Cost Reduction Through Prefabrication: A Design Approach

Abstract

The Grow Home is a 93-square-meter rowhouse, 4.3 meters wide, developed by the Affordable Homes Program at McGill University in response to the affordable housing challenge. The kitchen, bathroom, and living room are located on the ground floor, and an unpartitioned second floor is proposed in an effort to reduce costs and enable the owners to complete the unit at their own discretion. This paper examines how the Grow Home can be adapted to an industrialized method of production, using prefabricated panel systems, and determines the implications such construction would have in terms of quality, economy, and technical performance. The research includes an adaptation to the unit’s design and a cost estimate comparing prefabricated systems with conventional construction methods.

A framework for the industrialization of the Grow Home was developed by adapting the units design to provide sufficient flexibility for the builder and economies of scale for the manufacturer. Architectural, modular, and technical design criteria were established based on feedback from manufacturers, builders, and occupants of existing Grow Home projects. A wide range of options for the dwelling’s layout was generated using a small number of simple, standard components. Nine panel configurations were proposed in all, six for the front and back elevations and three for the side walls of the end units. The use of small, standard interior partitions provided various configurations for entrances and bathrooms, while enabling on-site changes to be made fairly easily in response to a client’s request.

The potential for prefabricated systems to reduce construction costs was addressed by examining the costs of several prefabricated components, including exterior walls, floors, partitions and dividing walls. The analysis demonstrated that prefabricated panel systems can, for the most part, provide a competitive alternative to conventional construction. The magnitude of the savings, however, can vary significantly depending on the type of panel system, the degree of préfabrication, and the component in question. When the scope of prefabricated components was extended to include floors and partitions, savings up to 6% were found to be possible. For the construction of 30 or more units, this represents savings of up to $95,000 ($3,150 per unit).

Additional information

Notes on contributors

Avi Friedman

Avi Friedman is an Associate Professor and Director of the Affordable Homes Program at the McGill University School of Architecture in Montreal, Quebeq, Canada.

Vince Cammalleri

During the writing of this article, Vince Cammalleri was a research associate to Professor Friedman.