Prefabrication is said to be the oldest new idea in construction. But it is no wonder that it continues to pervade as an ideal. The construction industry is fraught with litigation, inefficiency and waste. The design and construction of buildings are separate acts that are delineated contractually and legally identified and observed. Arguably, the divide between design and production has resulted in increased schedule delays and cost, and a diminished building quality and sustainability because the conception (architecture), optimization (engineering) and production (construction) are not integrated. In response to this inefficiency, prefabrication and modularization emerge and remerge as ideal methods of efficient production. McGraw-Hill Construction’s latest SmartMarket Report, “Prefabrication and Modularization: Increasing Productivity in the Construction Industry,” demonstrates how prefab architecture is yielding improved project schedules, decreased costs, and reductions in construction waste.
Although the ideology of prefabrication—harnessing the reduction of labor, decreasing schedules, and infusing greater control—is well understood, architects lack the structure for determining where and when fabrication is appropriate. Architects must understand the range of choices, opportunities and challenges associated with prefabrication to use it effectively. Prefabrication requires rethinking design throughout the building process. Specifically, architects must consider production thinking as a value-added measure to design, embracing notions of product theory and product design in the conception phase of development. The following are prefabrication production lessons for the design professional:
1. Decouple manufacture from assembly. Conceptually divide offsite and onsite activities, moving as many non-value-adding onsite operations to offsite control. Prefabrication takes the operations of fitting parts from the job site to the factory floor, especially time-consuming finish and detail work, leaving the assembly to larger subassemblies and fewer connections in the field.
2. Design for interchangeability. One manufacturing efficiency associated with the Industrial Revolution was the realization of the interchangeability of parts for a given product. This allowed random pieces to be selected and assembled to form many outputs. A movement toward more interchangeable parts and an increase in the production rate by favoring direct assembly onsite versus fitting parts on-site increases productivity.
3. Reduction in operations. This lesson has two principles. First, reduce the number of operations in onsite assembly resulting in potential reductions in assembly time, error, risk and cost. Second, reduce the number of parts in a subassembly and the number of subassemblies in an assembly. However, designers and construction professionals rely on conventions, which may be consistent from design to design but are not congruent with developments in manufacturing and production. When a part or subassembly is not functional or does not clearly benefit the integrated whole, it can potentially be integrated into another part or removed altogether.
4. Recognize scales of customization. Building fabrication may be standardized or custom. These terms, however, do not capture the complexity of the manufacturing and fabrication industry. The chief concerns in production thinking are costs, lead times and flexibility surrounding custom products. In general, as customization and flexibility increase, so do cost and lead times for product delivery. Mass customization suggests that digital automation has eclipsed economies of scale; however, this has not been realized in full. Instead, digital fabrication allows for a more predictable (just as useful) cost increase per degree of variation.
The terms made to stock (MTS), assembled to stock (ATS), made to order (MTO), and engineered to order (ETO) are used in manufacturing to define the extent to which a product is customized. This is generally considered proportional to the cost and lead time necessary for production.
5. Modularity. Although a fully integrated mass customization model is not entirely possible under current production methods, a few industrial design models can be transferred to architecture, including the following, illustrated through the example of a building product—exterior cladding:
Component-sharing modularity: same fundamental components with appearance variability within each discrete product (changing cladding options initially from project to project)
Cut-to-fit modularity: varying a product’s length, width or height by cutting it to size based on a fixed module (standardized cladding that can be increased or reduced in size in production)
Mix modularity: variation is achieved by mixing products (cladding in which multiple layers can be added or taken away in fabrication)
Bus modularity: a base structure that supports several attachments (a base frame that numerous cladding materials and systems can be attached to)
Sectional modularity: parts are different but share a common connection method (cladding panels may vary, but the connection to the frame is always the same)
Architectural production is clearly different from other types of production: It is unique every time, it is site specific and it uses a temporary labor force. Prefab architecture works to resolve these peculiarities. For building construction to progress and take advantage of the benefit of factory production, fitting must be expedited, taking construction to the factory and leaving assembly onsite. The maturation and market embrace of building information modeling (BIM) and integrated project delivery (IPD) suggest tools and organizational strategies can work concurrently with prefabrication to realize cost-efficient architecture.
Ryan E. Smith is the director of Integrated Technology in Architecture Center, University of Utah, College of Architecture + Planning.