Introduction to CPM Scheduling: Part 3

The Levels of CPM Schedules, Baseline Schedules, and Eight Core Rules of CPM Scheduling to Make a Project Successful

(Part 3 of Introduction to CPM Scheduling)

In Part 1, we broke down what CPM scheduling is and why it matters. Part 2 took a deeper dive into the benefits, components, and common scheduling activities. Now, in Part 3, we’re pulling the curtain back on how to use CPM scheduling in a real-world setting. We are going to dive into the levels of detail you’ll work with and touch on the baseline process. We will also look at some rules that must be followed and how all of this actually helps your project succeed.

Like always, I’m not here to throw a bunch of technical lingo at you. This 3-part series is meant to be understandable, human, and hopefully useful whether you’re a GC, subcontractor, or PM. If you are someone just trying to understand CPM Scheduling in general, then don’t skip Introduction to CPM Scheduling Part 1 and Part 2. With that being said, let’s get to it.

Levels of CPM Schedules

Not all schedules are created equal, and of course, they shouldn’t be. Depending on who’s using the schedule and what stage the project is in, different levels of detail are needed. Let’s take a look at a breakdown of what I am talking about:

Level 1: Project Summary Schedule

This is your high-level overview. Think of it like you are looking at a roadmap with only the major cities. The project summary schedule will cover contract milestones, start and finish dates, and the key deliverables. This version will most likely be seen in executive meetings or project proposals.

Level 2: Project Phase Schedule

Now, we’re getting into the bones of the job. Thinking back to the roadmap, these are the roads that interlink to each major city. This level breaks the project down into major phases like mobilization, structure, envelope, interior rough-ins and finishes, etc. This schedule is most useful for planning how trades hand off work and when each phase will start and end.

Level 3: Detailed Phase Plan

Here, we start slicing up each phase to see how it plays out in real time. Each primary phase gets its own sequence of activities, typically aligned with trade-specific scopes. This would be like taking each major city and planning out each road. You should begin scheduling the road build with civil engineers, road paving crews, utility crews, and specific trades such as bridge construction teams. The idea of this detailed phase plan is simply coordination. This makes the process much easier when everyone can see where they fit.

Level 4: Detailed Schedule

This is your boots-on-the-ground view. Think back to the road map and pretend you are dropped down smack in the middle, yet you can see all things broken up into specific areas. This schedule supports all coordination daily and is the version you will use for looking ahead, weekly meetings, and tracking the critical path within the project.

Using the Detailed CPM Schedule for Planning

Think of this as the “Grand Plan.” Like all things scheduled and broken down into a script for a movie. A detailed CPM schedule will translate plans and drawings into a real-time execution. That process starts with identifying activities based on scope and placing those tasks in order, like what has to happen first and what can run in parallel with each other. These activities are actions such as pouring concrete, doing rough-ins, or inspections. As the project progresses, this schedule becomes the backbone of planning meetings and coordination sessions. This is the actual strength of your project’s successful completion. 

Baseline Schedules

The baseline is based on your contract obligations. This is the schedule snapshot that says, “This is how we said we were going to do it.” This is the base of your plan to begin execution of the project. 

How to Create a Baseline Schedule

With all of the above steps completed this is just as simple as it sounds. Once the CPM schedule is built and reviewed by all stakeholders involved you then set it as the baseline. This snapshot becomes the benchmark to measure against throughout the duration of the project. Read more.

Elements of a Good Baseline

Although the baseline is simple at this point there are still some things to incorporate to make the baseline good standing. Let’s take a look at the elements involved in a good baseline.

A good Baseline will have the following:

• Activities are realistic, cover the complete scope, and reflect actual construction methods.
• Logic ties that make sense. (no floating or unlinked tasks)
• All Calendars match field working hours.
• Include major milestones that are tied to contract obligations.
• Includes all important procurement and preconstruction items.

Why Update the Baseline Schedule

Many things uncounted for can happen and will happen. Schedules are living tools, and like all living things, they need updates. Projects will alter for many reasons, such as the weather, mandatory inspections, material delays, manpower issues, or anything else that could cause a schedule shift. If you’re not updating your schedule, your crew is navigating in the dark with no headlights. Imagine driving down the interstate in pitch dark without any lights. That could be a disaster. Updates let you see the ripple effect of delays and help you manage recovery. 

