Calendars and Gantt Charts

The last few weeks we’ve looked at a number of different tools to help visualize how long a project will take to complete. A work breakdown structure (WBS) helps visualize the scope of work by breaking a project into chunks that can be effectively estimated and scheduled. PERT charts take that information and add to it information about which chunks need to be completed before others can be tackled (dependencies) to create a picture of the order in which tasks need to be completed. From that information, we can generate an idea of how long the project will take to complete, and see the critical path (CPM) of the work: the sequence of project chunks (or nodes) that must be completed in order because of their dependencies and that has no available slack time. The critical path determines the overall duration of the project.

These tools are all incredibly useful for visualizing the scope of a project—and can be invaluable tools for a technical director who is charged with determining if a particular design can be completed in the time available, and with delivering a project completed on time. However, these tools (as we’ve discussed them) have a major limitation in my view: none of them look remotely like a calendar, and consequently while they convey meaning, they don’t necessarily convey the full impact of the critical path because we’re used to “seeing” time in a particular way.

So how do we resolve this issues? Simple: Gantt charts.

Gantt see the forest for the trees

The most important thing Gantt charts do for us is to provide a visual representation of the duration of work involved in a project in a way that resembles a calendar. This allows for us to get a better overall picture of the project from the detailed information we’ve gathered for each individual node in the project. (And so we can see the forest…well, anyway. If you have to explain a pun, it isn’t funny anyway.)

In the sample Gantt chart below, each row represents a different node from the WBS. The columns represent days, and the colored bars visually demonstrate the duration of each node on the calendar of days. The dashed lines connecting some of the nodes (for example, connecting the nodes “Cut out facing” and “Paint facing”) indicate dependencies. A Gantt chart might also represent the critical path of the project by displaying those tasks on the critical path in a different color (though this example does not).

One of the other advantages of using a Gantt chart is that it can also demonstrate or project progress. In the example below, blue “fill” in each node has been used to indicate to what extent tasks have been completed. If this chart were generated on December 10, it would be clear that we were progressing a bit ahead of schedule. If this chart were generated a week later, on December 17, I’d realize we were falling behind, as we’d not yet started covering the flats with duvetyne.

Used properly, Gantt charts can be used to track schedule slippage and to plan ways to address any slippage. It is easy to see if schedule slippage is happening on critical path nodes; if not, there’s already some slack time inherent in those nodes that can be utilized. If the slippage is happening on critical path nodes, this can be addressed quickly by allocating more resources to those nodes, or by having a conversation about the scope of work required to complete those nodes with the artistic team and reducing it as appropriate (maybe we don’t need three color sprays to finish the floor, and can get away with just two after all, for example).

There are a number of software/webware solutions for project scheduling and Gantt chart generation. Microsoft’s Project software is one; Zoho Projects is a simple, online resource; Tom’s Planner is another. A quick search for “Gantt online” or “Project Planning” will reveal a number of links to other options as well. I hope to put together a review of project management software solutions sometime soon, as well.

Next week: how labor and other resources (like equipment and shop space) can refine the picture even further.