Development of Value Based Decision Making Tool for the Selection of Offsite Manufacturing of Buildings Versus Traditional Method of Construction

Abstract

The traditional method of construction involves erecting buildings through assembling the bricks, blocks and scaffolders onsite. For many years, this has been the most common method of construction used in the construction industry. The major challenges associated with this traditional method are well documented. They include requiring time extensions; increased construction costs; high worksite accidents, and difficulties around the disposal of construction waste. Against this brief background, Off Site Manufacturing (OSM) appears to be a sound alternative method of construction. OSM is increasingly considered by researchers and some construction professionals due to its benefits, as evidenced from experiences in a variety of countries. However, despite OSM’s superiority over the traditional method of construction, in terms of time/cost savings, better quality control and enhanced safety performance, its uptake has been slow and rather limited. Reasons behind this slow uptake are varied and have been widely reported. A major reason appears to be the inability of OSM stakeholders (i.e. Clients, Developers, Manufacturers and Designers) to ascertain the short and long-terms Value that OSM will contribute, for a particular construction project, compared to that of the traditional construction method. To complicate matters further, project stakeholders, as one would expect, perceive the Value aspects of OSM differently. A critical literature review established the presence of a large number of Value aspects: 1) Product Value (e.g. usability, flexibility, etc.); 2) Process Value (e.g. profitability, customer satisfaction, etc.); and 3) Sustainability Value (e.g. life cycle costing, return on investment, waste generation, embodied energy, etc.). It is a certain combination of these Value aspects that may represent the source of motivation for stakeholders’ adoption of OSM. In a step towards addressing this challenge, this thesis presents a robust approach to assist decision-makers (i.e. project stakeholders) to make an informed decision about whether or not to adopt OSM for a particular construction project. In doing so, the thesis utilises the well-established Analytical Network Process (ANP) for determining Value aspects weightings, where each Value aspect is individually compared to other aspects, and the results are entered in a matrix for evaluation. To provide a user-friendly interface, Visual Basic for Applications (VBA) programming was employed. This programming language is the mechanism behind the functionality of the developed decision-making tool which generates relative weights and ranks, as well as benefit-to-cost ratios for both OSM and traditional method of construction for performing an objective comparison. In order to confirm the functionality of the developed decision making tool, validation tests were carried out using two hypothetical scenarios. This is to demonstrate that the tool conforms to the aims of the research. The validity criteria were based on the comparison of the manual calculations with the output of the decision making tool. The results from the hypothetical scenarios indicate that the tool functions are both correct and reliable.