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In 2012/2013, CERC received a Skanska Innovation Grant to study the potential for modular prefabricated construction for mid- to high-rise residential buildings in Seattle.
The current practices in the construction industry are labor-intensive and surrounded by significant risks associated with market, site and weather conditions. In addition, the construction industry has been criticized for lower productivity relative to other US industries in the last forty years. Many seek efficient improvements with respect to time, cost and quality. Modular construction moves the construction site to manufacturing facilities for a major part of the building and, in this way, improves its predictability, increases productivity, and reduces the risks inherent in construction. Modular buildings also generate great cost savings opportunities as a result of compressed construction schedules.
The key objective of this report is to provide a review of the potential for modular prefabricated construction for mid- to high-rise residential buildings in Seattle. To achieve this objective, we identified 9 major constraints and 3 main opportunities in implementing this type of construction. The constraints include market demand, transportation, logistics, costs, codes, permitting and inspection, labor and unions, architectural design and delivery, and regional manufacturing. Structural design is another constraint that is not covered in the present report, but should be carefully considered particularly in seismic regions such as Seattle. Furthermore, the major opportunities of this type of construction include schedule, cost, and quality. We also studied several case-studies of modular mid- to high-rise buildings from a variety of regions including the US, Europe and Australia to understand how this construction method has been utlized globally. Finally, we present the design and analysis of three student studio teams in an Integrated AEC studio which was conducted as part of Skanska’s innovation grant. The student team proposals are for mid-rise residential modular buildings in a hypothetic site in Seattle.
We conclude that there exists a great potential for modular construction in the delivery of high-rise residential buildings. There is a strong demand for multi-family housing in the Tri-county region, however, there appears to be significant oversupply of multi-family units coming onto the market in the medium term, which should be considered prior to any release of units onto the market. Therefore, it is suggested that further investigation is conducted to understand the fluid nature of the housing demand and supply in the region. When such a project is undertaken, the size and weight of the modules to be used in a modular building should be carefully considered with respect to transportation, logistics. Typical module sizes are 11 feet high, 12 to 16 feet wide, and 55 to 65 feet long. A maximum 200-mile distance from the site location is probably the most cost-efficient option with respect to transportation of the modules and trucks are usually the preferred transportation system. These transportation costs are minimal as compared to the potential for reduced site construction and financing costs as a result of smaller crew sizes and shorter construction schedules