Management of material waste and cost overrun in the Nigerian construction industry

While wastage of materials has become a serious problem requiring urgent attention in the Nigerian Construction Industry, cost overrun is a problem, which affects 90 percent of the completed projects in the world; the argument on how to reduce/eliminate cost overrun has been on-going for the past 70 years; as the on-site wastage of materials leads to increases in the final project cost. Studies from different parts of the world have shown that construction-material waste represents a relatively large percentage of the production costs. Consequently, as a result of low levels of awareness, the Nigerian construction industry pays little attention to the effects of generated material waste on cost overruns. Thus, this research aimed to investigate the relationship between material waste and cost overrun in the Nigerian construction industry. A comprehensive review of the related literature revealed that all material waste causes are related to cost overrun causes at both pre-contract and post-contract stages of a project; but not vice versa. The mixed method (quantitative and qualitative) approach that is rooted in the positivist paradigm was adopted for this study. Abuja, the federal capital territory of Nigeria was the selected geographical scope of this research, out of which thirty-one (31) construction projects were purposeful selected (projects to the value of 100 million Rand/1.6 billion Naira and above).The research instrument was an interview guide used in conjunction with a tick box. Other sources of data included field investigation (measurement of onsite material waste) and the collection of archival records from bills of quantities, project records, and specifications. Analyses of the findings lead to the conclusion that a relationship exists between material waste and cost overrun; at the pre-contract and at the post-contract stages of a project. The implication is that an increase in material wastage on-site leads to a corresponding increase in the amount of cost overrun, regardless of the percentage allowance for material waste in the process of bill preparation. The study also concluded that the average percentage contribution of material waste to project-cost overruns is four (4) percent. Material-waste sources, causes, and control measures were found to have significant effects (very high, high, medium, low, and very low), in causing or minimising cost overruns at both pre-contract and post-contract stages of projects. The research has developed a conceptual model for the management of material waste and cost overruns in the construction industry based on the results and informed by the theoretical framework. The research has also developed a mathematical model for quantifying the amount of material waste to be generated by a project; as well as a mathematical equation for the effective management of material waste and cost overrun for projects. The study has achieved its aim of establishing an understanding of the issues leading to the relationship between material waste and cost overruns, as well as their management in the Nigerian construction industry. The study recommends that the management of material waste and cost overrun should be revised, based on the findings of this research and included as part of the procurement process. The mathematical models for quantification of onsite material waste, and the mathematical equation for managing material waste and cost overruns developed in the study, could be usefully adopted to improve management of material waste and cost overrun in the Nigerian construction industry