Impacts of Change Orders on Cost and Schedule Performance and the Correlation with Project Size of DB Building Projects

Abstract

Few studies have been conducted to evaluate change orders in design-build (DB) projects, examining their impacts on cost and schedule performance, and their relationship with project size. This study analyzed cost, schedule, and change order data for 125 DB building projects to check whether the number of change orders for DB projects was higher than for design-bid-build (DBB) projects. All of the DB projects considered in this study had fixed their final guaranteed maximum price (GMP) before the design was 100% completed. One of the advantages of the DB delivery method is constructability, in which the designer can solicit feedback from construction personnel during the design phase; this can reduce the number of change orders. Results indicated that there were fewer change orders during DB building projects compared with DBB building projects. In addition, the percentage of projects that had cost overruns (21%) was significantly lower than that for projects that had cost underruns or were completed on budget (79%). In addition, the percentage of change orders in projects that had schedule overruns was not significantly higher than that in projects that had no schedule overruns; among other findings, the number of change orders increased as the size of the project increased (r=0.59).