The PMC Perspective · Cost Control
The arithmetic of cost overruns, plainly stated
Cost overruns rarely arrive as one dramatic event. They accumulate through a repeatable set of quantity, rate, productivity, time and scope variances—often visible months before the forecast acknowledges them.
Published 2026-07-29 · 8 minute read · By Asad Hatimi
A cost overrun is usually a stack, not a surprise
On a major industrial project, the approved budget is exposed to several arithmetic systems at once. Quantities change as engineering matures. Rates move through procurement. Productivity changes the labour and equipment hours required. Time adds overheads, escalation and financing exposure. Scope decisions create new obligations. Claims convert unresolved interfaces into money.
The management error is to discuss these movements as one variance. A single forecast-to-complete number hides the mechanism. Effective control separates the stack, assigns ownership and shows how each variance can still change.
The ten recurring variance patterns
The most common patterns are quantity growth, rate variance, productivity loss, schedule prolongation, scope creep, design development, rework, interface and access loss, commercial claims, and premature contingency drawdown.
Each pattern requires a different countermeasure. Quantity growth needs design maturity and reconciliation. Rate variance needs sourcing strategy and package discipline. Productivity loss needs work-front and crew analysis. Prolongation needs critical-path recovery. Treating every variance as a procurement problem or demanding a general cost reduction usually transfers risk rather than removes it.
Forecast the remaining work, not the approved hope
The estimate at completion should begin with actual commitments and actual performance. Remaining quantities must be priced at credible rates. Remaining hours must reflect demonstrated productivity unless a documented intervention changes it. Time-related costs must follow the schedule forecast rather than the contractual milestone.
This is where cost and schedule control become one discipline. A completion date that moves without a corresponding cost movement is a warning that the forecast systems are disconnected.
Make contingency visible
Contingency is not an informal balancing figure. It represents defined uncertainty and should be governed through drawdown rules, named risk events and remaining exposure. When contingency is consumed to hide known scope or performance variance, leadership loses the buffer intended for genuine uncertainty.
A useful board view shows opening contingency, approved drawdowns, pending requests, quantified residual risk and the confidence range around the forecast.
The countermeasure that changes behaviour
The most effective cost review is a monthly reconciliation of budget, commitments, incurred cost, physical progress, schedule forecast, risk and change. The conversation should centre on movement since the previous forecast and the evidence behind it.
Plain arithmetic creates accountability. It identifies which part of the overrun has already happened, which part is committed, which part remains exposed and which management decision can still protect value.