• 20 April, 2022

This article is part of a series that discusses the ten (10) KNOWLEDGE AREAS of the PMBOK, with a practical approach and genuine business examples.

  1. Project Risk Management
    1. Project Risk Management: Part 1
    2. Project Risk Management: Part 2
  2. Project Schedule Management
  3. Project Scope Management
  4. Project Integration Management
  5. Project Cost Management
  6. Project Quality Management
  7. Project Resource Management
  8. Project Communications Management
  9. Project Procurement Management
  10. Project Stakeholder Management

Scheduling is not easy. It involves being very intimate with the project. In many companies scheduling is left for very specialized schedulers. In fact, if you know how to use scheduling tools, you will be extremely popular around your office. But you know that, as with any other software, what matters is understanding the theory. This article will help you understand the fundamentals of scheduling, from both a PMP and practical approach.


1. WBS

A WBS, Work Breakdown Structure, is one of the most important tools that we have in project management, yet it is usually neglected or not well understood. It is definitely most useful when we schedule. Think about dividing all your project scope in work packets or buckets. For example, if you work for a construction company, and you are in a project where you are going to install a brand-new fire detection and alarm system for an existing high-rise building. There are many activities involved in your company providing this product. Are battery calculations part of the same work as installing a smoke detector? Without knowing much, these two seem to be part of the same project, but they belong in separate phases, are part of different milestones, and can be done by different people or roles. This is where a WBS comes in handy.

As always: baby steps. For example, we could start by dividing the project in Engineering, Construction and Commissioning work buckets. These three (3) could be more than enough; it all depends on how complex the project is, but we can certainly keep subdividing and categorizing. Let us see an example:

. Sample WBS for construction; new fire alarm system project
Figure 1. Sample WBS for construction; new fire alarm system project.

The usefulness of dividing your work in buckets or distinct realms is that now it is easy to locate specific tasks, and to assign responsible parties. For example, in Engineering you are expected to produce drawings and calculations. You could just have started to spell out all the tasks required to produce these deliverables, but you can see how convenient it is to keep dividing Engineering in new buckets. For example, at the 15%, you know that you expect to produce a sequence of operations and a coversheet. These two elements can become specific tasks: create coversheet of the drawings, publish a sequence of operations of the system. These specific tasks can be assigned to a project team member, i.e., the project designer. Only when the project designer has finished these two tasks you would consider the project is at the 15% stage, ready to transition to the 30% design stage.


If you have a complete WBS of your project, then it is easy to see the tasks required to produce deliverables in each work packet. These tasks, also called activities, are the events that need to happen to complete the project.

Every work bucket should have associated activities. In our Construction bucket example, we have several subdivisions. For example, to say that we completed Equipment Installation, you know you need to:

  • Receive Equipment on site: control panels, remote panels, and components.
  • Check all equipment conditions.
  • Install equipment according to manufacturer's instructions and shop drawing locations.
  • Label each component and panel.
  • Make final detail connections.
  • Connect power.
  • Turn on the system.
  • Verify functioning of panels.
  • Verify functioning of devices.

Notice how each activity has an action verb associated with it: receive, connect, verify. Activities always represent actions (even if the action is to "wait"). Only when all these activities have occurred, can you say that your Equipment Installation is complete. Conversely, only after SITE PREPARATION, CONDUIT ROUGH-IN, PREFABRICATION, PULL CABLES and EQUIPMENT INSTALLATION milestones are finished, can you say the CONSTRUCTION milestone is complete.


The next step is to find the relationship between activities. Can you install equipment before receiving it? Most activities have a Finish to Start relationship:

  • The activity "Receiving Equipment on site" has to finish before you can start the "check equipment conditions" activity.
  • Only after you finish "connect to power," can you start to "turn on the system."

You can also think of these as predecessor and successor activities. Notice that one activity may have more than one predecessor or successor:

  • "Turn on the system" is a predecessor activity that must be finished before the start of both:
    • "Verify functioning of panels" -successor.
    • "Verify functioning of devices" - successor.

The following are relationships between activities (also called dependencies):

  • Finish to Start, (FS)
  • Finish to Finish, (FF)
  • Start to Start, (SS)
  • Start to Finish, (SF)

We tend to think about relationship between activities as happening immediately, meaning, if two activities have an (FS) relationship, you would think that when the predecessor activity finishes, the successor can immediately start next. This is true most of the times, nevertheless sometimes activities have relationships that include leads and lags, which means, in our example, that a successor activity is set to start at an earlier (lead) or later (lag) date.


