Architecture/Construction
SMITH
—From the Foreword by James Timberlake, FAIA
THE DEFINITIVE REFERENCE ON PREFAB ARCHITECTURE FOR ARCHITECTS AND CONSTRUCTION PROFESSIONALS
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ritten for architects and related design and construction professionals, Prefab Architecture is a guide to off-site construction, presenting the opportunities and challenges associated with designing and building with components, panels, and modules. It presents the drawbacks of building in situ (on-site) and demonstrates why prefabrication is the smarter choice for better integration of products and processes, more efficient delivery, and realizing more value in project life cycles. In addition, Prefab Architecture provides: ■
A selected history of prefabrication from the Industrial Revolution to current computer numerical control, and a theory of production from integrated processes to lean manufacturing
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Coverage on the tradeoffs of off-site fabrication including scope, schedule, and cost with the associated principles of labor, risk, and quality
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Up-to-date products featuring examples of prefabricated structure, enclosure, service, and interior building systems
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Documentation on the constraints and execution of manufacturing, factory production, transportation, and assembly
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Dozens of recent examples of prefab projects by contemporary architects and fabricators including KieranTimberlake, SHoP Architects, Office dA, Michelle Kaufmann, and many others
In Prefab Architecture, the fresh approaches toward creating buildings that accurately convey mature and expanded green building methodologies make this book an important voice for adopting change in a construction industry entrenched in traditions of the past.
A GUIDE TO MODULAR DESIGN AND CONSTRUCTION
RYAN E. SMITH is Director of the Integrated Technology in Architecture Center (I TAC), an interdisciplinary research consortium at the University of Utah College of Architecture + Planning in Salt Lake City, Utah (www.itac.utah.edu). Smith’s research and teaching focuses on promoting integration that leads to sustainable and lean design and construction practice.
PREFAB ARCHITECTURE
“Prefab Architecture . . . is beyond theory, and beyond most of what we think we know about pods, containers, mods, and joints. This book is more than ‘Prefabrication 101.’ It is the Joy of Cooking writ large for the architecture and construction industries.”
PREFAB ARCHITECTURE A GUIDE TO MODULAR DESIGN AND CONSTRUCTION
RYAN E. SMITH FOREWORD BY JAMES TIMBERLAKE, FAIA
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4.1.2 Schedule Arguably the greatest benefit to productivity of offsite fabrication is a reduction in onsite construction duration.6 The savings in time on prefabricated building projects come in the ability to simultaneously construct in the factory while site work is being completed. Rarely are precast foundations used, therefore site work and foundation can be constructed onsite concurrently with prefabrication work of structure, enclosure, services, and interiors being produced in a factory. Whereas traditional onsite construction is a linear process by which subcontractors wait until the preceding trade has completed their work, in a factory, teams may work concurrently allowing entire sections of a building to be constructed by more than one trade. In addition, multiple fabricators can be manufacturing subassemblies that are brought together and assembled onsite. Time savings may also come by way of employing lean production techniques. Reductions in schedule may not initially come to fruition in one-off or highly customized production runs, but can occur through an increase in repetition. In order to have concurrent factory and site work occurring, delivery may need to become front-loaded, meaning that the majority of planning occurs before construction through an integrated process. Decisions regarding prefabrication are made early so that schedule savings may be realized from the start of construction. Prefabrication offers more predictability in finish dates. This is due to the ability to procure materials and processes more quickly and the fact that prefab occurs in a controlled environment where weather does not have an effect on the labor force. Interest on financing is compounded at a higher rate and therefore more costly on longer construction dura-
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tions. Public buildings may have more leeway on schedule, but for daily income-generating companies, the ability to open according to schedule determines whether they are able to go into business at all. A business opening at a certain time of year, needing to open for a retail season; schools that need to open for students in a new semester; and hospitals that must open beds for populations that may be underrepresented with health care, are all buildings that are restricted by schedule. For example, in the author’s experience, while working for an international A/E firm designing microchip plants in East Asia, each day that was over schedule in construction was a loss in hundreds of thousands of dollars in revenue for the technology company. In addition, for operating existing buildings, the less retrofit and remodel disruption the better. Adrian Robinson at Buro Happold Engineers shares his experience with schedule reductions when using prefabricated steel modules on a hotel project in the United Kingdom. The Travelodge Hotel engineered by Buro Happold broke ground the same time as a hotel of similar size across the street, near Heathrow Airport. The Travelodge Hotel was entirely dried in while the hotel across the street had not finished steel framing. Amy Marks at Kullman, fabricator for a few of KieranTimberlake projects, states that on average they are seeing a 50 percent time savings reported from their contractors for offsite methods over onsite in the steel and concrete commercial building sector. This is especially true in her opinion in projects that employ larger modules and panels in greater quantities. The economies of scale for cost are not as much a factor as the economies of schedule in prefabrication for larger commercial buildings. In residential construction, Michelle Kaufmann reports that in her experience with prefabrication, comparing the first Glidehouse she built onsite using the stick
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ONSITE CONSTRUCTION
4.1 PRINCIPLES
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SD DD CD Permits Bidding Site Work Construction
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Figure 4.4 This Gantt chart compares the project duration from conception to completion of two similar houses, one built onsite and the other offsite. Prefabrication saves over 50 percent in total project duration as a result of modularizing the units. The greatest savings in schedule can be seen in the concurrency of onsite and offsite work in the prefab project as well as overall construction time. Michelle Kaufmann designed both houses.
