The quality of a final project is influenced by a variety of vital, integrated factors ranging from the skill of the people on site and the discipline of supervision, through to the precision of installation. 

But even if care is taken in the delivery, each of these elements can be undermined if the Cost of Quality (CoQ) is not properly managed. CoQ covers the total cost of preventing defects, inspecting work, and correcting failures both during and after a project, to ensure it meets required standards and client expectations. When CoQ is not visible, quality becomes a matter of opinion. When it is measured, quality becomes a managed driver of performance.

Cost of quality is not “extra cost”

Sometimes mistaken for the added expense of doing things “properly,” CoQ instead demonstrates where time and money go. We spend some of it on prevention and verification, but too often we spend far more on failure in the form of rework, delays, claims, waste, and reputational damage. 

When we do not measure this clearly, quality becomes a matter of opinion. When we do measure it, quality becomes a matter of leadership.

Decisions made early shape the true outcome

Long before a defect is logged, the CoQ is already being set by early choices such as scope definition, design coordination, supplier selection, mock-ups, method statements, hold points, inspection planning, and training. 

These are not “overheads,” they are the controls that determine whether delivery stays stable and predictable or whether the project later pays a premium through rework, delay, and waste. 

The key message is simple: if we do not deliberately identify and record both the visible and hidden costs of quality, we will underestimate the true impact of defects and miss the best opportunities to prevent them. 

The consequences go far beyond rework

Recent research shows that defects are not a minor operational inconvenience. They can quickly become a material commercial and safety risk. A 2023 peer reviewed study of 25 building projects found that failure related quality costs exceeded 12% of total project cost. 

Most of that loss was hidden, with visible failure averaging 2.34% and hidden failure averaging 8.59%. The message is clear. If we only record the obvious rework, we will underestimate the real impact and miss the best opportunities to prevent it.

Leadership responsibility: make quality costs visible

For those of us in leadership roles, the opportunity is to build a culture where the cost of defects is scrutinised as closely as technical compliance. That means asking the right questions early, verifying evidence, and not accepting “rework is normal” as a baseline.

A major 2022 “state of science” review shows how averages can mislead. In one contractor dataset, only 210 of 359 projects needed rework. The average rework cost was 0.18% of contract value, yet 48% of the total rework cost came from just 42 projects. This indicates that rework risk is concentrated in a small number of projects rather than being a uniform and unavoidable loss. The same review also describes a Tier 1 contractor case where nonconformance requiring rework resulted in a 27% cumulative profit loss over seven years.

Leadership action is therefore less about “more inspection everywhere,” and more about targeted prevention where risk is concentrated: high-risk trades, repeat defects, weak suppliers, poor coordination interfaces, and rushed design release.

A practical model teams can use immediately

A practical approach can be straightforward. Many organisations classify cost of quality into four groups: 

• Prevention
• Appraisal
• Internal Failure
• External Failure 

Prevention includes planning, training, early coordination, trials, and mock-ups. Appraisal covers inspections, testing, and verification activities. Internal failure captures rework and waste before handover. External failure includes defects after handover, callbacks, claims, and reputational consequences. When these are tracked consistently, leadership gains a powerful lens: not to blame teams, but to remove causes, strengthen processes, and protect delivery.

Linking back to professional standards

CIOB has spent decades promoting higher standards across our industry through competence, professionalism, and a focus on better outcomes. Cost of quality aligns directly with that mission, because it turns “doing the right thing” into a measurable discipline. It encourages long-term thinking over short-term savings, and it supports the wider goal we all share: delivering buildings and infrastructure that are safe, durable, and fit for the future.

If we are serious about improving performance, we must start at the source, not only in what we build with, but in how we fund quality. The choices we make today about prevention, verification, and capability will decide whether tomorrow’s projects deliver value or spend it recovering from avoidable mistakes.

To support this, I recommend that project leaders adopt a simple, repeatable cost-of-quality approach (Prevention, Appraisal, Internal Failure, External Failure) and a short dashboard that links quality outcomes to cost and time impacts. 

Done well, it gives designers, specifiers, procurement teams, and site leaders the tools to make better decisions: clearer risk focus, stronger evidence, fewer repeat defects, and targeted prevention measures that pay back quickly.