Impact of Design Errors on Variation Cost of Selected Building Project in Nigeria

Design error has been adjudged to be the main source of variation. However, empirical studies of the cost impact of design errors on variation are scarce. Therefore, this study aims to determine the impact of design errors on variation cost by investigating the prominent design errors that lead to variation, causes of variation in construction projects and impact of design errors on variation cost. The study was conducted on selected building projects in Nigeria. The mixed method (interview and case study) of research was adopted in the collection of necessary data. Interview was conducted among construction experts to obtain information on causes of variation on building projects. Thirty documents which include valuation breakdowns and variation/change orders documents were obtained by convenience sampling technique and used for the extraction of design errors leading to variations and their associated costs. The data were analyzed with frequencies, sums and percentages. The study found that poor working drawing and lack of coordination among documents are the major causes of variation. Omission of details on structural drawing and wrong description in specifications of architectural drawings among others are prominent design errors that lead to variation. The study indicates that design error account for up to 36% of variation cost. The study concludes that variation costs can be minimized to a large extent if government policies to ensure proper contract documentation are put in place and professionals are restricted from doing the works of others professionals.