Hi,

again my Blog reader has a problem:

“Hi,
I have a question about Slack, I am preparing a construction schedule for my small project and using M.S.P. the problem I have is, when I active the slack on the schedule, I realize that on the total slack column, I can not see the total slack for whole project and shows ZERO but on the individual items shows we have slack. How come I can not see total slack on my whole project??? even if I add some more tasks on the critical items again on the top of my schedule ( usually it is name of a project and you can see duration of project, total slack for whole project) show total slack for whole project is again ZERO. Could you please explain me, who can I show on my schedule how many days we have + or – slack for whole project?”

First of all, what is Slack? Slack is available time that Task can be delayed (or extended in Duration) without changing Project Finish date!

Now let me show you in MS PROJECT 2013.First I will create a brand new Project, and I will show it in Detailed Gantt View:

As  you can see Project Start date is Tuesday, 25.11.2014, and Project Finish date is Wednesday, 10.12.2014. The total Duration is 12 Days. Why? Because Task1, Task 2, and Task 3 are on Critical Path! And Critical Path is path on which if any Task will be delayed, the whole Project will be delayed. I will now extend Duration for Task 3 to 8 days:

Now, you can see that Finish date is Wednesday, 17.12.2014, and Total duration is 17 days!

Notice that Task 4, Task 5, and Task 6 have 11 days Slack! So if I extend, for example duration for Task 4 from 1 day to 7 days, I will get:

You can see that Finish date is the same, but Slack time for Task 4 – Task 6 is now 5 days, what make sense.

Task 7 still has 16 days Slack.

Now, why is Total Slack in Project Summary Task (Task #0) = 0. Because Total Slack is not sum of all slacks, but it must be zero because on every Project there is a Critical Path, and on Critical Path, there in no slack! And because there is no slack the Total slack is 0. Btw, what would be, on my example, Total Slack? 16 days (because it is the longest slack on Task 7), or 5 (because it is on Task 4 – Task 6), or 21 (sum of two slacks), or 31 (sum of all slacks). Doesn’t make sense at all to have Total slack for Entire project different then zero.

Hope this helps!