Sources of Changes in Design–Build Contracts for a Governmental Owner

Abstract

In recent years, many U.S. federal, state, and local governments have been authorized to use the design–build method of project delivery instead of the traditional design–bid–build method. Recent studies have not been definitive on the cost advantage of design–build for governmental owners. There are fewer change orders in design–build due to design errors because the designer (architect/engineer) and contractor are one entity, but there are other causes of change orders. Some literature suggests that changes requested by the owner of the facility are greater with the design–build method. This research examines the causes for construction-phase changes in 14 design–build and 20 design–bid–build projects. Total changes, expressed as number per contract, cost per contract, or percentage of original contract, were significantly lower in design–build. Fewer design errors in design–build accounted for this advantage. The number of owner-requested changes was significantly greater in design–build. The cost of owner-requested changes, averaged over all the projects, was significantly less for design–bid–build. The differences in changes due to differing site conditions were not significant. The concept that there are more owner-requested changes in design–build projects is supported by this research.