The decision to use off-site manufacturing systems for house-building projects in the UK

The decision to use Off-Site Manufacturing (OSM) as a construction strategy in the house building industry is often made using ‘gut-feel' or poor information and at the wrong time and for the wrong reasons. Research has shown that the correct use of OSM in house building has the potential to address some of the key challenges facing the UK house building industry, such as the increase in supply of new homes, skills shortage gap, the need to reduce CO2 emissions and environmental impacts, reduce overall project duration, minimise overall project costs, and reduce defects in new housing. However, with poor decision making surrounding the use of OSM, this potential remains untapped. At the strategic level, construction decisions that require executive data and the use of expert systems and decision support systems for evaluation are often unstructured or semi-structured. Such support systems are currently not available with respect to the use of OSM as a construction strategy. There is evidence to suggest that this results in poor understanding of the decision making process and the issues surrounding the process. This thesis therefore aims to develop a Decision Support Model (DSM) that can be used in practice to guide the choice between OSM and Traditional On-Site (TOS) production as a construction strategy in house building projects in the UK. The study was based on two main sources of data collection: firstly, an in-depth literature review of existing knowledge associated with the use of OSM and decision making process in the construction industry with particular reference to house building; and secondly, primary data collection using semi-structured interviews, questionnaires with key construction practitioners, and case based precedence review of numerous housing projects that have used both OSM and TOS in the UK. The findings from both sources were analysed and used to develop the DSM. The research initially established a robust set of sixteen key decision factors; then produced a Severity Indices Matrix (SIM); and finally developed a methodology for arriving at a decision outcome. The DSM provides a reliable system that transforms an unstructured situation into a structured decision making process and improves the quality of information required to arrive at an outcome within its project environment. The research has identified the most suitable time in the project life cycle that the decision needs to be taken to achieve an optimum outcome. It has also established that the client, the architect and the main contractor must all be involved in the decision making process.