The Ugly Truth By CPM: What You Need To Know

In this blog, I’m going to break down some critical flaws with the Critical Path Method (CPM), which I believe has no place in construction today. After working with it for years and creating dozens of CPM schedules myself, I can confidently say that it’s a failed system. 

In fact, I would go so far as to advocate for its removal from schools, project management courses, contracts, and the industry as a whole. It has done more harm than good, particularly when it comes to productivity. Here’s a deep dive into why CPM is a flawed approach.

Why Our Brains Cannot Understand CPM

One of the most glaring issues with CPM is that it’s far too complex for the human brain to process. After creating countless CPM schedules, I’ve realized that by the time you reach five printed pages of activities, even the person who built the schedule loses track of what’s going on. 

If the scheduler can’t understand it, how can anyone else on the team be expected to? This complexity results in a lack of understanding, leaving construction teams to blindly follow a plan they don’t fully grasp.

The Complexity Problem

The second issue is closely related to the first: humans simply can’t manage the complexity of CPM schedules. The system requires tracing ties between activities across vast pages of data, something that would require a computer to track.

 While some might argue that computers can handle this logic through forward and backward passes, the reality is that if the input is flawed, the output will be flawed too. Garbage in, garbage out, as the saying goes.

Misconception About Complexity and Accuracy

Another significant issue is that complexity is often mistaken for accuracy. Owners and clients are easily impressed by these massive schedules, believing that their intricacy guarantees precision. But complexity doesn’t necessarily mean correctness. In fact, the more convoluted the schedule, the harder it becomes to identify mistakes, ultimately leading to poor project execution.

How CPM Hides the Project Plan

With CPM schedules, it’s virtually impossible to get a clear, concise overview of the entire project plan. Unlike a more straightforward Takt production system where the plan is clear and easy to understand, CPM hides the big picture behind pages and pages of data. This lack of transparency makes it difficult to follow the project’s flow, adding confusion rather than clarity.

Unchecked Power of CPM

CPM is deeply embedded in construction contracts, often with no room for flexibility. This unchecked power extends across the industry, from government contracts to legal cases. Unfortunately, this rigidity forces teams into a system that does not allow for the fluidity and buffers necessary in real-world construction. It can lead to unnecessary delays, contractual disputes, and penalization of contractors for issues beyond their control.

Delays and Buffers in CPM

One of the more egregious flaws of CPM is its lack of buffers for delays. The system only accounts for the critical path, meaning that if delays occur outside of this path, contractors are often left without recourse. This lack of flexibility often results in teams being blamed for delays and denied extensions, even when the issues were unavoidable.

How CPM Hides Problems

CPM schedules have a knack for obscuring real problems while flagging issues that may not even exist. Reports generated by CPM often highlight slippage and float trends without providing actionable solutions. Instead of offering strategies to recover from delays, the typical response is to add more labor, work overtime, or increase spending—solutions that rarely improve the situation and usually end up extending the project timeline.

Waste Created by CPM

Another byproduct of CPM’s complexity is the sheer waste it generates. The need for schedulers, owner’s reps, forensic analysts, and legal professionals to manage these convoluted schedules adds unnecessary costs and complexity to the project. All this wasted effort takes attention away from the actual work being done on the job site.

Overshooting and Extending Projects

CPM often incentivizes overshooting work and extending projects. Because of the way forward and backward passes are built into the system, CPM encourages teams to spend more money upfront and push their resources beyond their capacity. This ultimately results in longer project timelines, rather than the efficiency the system was designed to create.

Disadvantages of Not Having Fixed Dates

Another pitfall of CPM is its lack of fixed dates, which results in frequent schedule shifts. Start dates and production targets constantly move, causing unevenness, delays, and unnecessary stops and restarts. This creates chaos on the job site, leading to inefficiency and frustration.

Conclusion

CPM has failed the construction industry in more ways than one. Its complexity, lack of transparency, and rigid structure create more problems than solutions. If you want to improve productivity on your construction site, it’s time to look beyond CPM and embrace systems that allow for flexibility, transparency, and efficiency. I hope this blog gives you the insights needed to steer clear of this outdated system and prevent any failures on your next project.