The development of decision evaluation model (DEM) to determine between manufacturing off-site or on-site methods for the construction of house building projects

It is a common statement that construction decisions are described as difficult, because typically they involved high uncertainty, complexity, risk consequences, alternative construction methods and products, and numerous stakeholders with different interest. This research focuses on choosing a construction strategy between off-site manufacturing systems and on-site methods for a project. This requires an optimum decision strategy which involves careful understanding, measurement and evaluation of a number of factors that can have the most influence on alternate decision outcomes. The aim of this paper is to describe the development of a Decision Evaluation Model (DEM) that provides a clear cut choice between using offsite manufacture and onsite construction methods at the pre-construction stage for house building projects. Having carried out an extensive literature review, primary research data and information was collected using 30 semi-structured interviews, questionnaires completed by 30 carefully selected respondents, and 30 case studies made up of 15 projects that used ‘off-site’ manufacturing and 15 other projects using ‘onsite’ construction methods. A robust set of factors have been identified, measured and ranked according to their significance on 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 and further case studies were used to test the validity of the developed model. The primary objective of the model is to improve the quality of information on which the decision is based and to enable decision makers to clearly establish whether to use ‘offsite’ or ‘onsite’ as a construction strategy.