The S-curve is one of the most standard tools in Indian project cost control, and also one of the most commonly reviewed too late - by the time the gap between planned and actual cash flow becomes visually obvious on the chart, meaningful drift has often already occurred and had time to compound.
| Project phase | Typical cumulative variance from plan |
|---|---|
| Mobilisation / early works (first 10-15% of duration) | Usually small - under 5% variance, easy to miss as normal ramp-up lag |
| Main construction phase (25-70% of duration) | Gap typically widens to 10-20% if underlying issues aren't addressed |
| Finishing / handover phase (final 15-20%) | Gap often peaks here - finishing trades compress and cash flow accelerates unpredictably |
Why the Early, Small Gap Is Precisely the One Worth Acting On
A small early variance is genuinely easy to dismiss as normal mobilisation lag - a reasonable-sounding explanation that happens to also be the cheapest point in the project to investigate and actually correct whatever's driving it, before the underlying cause has had time to compound into the considerably larger gap shown in later project phases. S-curve variance should always be reviewed against its actual underlying cause - procurement delay, resourcing shortfall, design incompleteness - rather than simply tracked as an abstract number, since the same 10% variance figure means genuinely different things and requires different responses depending on what's actually driving it.
A Scenario Showing Why Waiting for a Dramatic Gap Is a Costly Mistake
Picture a project where a small, easily dismissed variance appears during mobilisation, attributed casually to normal ramp-up lag without deeper investigation into its actual cause. If the true underlying driver is a procurement delay on a specific long-lead item that hasn't yet been placed on order, that root cause continues unaddressed through the main construction phase, and the variance compounds considerably by the time it becomes visually unmistakable on the S-curve - by which point the procurement delay has already cascaded into schedule impact that's now considerably harder and more expensive to recover from than if it had been investigated and addressed at the small, early-stage variance point.
Why Review Frequency Should Match the Project's Risk Profile
Monthly review is standard practice for most projects, but on schedule-critical or high-value projects, updating the S-curve every two weeks rather than monthly catches drift meaningfully earlier without imposing excessive additional reporting overhead - a reasonable trade-off specifically for projects where the cost of late detection is genuinely higher than the modest extra effort of more frequent review.