Construction Scheduling. Checking the CPM Schedule for Complete Logic, Verifying the Use of Calendars, and Identifying Constraints.

When someone hands you the schedule update Gantt Chart pdf, how do you know that the plan is valid? How can you do a quick validation of the schedule for basic requirements?

First and foremost, a pdf of the schedule is nice for meetings, but someone from the owner’s and the contractor’s project teams needs to verify the schedule quality & validity. The contractor usually has an in-house scheduler, so this is part of their work during the development, update, and revision processes. What about contractors using a third-party planning and schedule professional? How do you validate our work? What about the owner and their construction management agency? How do they validate the schedule as presented by the contractor?

The owner and CMa will require the schedule in native format. That will allow their planning and schedule professionals to use the schedule program and verify schedule settings and structure. This is a must. I still see owners who simply look at the pdf and hope the schedule slippage will stop, one day….

Simply reviewing the schedule log generated by Primavera P6 will let you see the open relationships, out-of-sequence relationships, schedule settings, constraints, and other information. This report includes the most basic information you need.  You should receive and review this report!

If you only have one activity missing a predecessor and one missing a successor, you are OK. This doesn’t mean all the logic in the schedule is correct, that is a very subjective review. It just means you don’t have any open ends reported. You can still have activities with only start-to-start successor relationships, which is basically the same as having no successor relationship. But, you need third party software or the ability to use the program filter, sort and report features to ferret these out.

The out-of-sequence activities listed on this report simply tell you that the successor to these activities most likely started prior to the finish of the activity listed. There are other reasons the activity may be listed, but this is the most likely reason. Why does this matter? Because the logic continues to drive successor dates and correcting the logic ties to model the as-built progress allows the remaining work to model correctly. It also provides you with an as-built schedule, one day….. Require the contractor make corrections to remove all out-of-sequence activities from the schedule log. It’s not hard for them to do.

The schedule settings are typically listed in the schedule specifications. You can use the schedule log to verify several of these. Retained logic or progress override, total float computation, longest path definition, and predecessor calendar use are just a few of the settings which should be reviewed and verified.

The schedule log will also list activities with constraints applied. What it will not do is tell you if the project has a must finish by date applied at the project level. It will also not tell you what type of constraints, (or their dates) are applied to the activities. Again, you must use third party software programs that will report the constraints or you must know how to use the filters, sorting, and reporting functions of the program to see this information.

This schedule log is a very important tool and you should require it with each schedule submission.

What about calendars? How do you verify calendars are assigned? How do you verify the calendars assigned to activities use the correct work days, work hours, holidays? Again, third party software or manually going through the calendars for the project. You can require a pdf layout with the calendar column showing. This will at least let you verify there are calendars other than the default calendar in use.

These are just the basics…. There are other items worthy of validating and I will speak to these in future posts.

I know many of you already know this information and can offer additional guidance and support, for all of us. 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!

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Paul Epperson CCM, PMP, PSP, PMI-SP