Construction Scheduling. Activity Durations and Unicorns.

When the schedule is developed, (after the project has been broken down and organized into the WBS and the activities have been developed to support the deliverables), how do we determine the duration for each activity?

How do we accurately determine the work period for each activity?

There are several ways this task is approached. Some are better than others….

I believe we can all agree that knowing the required work quantity and production rate per day is the best input we can have to accurately calculate the duration. How often do we actually have that much detail?

More often, the project team determines the durations based on their “feel” for how long the work will take based on similar work from the last few projects. This is not necessarily a bad thing. This is historical data and is very useful.

The problem is that we tend to be optimistic. The larger the piece of work is, the more difficult it is to accurately determine the duration, by “feel”.

Typically, the activities are all developed based on input from the project team, the constrained finish date is applied and then the schedule is “calculated”. Usually, we do not make the required finish date.

Now we start crashing the schedule to pull the finish date back.

We’ve all seen videos of buildings constructed in a week and other supernatural feats. So, it stands to reason that we can build anything within any timeframe, right? If the owner wants the project by the date in the contract, we have to crunch the schedule until it shows we can deliver on time.

As we know, a very high percentage of projects do not finish on time. This often leads to claims and poor performance reviews.

Is it possible that we set our projects up for failure at the very beginning? Do we assume we can provide a finished project within the contract duration just because the owner has specified the period of performance?

If the schedule is constructed using “most likely” durations for all activities with reasonable logic and the project is then constrained to finish on whatever date that produces, there is still a good chance the project will finish late. It could finish early, but that seldom seems to happen.

If the durations are based on pessimistic durations, the project will still tend to use the time allowed leaving little room for problems towards the end of the project.

If we place a contingency activity at the end of the project, we can work towards an early completion hoping we magically finish on or ahead of time.

Or, we can put the effort into building very detailed schedules with solid logic and durations and then execute the projects per the schedules, as well as possible.

Any way you slice it, a poor schedule does not work. An aggressive schedule is not realistic and will soon fall apart, a pessimistic schedule will also fail due to a lack of aggression to complete work.

A detailed schedule, with input from all team members, does not guarantee success, but it does provide a realistic path to get there. It is up to the project team to execute based on the plan. But they can’t do that without a solid schedule.

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