need to be completed at great heights.
Reduces Site Impacts
Prefabricated building systems bring significant reduction in job site disruption - not only the construction site, but to the neighboring communities as well. Fewer man-days on site means increased jobsite safety, less construction traffic, fewer staging areas and requires less parking for workers.
Reduces Construction Waste
According to the U.S. Bureau of Labor Statistics, when comparing construction to manufacturing, 57 percent of activities in construction are wasteful and non-value adding. These are activities that are not compensated. However, 62 percent of manufacturing activities are value adding.
Replacing the wasteful elements of construction with manufacturing benefits through off-site construction can remove waste and increase value for projects. In fact, research shows that 77 percent of off-site construction users report a decrease in construction site waste.
Prefabrication at Work
These Stanford University projects illustrate the potential benefits of prefabrication.
Comstock Graduate Housing
With a need for four new student housing buildings before students arrived for fall quarter, Stanford University opted for a prefabricated concrete structural system over other building methods that would result in higher costs and take longer to complete.
The residence halls would provide 426 beds and over 180,000 square feet of living space. The structural system, which also formed the architectural skin and demising walls of the building, was constructed using vertically post-tensioned, precast concrete rocking wall panels, which were designed to rock at their base, with special energy dissipating rebar developed into the foundation and debonded up into the wall panel. The student housing complex was the first real, practical application of the precast concrete vertically post tensioned shear wall technology in California.
Prefabrication shaved six months off the construction schedule and moved 65,000 man days, defined as one day of work performed by one worker, off-site. Moving much of the work away from the active university campus sped up installation and increased safety, so the entire project ran more smoothly.
"We had four buildings up in three months. Typically, that would have taken the better part of six to nine months," said John Wong, Project Manager. "Once the third floor was up, we could start working on the first floor, whereas with traditional construction, we would have had to wait."
Escondido Village Graduate Residences
Stanford wanted to replace several of its current low-rise wood frame apartments with high quality mid- to high-rise buildings. The project, called the Escondido Village Graduate Residences, is a collection of four residence halls that range from 10, 8 and 6 stories, providing a total of 2,400 beds.
The site challenges were unique with students living nearby, limited parking and a confined space. Having experienced the success of the Comstock prefabrication, Stanford and the project team started the Escondido project with prefabrication in mind. This would reduce on-site labor and material deliveries, decrease traffic and congestion, limit campus disruptions, increase productivity and expedite the overall schedule.
Instead of a typical exterior cladding system that simply covers the structure in an aesthetically pleasing way, the structure was integrated with the exterior cladding, providing both the desired aesthetic and meeting the project's enhanced resiliency demands. Proposed prefabricated systems for the project went beyond precast to installing the glazing in the exterior precast panels in the factory setting to increase quality and further reduce construction activity on campus. Going with a total prefabricated system reduced risk, increased safety, minimized disruption on campus and shaved 11 months off the project schedule.
Whether you incorporate prefabrication into the structure and build on with other components for the full benefit of off-site construction, or you put prefabrication to work for part of a project, the results won't disappoint. What are you waiting for?