Quality Assurance vs Quality Control: QA vs QC Explained

Quality Assurance and Quality Control are two terms that are regularly used together—and just as regularly confused.

They are often combined into the abbreviation “QA/QC”, especially in construction, engineering and manufacturing. This can make them sound like one activity, one department or two different names for the same thing.

But they are not the same.

Quality Assurance (QA) is mainly concerned with preventing quality problems by establishing effective processes, responsibilities and controls.

Quality Control (QC) is mainly concerned with checking the resulting work, product or service to determine whether the specified requirements have actually been met.

To put it very simply:

QA tries to prevent problems.
QC tries to identify problems.

That does not mean QA happens only before the work and QC happens only afterwards. Both may continue throughout the lifecycle of a product, service or construction project.

They are different, but they depend on each other. Quality Assurance without Quality Control can create a beautiful system that nobody verifies. Quality Control without Quality Assurance can result in people repeatedly finding the same problems without improving the process that caused them.

So, let’s have a detailed look at the differences between Quality Assurance and Quality Control, with practical examples of how they work together—and, because this is Quality In Construction, how they are actually applied on a construction project.

Quality Assurance vs Quality Control at a glance

Difference	Quality Assurance (QA)	Quality Control (QC)
Main purpose	Prevent quality problems	Identify quality problems
Main focus	Processes and systems	Products, services and completed work
Approach	Preventive and proactive	Detective and corrective
Typical timing	Before and throughout the work	During and after execution
Typical activities	Planning, procedures, training, audits and process reviews	Inspections, tests, measurements and acceptance checks
Main question	Do we have an effective process?	Does the result meet the requirements?
Typical evidence	Plans, procedures, audit reports and training records	Inspection records, test results, checklists and NCRs
Construction example	Establishing an ITP and inspection process	Inspecting reinforcement before concrete is poured

This is the basic difference, but the reality is slightly more complicated. QA and QC overlap, and the information produced by one should influence the other.

What is Quality Assurance?

Quality Assurance is the part of quality management that provides confidence that quality requirements will be fulfilled.

It focuses mainly on the processes, systems and arrangements used to produce the required result.

Quality Assurance asks questions such as:

Have the requirements been identified?
Are responsibilities clearly defined?
Do we have suitable procedures?
Are competent people carrying out the work?
Are documents and drawings properly controlled?
Are suppliers and subcontractors being evaluated?
Have inspections and tests been planned?
Are problems being investigated properly?
Is the system actually being followed?
Are we learning from previous failures?

Quality Assurance is therefore wider than inspection. It tries to create the conditions in which compliant work can be produced consistently.

On a construction project, QA activities may include:

Preparing the Project Quality Plan
Establishing quality procedures for the construction project
Defining roles and responsibilities
Reviewing contractual and technical requirements
Evaluating subcontractors and suppliers
Preparing and approving method statements
Planning inspections and tests
Approving document-control arrangements
Training and briefing the project team
Conducting internal audits
Reviewing quality performance
Investigating recurring problems
Implementing corrective actions

A good QA system should not become a mountain of paperwork that nobody reads.

The objective is not to produce procedures simply to satisfy the client or an external auditor. The objective is to establish practical controls that help the team deliver compliant work without unnecessary mistakes, confusion or rework.

What is Quality Control?

Quality Control is the part of quality management that focuses on fulfilling quality requirements.

It involves checking, inspecting, measuring and testing the actual product, service or completed work.

Quality Control asks questions such as:

Does the work comply with the approved drawing?
Does the material meet the specification?
Is the dimension within tolerance?
Was the required test completed?
Were the acceptance criteria achieved?
Is the workmanship acceptable?
Can the activity proceed to the next stage?
Does a nonconformance need to be raised?

Typical QC activities include:

Visual inspections
Dimensional checks
Material inspections
Laboratory testing
On-site testing
Sampling
Functional testing
Witnessing hold points
Reviewing test certificates
Checking completed records
Snagging inspections
Final acceptance inspections

QC does not necessarily mean waiting until the product is finished.

In construction, waiting until the end is often too late. Reinforcement becomes covered by concrete, services become hidden behind walls and waterproofing becomes inaccessible beneath finishes.

Quality Control must therefore take place at the correct stages while the work is still accessible and while problems can still be corrected without unnecessary demolition or rework.

What is the main difference between QA and QC?

The main difference is their focus.

Quality Assurance focuses on how the work will be managed and performed.

Quality Control focuses on whether the resulting work meets the specified requirements.

QA is usually described as process-oriented, while QC is usually described as product-oriented.

QA is preventive because it establishes arrangements intended to stop problems from happening.

QC is detective because it checks whether a problem has occurred despite those arrangements.

But we need to be careful here.

QC is not simply a reactive activity carried out after everything has gone wrong. A well-planned inspection can detect a problem early enough to prevent it from affecting later work.