Start-Up Substructure Superstructure Space Services Finishes Commission
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Figure 4.5 Comparing a small construction project using the methods of onsite versus offsite demonstrates a savings of 50 to 70 percent in project duration by Kullman Building Systems.
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framed method to the second Glidehouse, prefabricated as a module offsite, the duration of the project was nearly half for the modular prefab. This can be attributed to the concurrency of the onsite and offsite construction activities as well as the direct construction of the house proper not including the foundation or utilities. Weather can also affect the duration of construction on a job site. In a site-cast concrete multi-family housing project in Utah, the cold weather of the winter delayed the project three months due to unexpected snowstorms and below average temperatures that required crews to install warming blankets during curing. This labor-intensive process cost the project leasing revenues for the months that were over schedule. In a recent housing project, Irontown Homes, a modular builder in Spanish Fork, Utah, was able to fabricate building modules one month ahead of schedule. Seeing that the duration of the project could be beat, the project team decided to ship the modules and set during the middle of winter. Onsite, a blizzard ensued, taking the setting schedule an additional day than was originally planned, whereas building an onsite house in the same weather conditions would not have been feasible. As Tedd Benson of Bensonwood Homes says, “In the factory, the sun always shines.” 7
4.1.3 Labor Safety of workers is increased by virtue of the conditioned, dry interior environment of the factory. Onsite construction not only requires workers to potentially be exposed to harsh conditions of weather and precarious positions near roads, hazardous protrusions, and the like, but also requires workers to travel long distances, even across state lines, in some cases, in order to complete a project. Projects outside of
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metropolises require onsite construction workers to stay in temporary accommodations and travel home on the weekends. Prefabrication offers an opportunity for shorter commutes. This reduces cost and risk of workers traveling to and from the jobsite on highways when they are fatigued after working long hours. Systematizing the construction process in a factory presents opportunities for workers to establish a regular schedule, not having to do early mornings in hot regions, for example, in order to beat the late afternoon sun. In many cases, this does not allow for a full day’s work, while a factory environment provides full eight-hour days, or in fast-track projects, back-to-back alternating of shifts, thus further reducing total construction duration. Factory work is regulated with respect to levels of noise, dust, air quality, material waste, and recycling.8 The International Labor Organization estimates that there are at least 60,000 fatal accidents on construction sites across the globe annually. This equates to one accident every 10 minutes and 17 percent of all fatal workplace accidents.9 In the United States, fatal and nonfatal injuries due to construction double that of the manufacturing industry.10 In fact, the only category in which manufacturing has a higher number of injuries is in equipment injury, but only by a total of 10 individuals. By moving to prefabrication, the construction industry and its workers can experience a much safer environment by a factor of 2. Lingard and Francis found that employees in site-based roles reported higher levels of conflict at home and exhaustion than employees who worked in regional or head offices. This should be no surprise to anyone connected to the construction industry, and it must be acknowledged that long weekends and long hours contribute to poor emotional health. This study also points to the higher rate of turnover of employees in construction
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than that of the military, technology, and management sectors.11 Prefabrication certainly cannot cure the evils of construction, but by bringing the work into the factory, prefabrication has the opportunity to invest in programs that control employee satisfaction in the workplace. Nutt-Powell comments that prefabrication allows for manufacturers to employ unskilled workers. In onsite construction, skilled work is required because of the range of tasks necessary. A knowledge of how individual pieces of a project are coming together as a whole requires skills beyond many entry-level positions in the construction trades. If a worker makes a mistake onsite, it is detrimental to the progress of the project. The reality of most construction sites is that unskilled workers are commonly unsupervised. In the factory, unskilled work is more easily managed. The laws of supply and demand dictate that some laborers earn more than others. Therefore, lay construction workers naturally select jobs that are higher paying, and not necessarily what they are most qualified or skilled to perform. Conversely in prefabrication, factory workers can be paid the same for different tasks, rewarding wages based on performance. This encourages laborers to gravitate toward jobs that they enjoy. Nutt-Powell argues that this potentially increases skill levels in construction tasks.12 Society places value upon certain kinds of work and rewards individuals accordingly. Although the factory worker we have been discussing in this chapter may have an opportunity to become quite skilled in a particular task, the work is still considered unskilled, meaning that the market does not compensate it well. In addition, these jobs are monotonous, leaving those who perform them in the same task over and over without variation or a challenge. In order
