Every CWI who has been through an AISC certification audit has heard the question: "Show me your QC program." The follow-up is just as predictable: "Who is your QA inspector, and are they independent of production?" If you cannot answer both questions cleanly, you have a gap in your structural welding program — and AWS D1.1 is clear about who does what.
Understanding the distinction between quality control (QC) and quality assurance (QA) is not an academic exercise. It determines who pays for repairs, who has authority to accept or reject a weld, and how your inspection program must be structured to survive a third-party audit.
The Core Distinction
Quality control belongs to the contractor — the fabricator, erector, or welding subcontractor producing the work. QC is internal: the contractor inspects their own work, verifies compliance with the WPS, and resolves non-conformances before the owner's inspector arrives.
Quality assurance belongs to the owner or a designated owner's representative. QA is independent verification that the contractor's QC program is working. The QA inspector audits the product and the process — but does not run the process.
AWS D1.1 Clause 8.1 distinguishes these roles explicitly. The contractor's inspection shall be performed before requesting acceptance by the owner's representative. This is not a formality. A QA inspector who is in the shop catching every defect because the contractor has no functional QC program is a sign the welding program has broken down.
What QC Inspection Covers
The contractor's QC inspector (typically a CWI or CWI-supervised technician) is responsible for:
- Verifying that each welder is qualified per an approved WPS and that their WPQ is current
- Confirming that the applicable WPS is on the floor and that production welding parameters (amperage, voltage, travel speed) fall within the qualified ranges
- Checking fit-up dimensions — root opening, root face, groove angle, and joint geometry — before welding begins
- Monitoring preheat and interpass temperature compliance throughout production
- Performing in-process and final visual inspection of completed welds against AWS D1.1 visual acceptance criteria (Clause 9.25)
- Accepting welds for subsequent NDE or forwarding for owner review
- Documenting non-conformances and verifying corrective action before re-inspection
The QC inspector's authority to accept welds is real and consequential. When a QC inspector stamps a weld "accepted," that record belongs to the contractor's quality file and can be audited years later.
What QA Inspection Covers
The owner's QA inspector — again, a different individual from the contractor's QC inspector — performs independent verification. Their scope typically includes:
- Reviewing the contractor's WPS/PQR/WPQ documentation for completeness and correctness
- Witnessing preheat measurements and fit-up dimensions on selected joints (not all joints)
- Performing or witnessing NDE on a sample or 100% of welds as specified by the contract documents
- Reviewing production weld records and traveler documents for traceability
- Issuing non-conformance reports (NCRs) to the contractor when defects are found
- Releasing work for the next phase (shipping, erection, coating) after acceptance
The QA inspector does not direct the contractor's welders, approve WPSs, or take ownership of the QC program. Their role is verification, not production management.
The AISC Chapter N Framework
AISC 360 Chapter N provides the structural framework that most projects reference. It divides inspection into:
- Fabricator QC — the fabricator's internal inspection, typically under an AISC-certified fabricator's quality manual
- Special Inspection — an independent inspector hired by the owner or the authority having jurisdiction (AHJ), per IBC requirements
- Fabricator QA — a separate role on some large projects where the owner hires their own QA auditor in addition to relying on special inspection
AISC 303 Standard Practice makes a further distinction: the fabricator's quality manual must describe the QC inspection program in writing, including the organization, authority, and qualification of QC personnel. Inspectors reviewing this document during a certification audit will look for evidence that QC is a real, staffed function — not a paper tiger.
AISC N6 specifically addresses welding inspection, requiring that the special inspector verify WPS and welder qualification before production begins, then perform periodic in-process inspection. "Periodic" does not mean random — it means on a frequency sufficient to confirm that the contractor's QC program is functioning.
Who Pays for Repairs?
This is where the QC vs QA distinction has direct financial consequences.
When the contractor's QC inspector rejects a weld, the contractor repairs it. This is normal quality management — catch defects early, before they compound.
When the owner's QA inspector rejects a weld that the contractor's QC had previously accepted, the contractor still repairs it — and typically at their own cost. The fact that QC accepted a defective weld does not transfer liability to the owner; it is a failure of the QC program, not the QA program.
When QA inspection reveals a systemic QC failure — for example, repeated undercut violations that QC should have caught — the owner may have grounds to require enhanced inspection frequencies, or in severe cases, rejection of an entire lot of welds pending investigation.
The Independence Requirement
AWS D1.1 Clause 8.1 is clear: the owner's inspector shall be independent of the contractor's production operations. This means:
- The QA inspector cannot also be the production supervisor or lead welder
- A subcontractor cannot self-certify as both QC inspector and QA inspector on the same contract
- An individual who switches between QC and QA roles on the same project is not in compliance
On smaller projects, the "owner" may be the general contractor, and the "QA inspector" may be an independent testing laboratory (ITL) or special inspection agency hired by the GC. The relationship is the same — independence from production is mandatory.
Practical Takeaways for Fab Shops
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Staff your QC program before production starts. Having a CWI on call for final inspection is not a QC program. QC requires pre-weld, in-process, and post-weld inspection stages, with records at each stage.
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Keep QC records accessible. WPQ logs, preheat records, traveler documents, and NDE reports must be organized and retrievable. When the QA inspector asks for documentation on a specific weld, "we have it somewhere" is not an acceptable answer.
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Do not confuse QA inspection with QC inspection. When the owner's inspector finds a defect, it is too late for QC to have done its job. Use QA findings as a signal that your QC process has a gap — not as a substitute for internal inspection.
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Document your QC program structure. Your quality manual should identify by name (or by role/title) who performs QC inspection, what their qualifications are, and what authority they have to accept or reject work. Auditors look for this.
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Understand the NDE cost question. AWS D1.1 Clause 8.15 states that the contractor pays for initial NDE and repairs; costs for QA-directed testing beyond what the contract specifies may shift depending on findings. Review your contract carefully.
A welding program with strong QC and independent QA is not overhead — it is protection for both the contractor and the owner. Well-maintained inspection records have resolved disputes, avoided litigation, and in some cases provided the documentation trail that demonstrated a failure was caused by service conditions rather than fabrication defects. Build your QC program like someone will audit it. They will.
Rule library based on AWS D1.1:2025; verify against your governing edition — the AHJ or contract may specify an earlier edition.
For more on AISC audit readiness, see Common WPS/PQR Audit Failures Under AISC Certification and AISC Chapter N — QC/QA in a Structural Welding Program. Ready to streamline your WPS documentation? See our pricing.