From the course: Project Management Foundations: Schedules

Problems with start-to-start dependencies - Microsoft Project Tutorial

From the course: Project Management Foundations: Schedules

Problems with start-to-start dependencies

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- [Narrator] Start-to-start dependencies mean that the start of one activity controls when the other activity begins. A common schedule logic mistake is linking activities with a start-to-start dependency, when they should use finish-to-finish. Here's how start-to-start links can cause trouble. Let's use the writing manuscript and reviewing manuscript example. Each activity is 10 days long. Let's link them using start-to-start and a two day lag. The reviewers start two days after the writers start once they get some pages to review. What if writing takes longer than it's supposed to, let's say 15 days? The reviewing task is still scheduled to finish at the 12 day mark, two days lag and 10 days duration. Now, that's before the writing is complete. That means either some pages go unreviewed or the reviewers have to wait until the writing is done. When you think about it, the correct logic in this example is finish-to-finish. The writing has to finish before the reviewing can finish. With a finish-to-finish dependency, if the writing finish date is delayed, so is the finish date for reviewing. Start-to-start dependencies do have their place when activities must start at the same time. For example, concrete has to be leveled soon after it's poured and before it begins to harden. That's why a poor concrete activity links start-to-start with level concrete. To prevent problems with links, be sure to identify whether the predecessor's start or finish controls the successor.

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