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for prefabrication to be ethically accepted among the building industry, it must shed the stigma of human rights infringements with which it is associated. With computer technology and an increase in the complexity of factory production techniques in the later part of the twentieth and early-twenty-first century, as well as the employment of single-piece workflow and lean project techniques, it is likely that the prefabrication architecture laborer is much more skilled than any mass-production laborer in previous generations, moving to more intellectual, computer, or even management tasks. The macroeconomic context in which a construction project finds itself has much impact on the feasibility of using offsite production methods. In residential construction, when work is plentiful and the economy is strong, prefabrication is able to compete with onsite methods, as a surplus of work shifts operations offsite. In times of economic depression, builders will opt for methods that pay unskilled onsite workers, despite the resultant longer durations. This is truer in the western state markets like Salt Lake City. For example, panelization of frame walls gained much strength during the 1990s and early 2000s; however, according to Burton Lumber, a prefabricator of panels and trusses, the recent recession has virtually removed their panelized market share. In discussing the issue with their customers, builders, and architects, Burton Lumber found onsite-framed construction to be cheaper because bids are coming in a record low from immigrant day laborers. Once the economy rebounds, however, the company would like to be more poised than ever to handle offsite production methods in greater variety and capacity. This is a challenge prefab will always have to compete with, until the market share becomes the majority, making it more expensive in general to build onsite.
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Conversely, Kullman Building Corp. has seen an increase in market share of steel and concrete construction for commercial buildings since the economic downturn. Architects and contractors are trying to find new ways to build and questioning the traditions that are associated with the recent real estate recession. As more architects move to using BIM in their design and delivery process, Kullman
PRINCIPLES
is able to keep costs, schedule, and predictability closer in tact. On higher capital investment projects in the commercial sector, owners and contractors want to know with the greatest accuracy cost and schedule. Going to greater degrees of prefabrication in the factory and finishing elements to above 90 percent allows for little onsite uncertainty to creep in.
PREFAB IMPACTS ON LABOR PRODUCTIVITY Productivity is a measure of efficiency in labor. With offsite fabrication, technical changes including machinery in the factory, evolutions in material science, and finally digital revolutions in BIM and CNC have positively impacted the productivity of labor in construction. Goodrum and colleagues published a study in which these improvements and productiveness were evaluated as a result of the functions of prefabrication. Advances in machinery, physical tools for manufacturing, and prefabrication technology, or in short, equipment technology, have impacted labor productivity through the following means: • Amplified human energy to increase output • Increased levels of control, precision, accuracy, and quality • Added variability to production manipulation • Increased information processing via CNC tools • Improved ergonomics for reduced fatigue and increased safety Material advances have increased productivity through: • Reduction in the mass of materials • Increase in strength of materials • Curing and cooling time for materials • Installation flexibility in different weather conditions • Offsite customization of materials Based on 100 construction-related tasks, the researchers found that labor productivity for the same activity increased by 30 percent where lighter materials were used. In addition, labor productivity also improved when construction activities were performed using materials that were easier to install or were prefabricated. Productivity cannot be a factor of material and production technology alone; however, the report shows a significant increase in productivity in projects that incorporate not only material advances in prefabrication but equipment and information technologies as well.13
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