A Critical Examination of Cost Benchmarking Practices and Their Reliability in the Nigerian Construction Industry

Cost benchmarking is a fundamental professional activity underpinning the quality of quantity surveying services in construction, yet the reliability and methodological rigour of cost benchmarking practices in Nigeria have not been systematically investigated at a doctoral level. This study critically examines cost benchmarking practices and their reliability in the Nigerian construction industry, investigating how cost benchmarks are constructed, maintained, disseminated, and applied across the profession. A critical realist paradigm underpins a multi-method design employing document analysis of 50 professional cost guides, statistical reliability analysis of cost benchmark datasets from 20 firms, and 55 semi-structured interviews with senior practitioners. Structural content analysis and reliability testing using intraclass correlation coefficients were applied. Findings reveal that most cost benchmarks used in Nigerian quantity surveying practice are characterised by inconsistent data collection protocols, non-representative sampling, inadequate zone disaggregation, and update frequencies insufficient to reflect inflationary conditions. The coefficient of variation in cost per square metre benchmarks for comparable building types across Nigerian sources exceeds 45%, significantly exceeding acceptable reliability thresholds. The study develops a Cost Benchmark Reliability Assessment Tool (CBRAT) providing a structured methodology for evaluating and improving the quality of Nigerian construction cost benchmarks. This research makes an original methodological and critical contribution to cost information science in the Nigerian built environment profession. Keywords: cost benchmarking, reliability, quantity surveying, Nigeria, cost information