Abstract
Design error has been adjudged to be the main source of variation. However, e mp irica l 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 (intervie
w and case study) of research was adopted in the collection of necessary data. Interview was
conducted among construction experts to obtain informat ion 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 extract ion of design errors
leading to variat ions and their associated costs. The data were analy zed with frequencies, sums
and percentages. The study found that poor working drawing and lack of coordination a mong
documents are the major causes of variation. Omission of details on structural dra wing and wrong
description in specifications of a rchitectural drawings a mong others are pro minent 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 b e minimized to a large e xtent if govern ment
polic ies to ensure proper contract documentation are put in place and professionals are
restricted fro m doing the works of others
professionals.