Steps for Doing a Gantt Chart

1. Put a list of the tasks (from your network diagram chart) down the left side, with the critical path tasks listed at the top.

2. Put the weeks necessary for the project across the top (you know this because you have already worked out the critical path - with contingencies - and that amount tells you how long the project will take.)

3. Next, you will put in the critical path steps/tasks (in red), with each step/task in the sequence cascading down, from one task to the next (one right after the other, since there is no slack between because this is the critical task.)  Note that you will put in the person hour times for each of the tasks during the proper week and, if you crashed your critical path, you can easily show where that happens (mine is found at weeks 28 through 30, where there is an overlap between purchasing the site and modifying the building.)  With that, I saved a couple of weeks.

4. Next, we put in the floating tasks (in green), one at a time, as shown here.  For each task I have put in vertical lines, showing the limits for each task's movement or float.  This includes placing it in a spot that shows what each task must come after and what each task must come before.  For instance, 'Finding the Site' must wait until after we have chosen the location, and it also must be done before we purchase the site, so that is the range it must be fit into (since it has float, I can decide whether to do it earlier or later; I have flexibility.)



Linked to these are two slight variations when it comes to the floating tasks - each are on display in the example here.

One is the sharing of float.  'Hiring the Manager' and 'Buying Furniture' both fit between 'Choose Location' and 'Install Furniture,' so they share that space (that is, neither of them butt up against either the beginning of the project or the end of the project.)

The other is floaters that depend on other floaters (this is differentiated by the "sharing of float" variety because it terminates at the end of the project.)  'Hire Staff' (a floater) is hanging off of 'Hire Manager' (also a floater).  Both of these can float so they both can be done earlier or later - you just add them in, one after the other, with vertical lines coming off of the previous tasks.

Once you understand these two variations (and they are quite similar to each other), you can build any size Gantt chart.

And, underscoring a very important point, since everything hangs off of the critical path, you perhaps now can see why it is so very important to do your network diagram beforehand - that gives you deep insight into the nature of your critical path.