Similarly, QA is not automatically effective just because procedures exist. A procedure that does not reflect how work is actually performed provides very little assurance.

Quality Assurance examples

The easiest way to understand QA is through practical examples.

QA example 1: Establishing a construction inspection process

Before construction begins, the project team defines:

Which activities need inspection
Which inspections require client attendance
Which records must be completed
What the acceptance criteria are
Who is responsible for each inspection
What should happen when work is rejected

This is Quality Assurance because the team is establishing the process that will be used to control quality.

QA example 2: Evaluating a concrete supplier

Before placing an order, the contractor evaluates the proposed concrete supplier.

The evaluation may consider:

Technical capability
Previous performance
Mix-design experience
Production controls
Testing arrangements
Calibration records
Delivery capability

This is QA because the contractor is trying to reduce the risk of receiving unsuitable concrete before production starts.

QA example 3: Training site personnel

A project introduces a new waterproofing system. Before installation, the operatives receive training from the manufacturer and the supervisor is briefed on the approved method and inspection requirements.

This is QA because competent people and a controlled process reduce the likelihood of defective installation.

QA example 4: Internal audits

An internal audit checks whether material approvals, method statements, ITPs and inspection records are being managed in accordance with the project’s procedures.

The audit is not inspecting one finished wall or one concrete element. It is evaluating whether the management system and its processes are functioning as intended.

That is why quality audits in construction projects are normally considered QA activities.

Quality Control examples

QC example 1: Reinforcement inspection

Before a concrete pour, the engineer or inspector checks:

Bar sizes
Spacing
Laps
Cover
Starter bars
Openings
Embedments
Cleanliness

The check confirms whether the installed reinforcement complies with the approved drawings and specification.

This is Quality Control.

QC example 2: Concrete testing

During the concrete pour, the team checks the delivery ticket, performs the required workability test, records the concrete temperature and prepares test specimens.

These are QC activities because the actual concrete is being checked against specified requirements.

QC example 3: Material delivery inspection

A delivery arrives on site. The engineer checks the product, quantity, markings, condition and certificates against the approved material submittal.

This is QC because the delivered material is being verified before it is accepted for use.

QC example 4: Final inspection

Before an area is handed over, the project team inspects the completed work and records any incomplete, damaged or unacceptable items.

This is also Quality Control, although leaving all QC until the final inspection would obviously be a very bad approach.

QA vs QC in construction

Quality Assurance and Quality Control are both essential parts of construction quality management.

Construction is not a controlled production line. Every project has a different client, design team, supply chain, workforce, location and set of contractual requirements.

The product is built outdoors or within a changing site environment. Work completed by one subcontractor is often covered or affected by the work of another. Designs may continue to develop while construction is already in progress.

This makes the relationship between QA and QC particularly important.

Project stage	Quality Assurance activity	Quality Control activity
Preconstruction	Quality Plan, procedures and responsibilities	Review of samples and technical submissions
Procurement	Supplier evaluation and specification of requirements	Delivery inspection and certificate checks
Before an activity	Approved method statement, ITP and competent personnel	Readiness and pre-start inspection
During construction	Defined process, supervision and controlled information	Inspection, measurement and testing
Completion	Handover procedure and records requirements	Final inspection, testing and snagging
Improvement	Audits, trend analysis and corrective action	NCR, defect and test-result data

QA and QC should therefore operate as one connected system.

QA establishes what needs to happen. QC provides evidence of what actually happened.

How Quality Assurance and Quality Control work together

Let’s use a concrete pour as a practical example.

Quality Assurance before the concrete pour

The QA arrangements may include:

Reviewing the drawings and specification
Approving the concrete mix design
Evaluating the concrete supplier
Preparing the method statement
Preparing the Inspection and Test Plan
Defining hold and witness points
Identifying the required tests
Confirming acceptance criteria
Assigning responsibilities
Checking that testing equipment is calibrated
Briefing the construction team

Quality Control before and during the concrete pour

The QC activities may include:

Inspecting reinforcement
Inspecting formwork
Checking dimensions and levels
Checking embedded items
Reviewing concrete delivery tickets
Checking workability
Recording concrete temperature
Preparing test specimens
Monitoring placement and compaction
Checking curing arrangements

What happens if QC identifies a problem?

Imagine that several concrete test results fail to meet the specified strength.

QC has identified the problem, but QC alone should not be the end of the process.

The project team may need to:

Control the affected concrete
Raise a nonconformance
Assess the structural implications
Carry out additional testing
Determine the appropriate correction
Investigate the root cause
Review the supplier
Change the mix, process or supervision
Verify whether the corrective action was effective

The information discovered through QC has now been fed back into QA.

This is how the two functions should work together: QC identifies what happened, while QA improves the system to reduce the likelihood of it happening again.

