Blog Title
Published June 2021, Updated April 2023
Published September 2022, Updated April 2024
S-Curve from a Construction Schedule (with Examples)
The S-Curve tells you when to expect the greatest and smallest billings throughout the project.
Learn more about schedule cost loading here.
Summary
The S-Curve is a graph that shows a project’s planned versus actual progress, measured by earnings. It tells you the following:
Project Status. The S-Curve provides a quick snapshot on the earnings health of your project – if earnings are ahead, behind, or on target.
Schedule Deviations. Differences between the planned versus actual curves indicate deviations in your project schedule. If you observe deviations from the planned versus actual in your project’s S-Curve, make sure you understand what caused it.
Cost Loading. Since the S-Curve captures earnings over time, it visually shows you the schedule’s overall cost distributions. The S-Curve tells you when to expect the greatest and smallest billings throughout the project.
By understanding these concepts, you can leverage the S-Curve as a quick communication and visual tool in your project.
Questions or comments? Reach us at connect@cpm-ss.com.
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The example below shows a project with low costs until the end of the project. This could be due to:
- A long planning or design period early on with relatively low costs compared to the construction period.
- Long lead and high dollar procurement with delivery and installation near the end of the project.
What the S-Curve Tells You
If you observe deviations from the planned versus actual in your project’s S-Curve, make sure you understand what caused it.
Other S-Curve actual versus planned deviations to look out for include drastically flatter or steeper curves, bumps, spikes, or stagnation.
What the S-Curve Tells You – Cost Loading
Since the S-Curve captures earnings over time, it visually shows you the schedule’s overall cost distributions.
The example below shows a project with high costs early on. This could be due to:
- Cost front-loading as explained in our Schedule Cost Loading article.
- Short start-up or project planning time.
- Early accelerated schedule.
As these examples show, the S-Curve provides a quick snapshot on the earnings health of your project – if placement is ahead, behind, or on target.
Additionally, if your project schedule is showing on-time completion but your S-Curve is showing delay – let this serve as a red flag with more investigation needed.
What the S-Curve Tells You – Schedule Deviations
Differences between the planned versus actual curves indicate deviations in your project schedule.
As an example, the snapshot below shows a project about halfway through its duration.
During the early part of the project, the actual (green) curve fell behind the planned (blue) curve – meaning there was a delay. The actual curve then however became steep and moved in front of the planned curve.
In other words, the project fell behind in the beginning but then turned around quickly and is now ahead of schedule.
Now notice in the example below, the actual earnings (green) curve is to the right of the planned earnings (blue) curve. This means there were actual earnings later than planned, or behind schedule.
A project’s S-Curve communicates the pace of work and progress throughout the project.
In construction, the S-Curve is a graph derived from the cost loaded schedule and compares planned versus actual progress.
Understanding how the S-Curve works and what it tells you allows you to leverage it as a quick visual communication tool.
The S-Curve is additionally required with each schedule submission for military and federal projects using the standard UFGS 01 32 01.00 10 scheduling specification.
In this article, we discuss::
- What is a S-Curve from a Construction Schedule?
- What the S-Curve Tells You:
- Project Status
- Schedule Deviations
- Cost Loading
What is a S-Curve from a Construction Schedule?
The S-Curve is a graph that shows a project’s planned versus actual progress, measured by earnings.
Time is plotted on the X-axis, and earnings on the Y-axis.
What the S-Curve Tells You – Project Status
A S-Curve will tell you if the project’s earnings are ahead of schedule, behind schedule, or on target.
As an example, the snapshot below shows a project’s planned (blue) and actual (green) curves to date, about halfway through the project.
Notice the actual earnings (green) curve is to the left of the planned earnings (blue) curve. This means there were earnings earlier than planned, or ahead of schedule.
The name comes from the S-like shape of the curve. The nature of the curve changes with the following project periods: See the snapshot below with the purple, blue, and orange portions of the curve.
Start-Up Period: The curve has a flat to low slope with a gradual increase since the project is just starting up.
Construction Period: The curve is steepest with the greatest amount of work and earnings taking place during this time.
Closeout Period: The curve flattens out again with lower amounts of earnings during closeout.
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This blog is for general informational purposes only and is not to be considered an official interpretation or enforcement policy of the UFGS standard specifications. As individual project requirements vary, refer to your specific contract. See our Terms and Conditions and Disclaimer for additional information.
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