Reliability of Preliminary Cost Estimates of Educational Building Projects in a Developing Economy

Abstract

This study focused on the reliability of preliminary cost estimates of educational building projects in Nigeria with a view to providing more reliable cost estimates and reducing the number of abandoned educational building projects caused by faulty preliminary estimates. Using a case study approach, a total of 33 completed educational building projects were assessed and 31 construction professionals (Quantity Surveyors and Architects) formed the secondary population of the study. Data were analyzed using frequency, percentage, relative importance index, paired sample t-test, effect size and variance ratio. The study revealed that approximate quantities is the most commonly used method for preparing preliminary cost estimate of educational building projects while there exist a significant difference between the preliminary cost estimate and final cost of construction of educational building projects. Despite this difference, the preliminary cost estimate is still reliable as a considerable level of accuracy was discovered. The major factors affecting the reliability of preliminary cost estimate are variation due to changes in design and specification, experience of the estimator and site condition. The study therefore recommends that care should be taken when carrying out preliminary estimate and estimating should be done by professional with experience in such area. During construction, all works should be carried out according to specification in order to avoid deviation from initial plan and estimate.

Keywords: Nigeria, preliminary cost estimates, final construction cost, educational buildings