Is an ITP Quality Assurance or Quality Control?

An Inspection and Test Plan can be part of both QA and QC.

Creating, reviewing and approving the ITP is mainly a QA activity. The team is planning what needs to be inspected, who will inspect it, what criteria apply and which records must be produced.

Carrying out the inspections and tests listed in the ITP is QC.

For example:

Defining a reinforcement hold point in the ITP is QA.
Inspecting the reinforcement at that hold point is QC.
Defining the required concrete tests is QA.
Performing and recording those tests is QC.

This is why it is not always sensible to force every quality activity into one category. Some tools connect planning, execution and verification.

Is an audit Quality Assurance or Quality Control?

An audit is generally considered a Quality Assurance activity.

An audit evaluates whether the management system and its processes are suitable, implemented and effective.

It may check whether:

Responsibilities are clear
Approved procedures are being followed
Current documents are available
Inspections are being completed
Records are being retained
Nonconformities are being controlled
Corrective actions are effective

An audit may review QC records, but that does not make the audit itself a QC inspection.

The distinction is simple:

An inspection asks: “Does this work comply?”
An audit asks: “Is the system for controlling this work functioning properly?”

Is an NCR Quality Assurance or Quality Control?

Identifying a nonconformance during an inspection is normally a QC activity.

For example, an inspector discovers that installed reinforcement does not match the approved drawing. The problem is recorded in a Non-Conformance Report.

However, the complete NCR process extends beyond QC.

Containment, correction, root-cause analysis, corrective action and effectiveness review connect the NCR back to the wider QA system.

If the project simply repairs the reinforcement but does not investigate why the wrong detail was installed, the immediate defect may be corrected while the underlying process remains unchanged.

That is how the same type of NCR appears again a few weeks later.

Is document control QA or QC?

Document control is mainly a QA process because it establishes how documents are reviewed, approved, revised, distributed and retained.

The purpose is to prevent people from working with incorrect or obsolete information.

However, checking that the latest approved drawing is actually being used at the workface can also be treated as a QC verification.

A document control procedure may be perfect on paper, but somebody still needs to verify that the correct revisions have reached engineers, supervisors and subcontractors.

You can read more about this in the complete guide to construction document control.

Is testing Quality Assurance or Quality Control?

Performing a test on a material, product or completed element is normally QC.

Examples include:

Concrete strength testing
Soil compaction testing
Weld testing
Pressure testing
Electrical testing
Water-tightness testing
Functional testing

Planning the test, defining its frequency, selecting the laboratory, approving the method and confirming the acceptance criteria are QA activities.

Again, planning and verification work together.

Who is responsible for QA and QC?

Many construction projects have a QA/QC department, a Quality Manager, QA/QC engineers and inspectors.

This sometimes creates the impression that quality is the responsibility of the Quality Department.

It is not.

The Quality Department may establish, coordinate, monitor and verify the quality system, but it does not physically produce most of the work.

Typical responsibilities include:

Senior management

Establishing the organisation’s quality direction
Providing sufficient resources
Defining responsibilities and authority
Reviewing performance
Supporting improvement

Project manager

Implementing the project’s quality arrangements
Coordinating different departments
Ensuring that programme and commercial pressure do not bypass required controls

Quality manager

Developing and monitoring the Quality Management System
Coordinating audits
Reviewing performance and trends
Supporting corrective action
Reporting quality issues to management

QA/QC engineer or inspector

Reviewing inspection documentation
Coordinating inspections and tests
Verifying compliance
Maintaining quality records
Reporting nonconforming work

Construction engineers and supervisors

Planning and supervising the work
Using approved documents
Checking readiness before requesting inspection
Correcting issues identified during the work

Subcontractors and operatives

Understanding the requirements
Following approved methods
Completing the work correctly
Reporting problems rather than hiding them

The quality team cannot inspect quality into work that has been poorly planned, badly managed or incorrectly executed.

Common misunderstandings about QA and QC

“QA is just paperwork”

Bad QA can certainly become paperwork.

Good QA creates practical arrangements that help people understand requirements, responsibilities, risks and controls.

A short procedure that reflects reality is more valuable than a 100-page manual that nobody follows.

“QC happens only at the end”

QC should take place throughout the work.

In construction, many elements become inaccessible. Inspection points need to be planned before work is covered or progresses to the next stage.

“The quality inspector is responsible for quality”

The inspector verifies work but does not normally control every activity, manage every subcontractor or produce the finished product.

Quality remains a shared responsibility.

“If we have QA, defects should never happen”

No system can guarantee that no defect will ever occur.

The objective is to reduce the risk, detect problems early, control their consequences and learn from them.

“QC fixes quality problems”

QC identifies and records problems. The construction team, designers, suppliers and management may all be involved in determining and implementing the solution.

“QA and QC should be completely separate”

Independence may be important for some inspections, tests and audits. However, QA and QC information must still be connected.