Updating the Schedule

Depending upon the project, its size and time frame, the update frequency (weekly/monthly) will be decided. Monthly updates are definitely advised. However, if the jobs need close monitoring then weekly updates are advised. The process of update includes putting in actual start/finish dates, progress percentages, revised durations, and logic adjustments if needed. When the update is completed, analyze the critical path and review progress against the baseline.

Reviewing the Critical Path

Keep an eye on which path is now driving the project. If the critical path has changed, make it a priority to understand why. Even one shift could strike a red flag, or it may just be a logical result of early finishes elsewhere. Reviewing the Critical Path is not only important but a key to success.

Things to Remember About Updates

There are a few things to remember about updates, and they should become embedded knowledge to act upon in every project. Let’s take a glance:

• Always review float trends and remember that negative float means trouble is brewing.
• Don’t forget non-critical activities. If you are not watching, they may become critical.
• Keep consistent naming conventions so your reports stay clear.
• Back up every version because disputes and delays do happen. Trust me, you will thank yourself for doing so.

Useful Reports from CPM Schedules

Reports from CPM Schedules are very important and have many uses. Let’s take a look at some useful reports:

• Look ahead reports by 2-4 weeks
• Variance reports of the Critical Path
• Total float trends report
• Planned vs. actual bar charts
• Manpower and resource curves

These reports don’t just inform; they empower you and your team to make decisions instead of guesses.

Eight Core Rules of CPM Scheduling

Here’s the unspoken rulebook that separates the “just okay” schedules from those that work in the field.

1. Activities: Enough Detail, Not Overkill

Include enough information to track work, but don’t turn your schedule into a task list. Leave it out if the activity doesn’t drive time, cost, or coordination.

2. Logistical Restraints Matter

Don’t schedule pipe installation in a hallway while drywall’s going up. Real-world sequencing based on space, equipment, and access should shape your schedule.

3. Preferential Restraints Help (When Used Wisely)

Just because a tie isn’t mandatory doesn’t mean it isn’t useful. Use preferences to make your plan flow better, but don’t lock yourself into unnecessary restrictions.

4. Date Constraints Only on Contract Activities

Apply constraints on milestones or contract obligations only, not every little task. Let logic do the work for most activities.

5. Start-to-Start Usually Needs a Finish-to-Finish

If you link two activities to start together, you often need them to finish together, too. Otherwise, you’ll end up with some strange gaps.

6. No Lags in Finish-to-Start

Lags are tempting, but they’re hard to track. Use more detailed activities instead so you can see what’s actually happening in the field.

7. Include Preconstruction Activities

All Permits, design approvals, and submittals matter. If they are not in your schedule, delays will magically throw a rock in your spokes later on.

8. Not All Critical Path Activities Are Equal

Just because something’s on the CP doesn’t mean it’s high risk. Some critical activities are short or easy to recover. Others are long-lead or high-cost. Learn the difference and focus your attention where it really counts.

How Can a CPM Schedule Help Make a Project Successful?

These reasons should be apparent by now, and the part where theory meets practice can clearly be seen. Let’s endeavor in a short refresher anyway:

A good CPM schedule:

• Brings clarity to everyday chaos.
• Helps the team stay in alignment.
• Tracks progress in real-time.
• Allows you to plan manpower and materials proactively.
• Protects you when delays happen because of already documented progress.
• Increases understanding and faster decision-making.
• Builds trust with owners, GCs, and subcontractors.

Things to Remember About CPM Scheduling

• It’s a living document that needs to be updated frequently, not a one-time exercise.
• The more involved your team is in the schedule, the better things will flow.
• You don’t need to be a scheduling expert; you just need to understand how the flow needs to go.
• A solid CPM schedule is like a GPS; it shows you where you are and where you are going.
• If something looks off, do not ignore it; question it. As in any profession, the best schedulers don’t assume; they always clarify and verify.</span>

Wrapping Up

That’s a wrap on Part 3 of our Introduction to CPM Scheduling series. Now, you should have a basic understanding of CPM Scheduling and are beginning to see its value. If not, then maybe you missed Part 1 and Part 2 If this is the case, then I strongly urge you to read them to gain as much knowledge as you can for your next project. It doesn’t matter what you are managing, high-rises or hospital retrofits. Projects big or small, easy breezy, or hard and chaotic, CPM scheduling gives you control.

Imagine having complete control over time. One of your most valuable and limited resources is under your control.