What is the difference between QC and QA under AISC Chapter N?

Quality Control (QC) is the fabricator's internal program — their own inspections, weld records, and process controls. Quality Assurance (QA) is independent verification performed by the special inspector on behalf of the owner or authority having jurisdiction. Both programs must be in place on AISC-certified or code-governed projects, but they are separate activities with separate personnel.

Does the special inspector replace the fabricator's CWI under AISC Chapter N?

No. The fabricator's own QC program — typically run by a CWI on staff — is not eliminated by the special inspector's presence. Both roles operate simultaneously. The fabricator's QC inspector accepts welds by the fabricator's own criteria; the special inspector performs independent verification of that work.

What welding records does AISC Chapter N require fabricators to maintain?

AISC 360 Chapter N requires fabricators to maintain WPS documentation, welder qualification records (WPQ), material certifications (MTRs), and inspection records. For AISC-certified shops, the Steel Construction Manual and AISC 207 Quality Management System provide additional guidance on record format and retention.

When are hold points required in structural welding under AISC Chapter N?

Hold points are defined in the ITP (Inspection and Test Plan). Common mandatory hold points include pre-weld joint fit-up inspection, first-article weld verification before production begins, and post-weld NDE completion sign-off. The EOR or owner may specify additional hold points in the contract documents.

AISC Chapter N: QC and QA for Structural Steel Welding

How AISC 360 Chapter N separates fabricator quality control from special inspector quality assurance, what welding documentation is required, and how to build a program that passes audits.

Structural steel fabrication projects governed by AISC 360 involve two distinct but complementary inspection systems: the fabricator's own quality control program and the owner's quality assurance program performed by the special inspector. Both trace back to AISC 360 Chapter N, and understanding how they divide responsibility is essential for any CWI or QC manager building a compliant welding program.

This article breaks down what each program covers, what documentation is required, how inspection hold points are structured, and how the welding-specific requirements of AWS D1.1:2025 integrate with the AISC framework.

Chapter N in Context

AISC 360 is the Specification for Structural Steel Buildings. Chapter N addresses quality control and quality assurance, establishing the roles, responsibilities, and minimum inspection activities for structural steel fabrication and erection. The IBC adopts AISC 360 by reference, making Chapter N binding on building projects in most jurisdictions.

Chapter N separates responsibilities into two lanes:

Quality Control (QC): The fabricator's program. The fabricator is responsible for controlling their own manufacturing process, inspecting their own work, and maintaining records that demonstrate conformance. This is the "first party" verification.
Quality Assurance (QA): The owner's independent program. The special inspector, hired by or on behalf of the owner, performs QA inspections to verify that the fabricator's QC program is functioning and that the work meets the contract documents. This is the "third party" verification.

Both programs are required. Neither eliminates the need for the other.

The Fabricator's QC Program

A fabricator seeking AISC Certification — the industry benchmark for structural steel quality — must maintain a written QC program. The program is documented in a Quality Management System (QMS) manual, which is audited by the AISC Quality Certification program.

For welding, the fabricator's QC program must address:

WPS library and control: Every weld made in production must have an applicable, written WPS. The WPS must cover the base metal, filler metal, process, position, thickness range, and joint design. WPS documents must be revision-controlled and accessible to welders at the work station.

Welder qualification records (WPQ): Every welder must be qualified under AWS D1.1:2025 or the applicable code. WPQ records must include the test position, process, thickness qualified, electrode/filler used, test date, and the name of the CWI or responsible engineer who witnessed the test. The fabricator's QC program must track active qualifications and flag continuity lapses under AWS D1.1 Clause 6.4.1 — a 6-month rule that voids qualification if the process has not been used. See AWS D1.1 Welder Continuity Six-Month Rule for the specifics.

Material traceability: MTRs (Material Test Reports) for base metals must be matched to the heats used in fabrication. The QC program should specify how heats are tracked from receiving to cut parts to finished assemblies.

In-process and final inspection: The fabricator's CWI performs pre-weld, in-process, and post-weld inspection per AWS D1.1:2025. Records of these inspections — joint fit-up acceptance, visual weld acceptance, NDE results — are maintained by the fabricator and available for QA review.

Nonconformance management: When a weld or dimension falls outside acceptance criteria, the fabricator's program must document the nonconformance, evaluate disposition (accept, repair, reject), and track corrective action. Unclosed NCRs are a common audit finding.

The Special Inspector's QA Program

The special inspector operates under Chapter 17 of the IBC and Chapter N of AISC 360. The special inspector is typically a third-party inspection firm engaged by the owner or the authority having jurisdiction. On larger projects, a special inspection agency coordinates multiple inspectors.

