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By Duane Craig
September 18, 2017
While experience shows a healthy return of benefits to projects incorporating prefabrication, 86 per cent of construction firms surveyed by FMI and the BIM Forum said the prefab process is either not effective or needs improvement. Here’s why.
Prefab is a Mixed Bag
As a blanket term, prefab construction comes in several types. At the upper end are the complete buildings that manufacturers deliver to a site where crews “install” them on foundations or piers. Next come complete units that get hooked together to form a finished project or building. These units might also form one portion of a building like a bathroom. Then, there are trusses, laminated beams, and complete walls and ceilings.
A 2016 JB Knowledge Construction Technology Report cited prefab as occurring “most often with metal framing and drywall, MEP trades, concrete formwork, bathroom/unit pods and particularly on hospital projects or projects in rugged environments.” In a separate 2016 report by the World Economic Forum, “Shaping the Future of Construction: A Breakthrough in Mindset and Technology,” the authors painted a spotty picture of prefab adoption, pointing out surprising inconsistencies among countries and even within countries. For example, Scandinavia widely uses prefab for residential construction while prefab has made little headway for the same use in Germany.
Stakeholders See Different Benefits
While prefab is often touted as more affordable, quicker, and greener, each of those claims is debatable from a client’s perspective. That’s because there are too many factors involved and too many variables to say those benefits hold true all the time. For example, real estate developer Chad Ludeman points out that claims of affordability often don’t take into account the overhead imposed by the manufacturing facility, the manufacturer’s profit, site equipment needed to move large units, and customization fees. He also writes that while value engineering can save money on site built homes, over-engineering is often the case for manufactured homes. That can cancel claims of less waste.
But, from the perspective of a builder trying to deliver projects on time and on budget, there are credible reasons to consider prefab. The most obvious is quicker build times, as in the case of using laminated beams, trusses, prefab walls, and prefab ceilings. When it comes to And, in the case of modular residential prefab, some claim delivery of completed homes is 75% faster.
Builders can also benefit from better control over the schedule. Just consider hotel construction where a hundred identical bathrooms make up the install list. Dropping in prefab units with fixtures already in place, speeds up the process while improving both consistency and quality.
Other builder and developer advantages often claimed by prefab are:
Perception is Nearly Everything
As with anything new, prefab’s advantages must overpower entrenched attitudes and systems before growing to mainstream. The primary attitude that holds it back is the perception of it beingas a low- cost, inferior product that doesn’t offer much chance for customization. This perception has stuck with the industry for decades, even though advances have placed prefab on an even keel with other construction methods. A major roadblock here is zoning practices which tend to reinforce the negative perception by relegating prefab to marginal areas.
The rise of the custom client seeking very individualized design and finishes is tending to eliminate economy of scale advantages. These highly individualistic needs discourage using standard processes and products. Another reason for prefab’s lagging adoption comes from prefab applications that builders don’t have much experience with, like using prefab in high- rise projects. BesidesAnd, many contractors don’t want to lose control of the building process by involving partners who are not at the jobsite. This is especially true in light of the limited number and variety of prefabricators. Contractors might feel stuck with an underperforming manufacturer because alternates are limited.
Challenges for Vendors
To some degree, adopting factory processes for construction opens up new challenges on the supply side. The prefab market for construction is not mature, so prefab manufacturers face underutilization of their manufacturing space. BAnd, building codes may limit where certain types of prefab are allowed. Load sizes and limitations enforced by the transportation sector also constrain manufacturers. Transportation’s high costs for moving large units add uncertainty and price concerns for contractors, although, under the right circumstances some builders have used innovative methods to mitigate this.
For example, Skanska developed their own concept of “Flying Factories,” a term describing temporary factories located close to the jobsite. The factories use lean manufacturing principles and employ the local workforce. According to the World Economic Forum paper cited above, the solution reduced construction time by 65 per cent and labor costs by 50 per cent while improving on-site assembly productivity by 44 per cent.
Prefab units destined for multi-story buildings pose handling challenges. Not only do they require out-of-the-ordinary lifting equipment, but sections of walls or roofs can’t be finished until crews install the units. Financing prefab components also has nuances that can add a level of difficulty for including them on projects.
New technologies are poised to sweep aside the factors that are slowing prefab adoption. BIM is already providing the planning depth needed to make prefab integrate with on-site construction. A, and as 4D and 5D BIM developmature, the promise of prefab gets more tightly in sync with schedules and budgets.
As 3D printing matures, printing prefab components on site automatically increases their use. And, augmented reality is poised to help crews position and install prefab units more reliably and quickly. The tipping point to wide adoption will likely arrive when prefab wins the perception game once and for all.
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