Assessment of the Accuracy of Preliminary Cost Estimates for Commercial Projects in Abuja

Preliminary cost estimates form the basis of client financial commitment and investment decisions in the construction industry. Their accuracy is therefore critical in avoiding project abandonment, scope reduction, or financial distress. This study assesses the accuracy of preliminary cost estimates for commercial building projects in Abuja, using a sample of 35 projects with matched preliminary and final account costs completed between 2020 and 2024. A quantitative research design was adopted, with data collected from quantity surveying consultants and client organisations through structured questionnaires and project cost documentation review. Data were analysed using deviation analysis, descriptive statistics, and correlation. Findings show that preliminary estimates deviated from final accounts by more than 15% in 57% of cases, with most deviations being underestimates. The primary causes of estimation inaccuracy identified include inadequate scope definition, failure to account for inflation, exclusion of external works costs, and limited use of recent cost benchmark data. The study further finds that preliminary estimates prepared by qualified quantity surveyors demonstrate higher accuracy than those prepared by other consultants. Recommendations include the establishment of a national commercial building cost database updated quarterly, mandatory preliminary estimate validation checklists, and use of parametric cost modelling tools. This research addresses a significant knowledge gap on estimation accuracy for commercial development in Nigeria's capital city. Keywords: preliminary estimates, estimation accuracy, commercial projects, Abuja, cost management