This is the headache for most project managers or schedulers. How well can we forecast activity durations? Afterall, schedules are only useful looking into the future, not in hindsight. Schedule, Cost, and Scope make the project baseline. All three elements are necessary to produce a project budget. In other words, the more accurate the schedule, the more accurate your budget is, which is a dream for most project managers.

To estimate activity durations, we can use:

  • Historical company data (how long did the same activities last in previous projects?).
  • Expert judgement (always valuable input from experts).
  • Other estimating techniques, such as Bottom-Up and Three-Point Estimating (PMBOK).

Depending on how detailed your WBS structure is, it could make sense to divide your activities in days, or hours. We had defined that for the Engineering 15% phase, there were two (2) activities. You can look at previous projects and assign durations to each.

  • Create coversheet of the drawings: 16 hours.
  • Publish sequence of operations: 16 hours.

Now, here is a real-life case. These activities do not share any dependency in theory. Creating a coversheet is not related to the start or finish of publishing a sequence of operations, or vice versa. This means that both activities can be done in parallel, at the same time. If this is so, then the 15% of the Engineering phase could be done in 16 hours as total duration. But, if we have only one resource (the project designer) assigned to both activities, then it is most likely that the resource will do one activity first, and then the next, which means the 15% phase will take 32 hours = 16 + 16 hours. If a project manager wanted to expedite the 15% phase, then an additional resource could be assigned to the 15% Engineering phase. This way one resource could "create coversheet" while the other resource works on "publish sequence of operations." The budgeted hours should remain the same (32 hours), but the duration is cut in half, to 16 hours.


Here is where everything comes together. There are many available software tools in the industry that are famous amongst project team members, including Oracle's PRIMAVERA P6, and Microsoft PROJECT. But these tools will not do the work for you of creating tasks, sequencing activities, and estimating durations; this is all up to you.

The most help you will obtain from these tools is a GANTT CHART, which is a type of bar chart. The length of the bars shows the durations of activity and milestones.

Do not get me wrong, you can still create a GANTT CHART yourself in EXCEL, or even by hand! Although the latter would just take a little bit more time to update if there were any changes?.

Example of activities, durations in days, and Gantt Chart with relationship arrows.
Figure 2. Example of activities, durations in days, and Gantt Chart with relationship arrows.

Developing the schedule will provide the following:

  1. An End Date of the project, which is the first thing you want to compare to the client requirements.
  2. A schedule baseline, which will be used to assess progress.
  3. A critical path, where the least amount of time to finish a project is determined, and the critical tasks that, if delayed, will delay the project (the critical path is shown with red bars in Figure 2).
  4. The possibility of assigning resources to specific tasks, especially with the help of scheduling tools. This will provide a resource-loaded schedule, which will speed up creating or updating the project budget.

Regarding schedule and the critical path, the PMBOK offers in-depth study and examples of how to create relationships, and how to use the critical path method. The PMP exam always has a couple of questions about this subject.


Setting up the schedule is one thing, keeping up with it is another! Progress on project activities must be compared against the schedule baseline to understand if the project is ahead, behind, or on schedule. Being ahead is always good... but being too ahead will give the impression that you did not do a decent job estimating. Still, being ahead for the right reasons is always a blessing to clients. Project delays are one of the things that kills relationships with loyal clients, in this humble author's opinion.

The project may start getting behind. As I always say, this fact alone will not condemn a project manager; it is how the project manager reacts to changes. As always, communication is the project manager's biggest ally. If the schedule is behind, the project manager can initiate corrective actions to bring back the schedule to the baseline. Sometimes this is possible without compromising additional resources (remember the example in section 4 about assigning a second resource to the 15% Engineering phase? The budgeted hours remain the same, and the duration was cut in half). But other times the project manager faces a tough choice: was the delay caused by someone's negligence? Is the event worth initiating a change control process? Should the project manager assume all costs? Should the project be delayed, or should unplanned resources be spent returning the schedule to its original baseline?

As always, it depends. But by having the correct processes in place and knowing the fundamentals, the project manager will be prepared to make the decision with the right information at hand.

About the Author: Alejandro Uribe

Alejandro Uribe got his strong process approach from Industrial Engineering (B.A.), his vocation in Construction Management (M.S. from NYU), and his real passion in Fire Protection (P.E.), where he continues to provide complex solutions to Fortune 500 Companies and critical federal projects. Alejandro is currently an engineering manager at M.C. Dean, a prime contractor, where is the supervisor and technical lead for a team of over 12 engineers, and is responsible for creating and maintaining processes, including knowledge management and project management foundations

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