The Epistemology of Cost Uncertainty in Construction Projects: Towards a Nigerian Theoretical Model

Cost uncertainty in construction projects is a fundamental challenge for the quantity surveying profession, yet the epistemological foundations of how cost uncertainty is understood, communicated, and managed in professional practice have not been theorised from within the Nigerian context. This study examines the epistemology of cost uncertainty in construction projects in Nigeria, developing an original theoretical model that integrates professional knowledge theory, decision science, and construction economics. A constructivist paradigm underpins a qualitative design employing 75 phenomenological interviews with senior quantity surveyors, project financiers, and clients across all six geopolitical zones and different project sectors. Interpretive phenomenological analysis was applied. Findings reveal that Nigerian quantity surveyors hold heterogeneous and often tacit epistemological frameworks for cost uncertainty, shaped by personal experience, client risk appetite, institutional norms, and geopolitical context. Cost uncertainty communication to clients is found to be systematically inadequate, with most practitioners defaulting to false cost certainty through single-point estimates despite awareness of substantial underlying uncertainty. The study develops the Nigerian Construction Cost Uncertainty Theory (NCCUT), which incorporates ontological (nature of uncertainty), epistemological (how it is known), and communicative (how it is expressed) dimensions. This theory provides a novel intellectual foundation for improving cost uncertainty management in professional practice and postgraduate education. Keywords: cost uncertainty, epistemology, theoretical model, Nigeria, quantity surveying