Sources of changes in design: build contracts for a governmental owner

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