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(PS-2292) When Measuring Delays, Negative Float Doesn't Matter!

Primary Author: Mark F. Nagata, PSP
Co-Author(s): Bryan Van Lenten

Audience Focus: Intermediate
Application Type: Practice
Venue: 2016 AACE International Annual Meeting, Toronto, ON, Canada

Abstract: There's a misconception that the existence of activities showing negative float in a construction schedule imparts added significance to those activities, requiring special consideration when measuring delays. This is unfounded and ignores the basic principles of CPM scheduling and schedule analysis, such as the principle stating that only delays to the critical path, which is the longest path in the schedule network, will result in project delay. This paper will logically and methodically explain why, when measuring delay on a construction project, negative float does not matter. Additionally, this paper will explain what float is, how float is calculated, why negative float exists, how multiple calendars and constraints affect the calculation of float, why Total Float values alone should not be used to determine the project’s critical path, and why the critical path should be defined as the longest path in the network.