Construction Scheduling. Schedule Performance Measurement, Part 2. (For Owners).

When monitoring and responding to the Contractor’s schedule performance on the project, how do you know if the schedule update is even valid for use?

When we review a schedule progress update, we need to first determine if the schedule update is a valid update. By that, I mean is the logic still complete? Have there been any revisions with this update that result in the schedule not meeting the contract requirements or best practices? It doesn’t take much to render a schedule useless….

There are most likely logic revisions, changes to lag values, or possible changes to calendars or assignments. There are also deletions and additions of activities and/or Activity Relationships. Then there are changes to quantities or Resources which may impact Activity Durations or Resource Calendars.

For this post, we will address changes to the logic.

Personally, the first schedule “quality check” I make is for complete logic. The Primavera P6 schedule log provides a basic check. But I also use third party software that provides a more in-depth check for activities which may only have an SS relationship to their only successor activity. Sometimes, the check uncovers missing lag values or “reverse logic”. It may even uncover an SF relationship. All of these must be identified and addressed.

Often, when the Contractor is making schedule revisions to recover lost time for the update period, they make subtle changes to logic. As a Project Owner or CMa, we need to understand what was revised and why. If the relationship for an activity in the current or previous period Longest Path was changed from an FS relationship to an SS relationship, with or without a lag, to pull the scheduled Finish Date back, we need to understand that.

The same applies to the previous period or current update Near Critical Path(s).

If the contractor makes a logic revision for an activity which results in the only successor activity having an SS relationship, an open end is created. (There should have been an FS or FF relationship added to complete the logic). Otherwise, the finish of the activity does not drive anything in the schedule. This is an open end, (which does not show up on the Primavera P6 schedule log).

Any “open end” relationships make the schedule network logic incomplete. Sure, there are activities that once complete will not drive any other activity or work until the project is complete, if that is the case, they should be tied to Final Completion or whatever the last activity in the schedule is called. But more likely, the activity relationship was missed during development or when making revisions.

However, if this activity is supposed to drive other work, the relationships should model this. Not having complete logic for just one activity results in an erroneous schedule network. The activity could potentially be Critical or Near-Critical, but without the complete logic, there is nothing in the schedule to model the intended sequencing of the work for the affected network path. This means the Total Float values and scheduled dates for driven successor activities on this logic path are incorrect.

One of the basic checks and the first check I make is to verify the schedule network logic is complete. As an owner’s rep, we cannot know the detailed intent of the schedule sequencing, but we can identify open ends and any questionable logic we discover.

As  Planning and Schedule Professionals, we need to provide the Project Team with the “tools” they need to manage the project. The owner needs to know what the performance of the actual work in the field is, compared to the planned performance. Unless we have a valid schedule update to measure with, and against, and understand the impact of acceptable schedule revisions, we cannot provide an accurate measurement.

I’m sure many of you have comments or additional insight into this subject. Please share!

I’d love to hear what you think!

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Paul Epperson CCM, PMP, PSP, PMI-SP