Mechanisms of time and cost effects in construction projects

Abstract

The study investigates how events arising during the preparation and delivery of construction projects lead to time and cost effects, and what evidence distinguishes a demonstrated causal relationship from a merely possible one. The source collection comprised 87 expert reports, preliminarily grouped into 80 independent matters and containing 950,929 words. Ten maximally varied cases, represented by 14 reports and 299,624 words, were selected for in-depth analysis. Thirty-five causal sequences were reconstructed using five elements: initiating event, participant response, change in the actual course of the works, and separate assessments of schedule and cost effects. Design documentation and design issues initiated 28.6% of the causal sequences, while access, decisions and approvals initiated 22.9%. The two most common ways in which effects arose were changed, additional or repeated work (34.3%) and the absence of conditions necessary to proceed (25.7%). Among the 29 sequences in which schedule effects were assessed, 15 effects were demonstrated and six were considered probable. In all eight cases classified as possible, not established, absent or not independently attributable, the effect on the critical path was missing or explicitly excluded. Supplementary expert reports further showed that new evidence may revise the magnitude of an effect without changing how it arose, or may require an earlier attribution of delay to be withdrawn. The findings support assessing construction disputes through reconstructed causal sequences instead of directly associating an event with delay or cost growth.