Building and Using Slack in Microsoft Project 2007

Building and Using Slack in Microsoft Project 2007
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This is Part Two in a two-part article series. Click here to read this series from the beginning.

Build Slack

You can build free and total slack into your project plan in a couple of ways. One of the things you can do to build in some slack is to change the relationship between two tasks. As you look at your project plan file, you might have a finish-to-start relationship between two tasks, as shown in figure above.

Go Back to Gantt Chart View

Change relationships to lessen project time

To get back to Gantt Chart view and the Entry table, choose View and then Gantt Chart, and then choose View, Table, and then Entry.

Upon further investigation, you discover that those two tasks could probably be completed at the same time. In this scenario project managers typically try fast-tracking (which is overlapping tasks). Another option is that, instead of using a finish-to-start relationship, you can instead assign a start-to-start relationship or a finish-to-finish relationship—a relationship that would allow those tasks to occur simultaneously, as shown in the figure above.

If two tasks have the same resources, you might need to do some playing around with the schedule by assigning a different resource to one of the tasks so that those two tasks can happen at the same time.

Another option for building some slack into your project schedule is to actually remove a task or a task requirement. However, use this method only if removing a task requirement will not affect your project scope. Or, if your project scope is affected, be sure to ask the stakeholders for permission before making the modification. You certainly do not want to remove important tasks from your project schedule all in the name of building some slack into the project plan file.

Finally, you can modify Office Project 2007’s default slack option by changing the number associated with slack. Office Project 2007 governs by the rule that marks a task critical if the task has zero slack. But you can change that slack number in the Calculation tab of the Options dialog box. This should be an option only if your company and project stakeholders agree to the change.

Set When Tasks are Critical

In this way you tell Office Project 2007 that a task is not critical unless it has one day of slack (or a different duration of your choosing). In other words, a task is not critical unless it is going to change the project’s end date by one day (or whatever that number is for you). Essentially, you can change the amount of slack required for a task before Office Project considers it critical. Follow these steps:

  1. Choose Tools and then Options.
  2. Click the Calculation tab.
  3. At the bottom, change the amount of slack required before Office Project considers the task critical using the spin box.
  4. Click OK.


There are two types of slack: free slack and total slack. Free slack is the amount of time you can delay a task before that task will affect or delay another task. Total slack is the amount of time you can delay a task before that task delays the actual project completion date. A task is on the critical path if its total slack is zero (by default). However, you can use the Options dialog box to change that number to any number that best suits your project planning methods.

Office Project 2007 is constantly recalculating the critical path in the background. Even if you never choose to format the Gantt Chart using the Gantt Chart Wizard, you can also see tasks that have slack in them on the Detail Gantt view and the actual numbers associated with slack in the Schedule table.

Excerpted from…

With permission from Microsoft Press, this article content was excerpted from the book, Managing Projects with Microsoft Office Project 2007 (Self-Paced Training Kit for Exam 70-632).

This post is part of the series: Project 2007: Using Slack

A step-by-step guide to using Slack in your Microsoft Office Project files.

  1. Project 2007: Using Slack (Part 1 of 2)
  2. Project 2007: Using Slack (Part 2 of 2)