Do you ever look at a schedule and wonder why a series of related activities will have different Total Float values? Perhaps the activities on the Critical (Longest) Path?
It just makes sense that the activities in the same work path would have the same Total Float value.
However, when your contractor develops the project baseline schedule, they develop the various Activity Calendars for the project. There may be a 7-Day Work Week Calendar for Milestone Activities, Level of Effort Activities, and fabrication or delivery activities. There may be a 5-Day Work Week with Holidays Calendar for work planned for normal work days but not on holidays. There may be a weather calendar with specific days set as non-work days to allow for the anticipated normal weather impact days.
Each calendar will have a different action on the Total Float value because each calendar only allows the work to be scheduled on the work days for that specific calendar. This, in turn, determines the Total Float value.
This is why the Milestone Activities on the Critical Path may have a value of -7 days and the activities on the 5-Day Work Week Calendar may have a value of -5 days. The 5-Day Work Week Calendar doesn’t take the weekend non-work days into account with the calculation. The total Float value for the activities assigned to a weather calendar would also be different.
This is also why a set period impact to the schedule, such as 30-day delay in receiving direction to start work on a work package could have a larger delay to the contract completion. A 30 Calendar Day impact can push the work over non-work periods such as holidays and weather resulting in a 35 Calendar Day impact to the contract Completion Date. This must be accounted for in the Time Impact Analysis so the party not responsible for the delay is not forced to absorb this variance.
The bottom line is: Don’t let Total Float values determine what is critical, let the schedule software do that by using the Critical Path definition of Critical = Longest Path. Using the Total Float values is valid for many things, but determining your Critical Path isn’t one of them. If you have more than one calendar for the activities, there will be differences in the Total Float values.
I know many of you can offer additional comments and recommendations. I welcome your comments and input. My goal, as always, is to help our industry and help the projects we support….
I’d love to hear what you think!
Please visit https://conschmanservices.com to learn more about Construction and Schedule Management Services, LLC
Please visit my LinkedIn account to learn more about me.
Please visit my “The Blue Book” ProView.
Paul Epperson CCM, PMP, PSP, PMI-SP