The special inspector for structural steel welding should hold appropriate credentials — typically CWI certification under AWS QC1, or equivalent qualification acceptable to the AHJ. The inspection scope and hold points are defined in the Statement of Special Inspections, which is a project-specific document.

Special inspection activities for structural welding include:

WPS verification: Confirm that applicable, qualifying WPS documents exist before welding begins. The special inspector does not write or approve the WPS but verifies it covers the work being performed.
Welder qualification check: Spot-check that welders performing work are qualified for the process, position, and base metal combination being used. This is a records check, not re-testing.
In-process observation: Observe welding to confirm parameters are within WPS range, preheat is maintained, interpass temperature is controlled, and fit-up was acceptable before the arc started.
NDE witnessing and review: Review NDE reports for completeness and acceptance against AWS D1.1:2025 criteria. The special inspector may witness NDE performance on mandatory hold-point welds.
Final visual acceptance: Independently verify visual acceptance of welds per AWS D1.1:2025 Table 9.13 criteria (or the applicable visual acceptance table).

The special inspector's observations are recorded in Special Inspection Reports, which become part of the project quality file.

Structuring the Inspection and Test Plan

The practical tool that coordinates QC and QA activity is the Inspection and Test Plan (ITP). The ITP is a matrix that lists each inspection activity, the responsible party (fabricator QC, special inspector, or both), the inspection type (review, witness, hold point), and the acceptance criteria or reference standard.

Three inspection types appear on a well-structured welding ITP:

Review (R): The party reviews documentation or completed work records. No mandatory stopping point.
Witness (W): The party is notified and may attend, but production can proceed if they do not show.
Hold (H): Production cannot proceed without sign-off from the designated party. This is a mandatory gate.

Typical welding hold points on structural projects:

Pre-weld joint fit-up and preheat before CJP groove weld root passes
First-article weld review at the start of a new WPS or crew
Post-weld NDE completion and acceptance before the assembly ships or is erected
Final assembly dimensional inspection before turnover to erection

The level of hold-point intensity is negotiated between the fabricator, engineer of record, and owner. More stringent inspection programs are common on seismic-force-resisting systems, demand-critical welds under AWS D1.8, and high-consequence assemblies like moment frame connections.

How AWS D1.1:2025 Integrates with Chapter N

AWS D1.1:2025 is the welding code; AISC Chapter N is the quality framework. They operate together. Chapter N identifies the inspection activities; AWS D1.1 provides the acceptance criteria, parameter limits, and qualification requirements that the inspectors apply.

Key integration points:

AWS D1.1 Table 6.6 defines essential variables — the fabricator's QC program must ensure no essential variable changes occur without requalification.
AWS D1.1:2025 Table 6.8 controls CVN supplementary essential variables — the QC program must log and control heat input on toughness-qualified procedures.
AWS D1.1 visual and NDE acceptance criteria (Clause 9) are the standards against which both QC and QA inspectors evaluate welds.
AWS D1.1 Clause 6.4.1 governs welder continuity — the fabricator's QC program must track this and the special inspector's QA program verifies it spot-check.

For the pre-weld inspection checklist that aligns QC and QA activities at the joint level, see CWI Pre-Weld Inspection Before the Arc Starts. For AISC audit readiness in the full document package, see AISC Certification Audit Readiness for Fab Shops.

Common Gaps That Surface in Audits

AISC auditors and third-party QA reviews routinely find:

WPS that doesn't cover the work: Gaps in the WPS library — a process, position, or base metal combination used in production that no WPS addresses.
Expired or lapsed welder qualifications: WPQ records that don't show the 6-month continuity log, or welders who switched processes without requalification.
NDE reports without weld identification: UT or MT reports that can't be tied to a specific weld joint or assembly because the weld identification system wasn't maintained.
Open NCRs: Nonconformance reports that were written but never dispositionally closed with an engineering or QC sign-off.
ITP not followed: Hold points bypassed because the special inspector wasn't notified or the fabricator's QC inspector missed the sign-off requirement.

A well-run QC program treats Chapter N not as a compliance checkbox but as the framework for systematic quality control that protects both the fabricator and the owner. When the QC and QA programs are functioning correctly, third-party audits and special inspection reviews find few surprises — because the fabricator's own program already caught and documented any issues before the QA layer reviewed them.

For software that manages WPS libraries, welder qualification tracking, and NDE records in one place — built for the AISC audit environment — see WeldingWPS.com pricing.

Rule library based on AWS D1.1:2025. Verify against your governing edition — the AHJ or contract may specify 2020 or an earlier edition.