Month: April 2017

Construction Scheduling. Total Float Values and Calendars.

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

Construction Scheduling. Let Durations Help You.

How can you use the Activity Duration value to help you manage your schedule?

Simple, just look at all the columns and do some math in your head.

When your contractor develops the project baseline schedule, they develop the Original Duration for each activity. How they develop the durations is a subject for another post. But let’s assume they have used historical data, input from subcontractors, calculated productivity and quantities, or some method of developing an accurate value for the each Activity’s Original Duration.

Most Schedule Presentations (Gantt Chart pdf’s) have the activity names, dates, a percent complete and a duration for each activity shown in columns. Then there are the magical bars to the right. Sometimes there are even relationship (logic) lines drawn from activity to activity so you know what drives what, right? Can you actually read it? Doubtful…. Anyway, let’s focus on the duration columns.

If you’re looking at a Schedule Presentation from a Primavera P6 schedule, there are options for which duration columns you can see. Almost everyone uses the Original Duration column. Most of us use the Remaining duration column. That’s all we need to know, correct?

Not really, there is a column that shows the At Completion Duration. This is not seen in presentations that often, probably because we want more room for the magic bars and lines… But this is an important column to be able to see when reviewing a Schedule Presentation pdf.

If you have an Original Duration of 5 days (Work Days or Calendar Days depends on the Calendar. This is a subject for another post), and a Remaining Duration of 3 days and the percent complete (whether it is Physical, Duration, Activity, Performance, or Cost or another type is a subject for another post), is 50%, things are looking good, right?

Not always. If you look at the At Completion Duration, you may find that while the Original Duration is 5 and the Remaining duration is 3. But the At Completion Duration could be 35 or any other value if the activity finish date is riding the Data Date. This can happen depending on the settings used to manage the schedule. Unless you actually look at the dates and do some calculations in your head while reviewing the schedule, when you don’t have the At Completion duration column to use, you may not see the slippage.

Ask your contractor to display the At Completion Duration column for their Progress Meeting Look Ahead Schedules and any other pdf submission. It’s worth the trade off with the magic bars and lines!

Knowing what was planned, what is remaining and what the time impact of activity progress slippage is can save you some trouble.

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