Effects of Delivery Systems on Change Order Size and Frequency in Mechanical Construction

TLDR

Change orders are a major source of cost growth and field‑generated, unforeseen orders disrupt productivity on construction projects. The study aims to examine how design‑build delivery methods affect the frequency and magnitude of change orders in mechanical construction. The authors analyzed 598 change orders from 120 projects by the same contractor, comparing design‑build and design‑bid‑build delivery methods to assess their impact on change‑order frequency and magnitude. Results revealed that design‑build projects experienced an 87% reduction in the average number of unforeseen change orders and an 86% smaller average size, demonstrating the effectiveness of design‑build business practices.

Abstract

Change orders represent one of the largest sources of cost growth on building construction projects. Field generated, or "unforeseen" change orders can also be highly disruptive to field productivity. Design-build delivery methods can potentially help minimize change orders on construction projects. This study was performed to closely examine the effects of delivery methods on the frequency and magnitude of change orders in mechanical construction, and how design-build business practices can be used to minimize the frequency of field generated chance orders. In a study of 598 change orders occurring on 120 construction projects performed by the same contractor, the total number of change orders was found to be close to the same on design-build and design-bid-build projects, however an 87% decrease in the average number of unforeseen change orders was observed on design-build projects versus design-bid-build projects. In addition, the average size of unforeseen change orders was 86% smaller on design-build projects. A detailed and qualified presentation of the research methodology and resulting data is provided. Key attributes and business practices leading to the results are discussed and practical applications of this research for owners and contractors are provided.