Construction Scheduling Made Easy: Master PERT for Success

Written By michael donaghy

Meeting deadlines, staying within budget, and delivering high-quality projects are mandatory for a successful project, right?
But how is it exactly that you achieve that? Well, A PERT can give you a big edge.

It doesn't matter if you're a seasoned project manager or starting your journey.
There’s a reason this tool is widely loved.

Keep reading and find out everything you know about it!

II. What is PERT?.

The 1950s witnessed the dawn of the nuclear age, and the U.S. Navy embarked on the ambitious Polaris ballistic missile submarine program.

This project demanded a high level of complexity and precision in scheduling and managing tasks.

Existing project management methods, like Gantt charts, struggled to account for the inherent uncertainties involved in such groundbreaking endeavours.

Sample of a Gantt chart used in a construction project

In response to this challenge, the U.S. Navy's spearheaded the development of PERT.

PERT's core concept lies in acknowledging the inherent uncertainty in project task durations and incorporating this variability into project planning

It uses three time estimates for each task:

  • Optimistic Time (T_o):
    The shortest possible time a task can be completed under ideal circumstances
    i.e:
    -Favourable weather conditions
    -No material delays.
    -Complete crew requirement

  • Most Likely Time (T_m):
    The most realistic estimate of how long a task will likely take, considering typical conditions.
    -Unsteady weather
    -Some material delays.
    -Complete crew requirement

  • Pessimistic Time (T_p):
    The longest conceivable time a task could take due to unforeseen delays

    i.e:

    -Severe weather
    -Equipment breakdowns
    -Skill Shortage

It's important to differentiate PERT from the Critical Path Method (CPM), another popular scheduling tool.

While PERT focuses on probabilistic time estimates, CPM assumes deterministic durations for tasks.

This makes PERT more suitable for projects with inherent uncertainties, which is often the case in construction

III. How Does PERT Work in Construction?



Let's take a step-by-step approach to implementing PERT for a construction project, using the familiar example of building a house:


  1. Identify Tasks and Dependencies:

    Break down the project into smaller, manageable tasks. Analyze dependencies – tasks that need to be completed before others can begin (e.g., foundation work must be finished before framing can start).


  2. Estimate Task Durations:

    Assign optimistic, most likely, and pessimistic durations for each task. Consider historical data from similar projects, resource availability
    (e.g., skilled labor, materials), and potential risks (e.g., weather delays, permitting issues) when making these estimates.


  3. Calculate Expected Duration:
     Use the PERT formula: Expected Duration = (T_o + 4T_m + T_p) / 6.
    It gets the weighted average duration for each task.

    This formula assigns a higher weight to the most likely time, reflecting a more realistic scenario.


  4. Construct a PERT Chart:
    - Use project management software with PERT functionality or a simple
    manual approach.
    -Draw boxes to represent tasks and arrows to depict dependencies between
    tasks.
    -Common symbols can enhance clarity: circles for milestones (significant
    project markers) and diamonds for decision points (points where project
    flow might change based on a decision).


  5. Identify the Critical Path:
    Analyse the PERT chart to identify the critical path – the longest sequence of dependent tasks.
    Delays in any critical path task will directly impact the entire project schedule. For instance, if foundation work (critical path task) is delayed due to bad weather, framing and subsequent tasks will also be delayed.


  6. Analyze Risks:
    PERT lets you find critical tasks. This lets you spot bottlenecks early and make plans to avoid delays.
    For example, identifying permitting as a critical path task might prompt efforts to hurry the permitting process.

IV. Benefits of Using PERT in Construction

The advantages of using PERT in construction are numerous. Let's explore some key benefits:

  • Improved Project Planning: PERT facilitates realistic project timelines by considering uncertainties. This allows for more accurate resource allocation and reduces the risk of schedule overruns.

  • Enhanced Resource Allocation: By understanding task durations, project managers can assign resources (labor, equipment) effectively.
    This ensures critical tasks have the necessary resources to stay on track.

  • Risk Mitigation: Identifying the critical path helps prioritize tasks and prepare for potential delays.

    Proactive measures can be taken to address potential risks associated with critical path tasks, minimizing their impact on the overall. This minimizes their impact on the project's schedule and budget.

    For instance, having backup suppliers for materials helps. Identifying alternative labor sources does too. They can mitigate delays from unforeseen disruptions.

  • PERT helps control costs.
    It finds delays that could cause cost overruns. By understanding the impact of delays on critical path tasks, project managers can implement cost-saving measures or adjust budgets accordingly.

  • PERT charts improve communication.
     They help team members talk about project progress and dependencies. Visualizing tasks and their relationships helps people understand the project flow and possible bottlenecks. This allows for better collaboration and quicker decision-making when issues arise.

Studies by the Project Management Institute (PMI) have shown that PERT projects are more likely to finish on time and on budget.
This is compared to those who use traditional scheduling methods.

V. Limitations of PERT

While PERT offers significant benefits, it's important to acknowledge its limitations:

  • Reliance on Estimates: The accuracy of PERT heavily relies on the quality of the initial time estimates. Inaccurate estimates can lead to an unrealistic project schedule. For this reason, involving experienced personnel in the estimation process is crucial.

  • PERT can struggle with very complex project dependencies. This happens when there are many interconnected tasks. In such cases, alternative scheduling methods like Monte Carlo simulations might be more suitable.

  • Focus on Time, Not Resources:
    PERT primarily focuses on scheduling tasks and identifying the critical path. It provides a framework for resource allocation. But, it lacks detail on leveling or constraints.
    There you have it!

    Whether you're managing a complex construction project or streamlining a marketing campaign, PERT offers a valuable tool to navigate uncertainty and achieve success.


So, next time you face a project with variable timelines, consider incorporating PERT. With its ability to identify critical paths, build in buffer time, and adapt as you go, PERT can be your secret weapon for bringing projects to fruition on time and within budget.




Are you a construction company that wants to improve project management? Or, are you a Quantity Surveyor or Cost Estimator seeking exciting career opportunities? Visit our website at https://www.gedonexecutive.com to learn more.

References

michael donaghy
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