A decision evaluation model to choose between manufacturing off-site or on-site methods for construction of house building projects

Despite the wealth of knowledge and information on off-site manufacturing systems, current decision making models do not adequately provide a clear cut choice between using offsite manufacture of building elements and onsite in-situ construction, especially at the pre-construction stage. This paper describes the development of a Decision Evaluation Model (DEM) that provides this opportunity particularly for house building projects. The primary objective of the model is to improve the quality of information on which the decision is based. Having carried out an extensive literature review, primary research data and information was collected from 30 structured interviews, questionnaires completed by 30 selected respondents, and 30 case studies made up of 15 manufacturing 'offsite' projects and 15 projects using 'onsite' construction methods. A robust set of factors have been identified, measured and ranked according to their significance in the decision. Using these factors, a methodology has been developed to measure and evaluate the characteristics of a project, which forms the core of the DEM. The developed model enables decision makers to clearly establish whether to use offsite or onsite construction as a construction strategy. The DEM model provides the opportunity to assist the construction practitioners and clients in making decisions based on adequate data and predictable outcomes against any given project within its environment.