If QC findings are not analysed and used to improve QA processes, the organisation loses one of its best sources of improvement data.

How ISO 9001 relates to QA and QC

ISO 9001 provides a framework for establishing and improving a Quality Management System.

It does not divide every requirement neatly into a QA box or a QC box.

Its requirements address areas such as:

Leadership
Planning
Competence
Documented information
Operational control
Monitoring and measurement
Internal audits
Management review
Nonconformity
Corrective action
Continual improvement

Some of these activities are traditionally associated with QA, while inspections, testing and product acceptance are more closely associated with QC.

However, the standard is ultimately concerned with whether the complete management system enables the organisation to meet requirements consistently and improve its performance.

How to improve QA and QC in a construction project

1. Keep the system practical

Do not create procedures simply because another company has them.

Define controls that reflect the project’s risks, contractual requirements, complexity and available resources.

2. Plan inspections before work starts

Do not prepare the ITP after construction has already begun.

Inspection points, responsibilities, acceptance criteria and records should be agreed before the activity starts.

3. Make requirements easy to find

Engineers and supervisors should be able to identify the approved drawing, specification, method statement, ITP and material submission without searching through several systems or email chains.

4. Involve construction teams

Quality procedures should not be developed only by the Quality Department.

The people who plan, supervise and execute the work should contribute to the arrangements they are expected to follow.

5. Use quality data properly

Record and monitor recurring NCRs, failed inspections, test failures, overdue approvals and rework.

Useful construction quality metrics and KPIs should help management understand where the system needs attention.

6. Brief people in simple language

Short inductions and quality toolbox talks can be more effective than expecting every operative to read a long procedure.

7. Feed QC results back into QA

If the same type of defect continues to appear, do not simply raise more NCRs.

Review the process, training, supplier, design information, supervision and inspection arrangements that allowed the problem to happen repeatedly.

Frequently asked questions

What is the main difference between Quality Assurance and Quality Control?

Quality Assurance focuses mainly on preventing problems by establishing effective processes and controls. Quality Control focuses mainly on checking products, services or completed work to determine whether requirements have been met.

Which comes first, QA or QC?

QA planning normally begins first because the organisation needs to define requirements, responsibilities and controls before work starts. QC then verifies the work as it is produced. However, both continue throughout the lifecycle, and QC results should be used to improve QA.

Is QA proactive and QC reactive?

QA is generally proactive and preventive, while QC is generally detective. However, QC does not need to be purely reactive. A well-timed inspection can identify a problem early enough to prevent it from affecting later work.

Is inspection QA or QC?

Performing an inspection on a product, material or construction activity is normally QC. Planning the inspection process, defining its frequency and establishing its acceptance criteria are QA activities.

Is testing QA or QC?

Performing the test is normally QC. Planning which tests are required, approving the test method, selecting a competent laboratory and defining acceptance criteria are QA.

Is an ITP QA or QC?

Preparing and approving an Inspection and Test Plan is mainly QA. Carrying out and recording the inspections and tests identified within it is QC.

Is an audit QA or QC?

An audit is generally a QA activity because it evaluates whether the management system and its processes are suitable, implemented and effective.

Is an NCR QA or QC?

Identifying and recording a nonconformance is normally connected to QC. Root-cause analysis, corrective action and improvement of the process connect the NCR back to QA.

Can the same person perform QA and QC?

On smaller projects, the same person may carry out both types of activity. The important issue is whether responsibilities, competence and any necessary independence are clearly defined. Certain inspections, tests or audits may require independent verification.

What does QA/QC mean in construction?

QA/QC in construction describes the combined system used to plan how quality will be achieved and verify whether the completed work meets drawings, specifications, contractual requirements, codes and approved submissions.

Final thoughts

Quality Assurance and Quality Control are different, but they should never operate as separate worlds.

QA establishes the processes, responsibilities and controls intended to prevent quality problems.

QC inspects, measures and tests the actual result to identify whether those controls have produced compliant work.

The information collected through QC should then be used to improve QA.

If inspections repeatedly identify the same problem, the answer is not simply to carry out more inspections. The project should understand why the process continues to produce the problem and make the necessary changes.

At the same time, a project should not assume that plans, procedures and audits automatically guarantee quality. The actual work still needs to be inspected and tested at the correct stages.

To put it simply:

QA helps us do the right things in the right way.
QC confirms whether the result is actually right.

Both are necessary, both should remain practical and both need the involvement of the entire project team—not just the people with “Quality” in their job title.

Related construction quality guides

Build a practical construction quality system

Need an editable Inspection and Test Plan? Download the Free ITP Template.

Looking for practical forms for inspections, NCRs, corrective actions, audits, RFIs and quality reporting? View the 12 Essential Quality Documents Pack.

You can also browse all available construction quality templates.