Impact of change orders on construction productivity

Abstract

In construction projects it is virtually certain that there will be changes made during the course of the work, and that the owner (or design professional) and the contractor will seldom agree on the cost and schedule impact of the changes. This is particularly so on fast track construction, where design and construction are overlapped to accelerate the delivery of projects. Without a doubt, the most contentious area of impact of change orders is their effect on the productivity of the contractor's labour force. This paper presents the quantitative results of a comprehensive field investigation using 90 cases drawn from 57 different construction projects to identify the effects of change orders on productivity. The results indicate a significant direct correlation between the labour component of change orders and the loss of productivity, for both civil/architectural and electrical/mechanical works. These losses are exacerbated by the added presence of other major causes of productivity losses such as acceleration and inadequate scheduling and coordination. Regression models are developed for the direct estimation of productivity losses due to change orders, incurred both independently and in conjunction with other major causes of productivity loss. Key words: construction, productivity, change orders, contemplated changes, impact cost, quantitative models.