Does each modular fabricator need their own AWS D1.1 WPS, or can they share one?

Each fabricator must have WPS documents that reference their own Procedure Qualification Records (PQRs) or that are qualified as prequalified per AWS D1.1 Clause 5 with their shop's specific parameters. A WPS issued by the general contractor or EOR does not transfer qualification — the fabricator performing the welds owns the qualification responsibility. Sharing a single PQR between shops is only possible if both shops witness or jointly conduct the qualification test, which is uncommon.

Who is responsible for WPS compliance when a general contractor uses multiple modular sub-fabricators?

The general contractor is responsible for ensuring that each sub-fabricator has qualified WPS documentation covering their scope of work. The GC's quality plan should require WPS submittals from each fabricator before production welding begins, and the GC's CWI or third-party inspector should verify WPS coverage at each shop. AWS D1.1 responsibility flows to whoever is performing the welds.

What WPS is required for the field connections between modules?

Field connections between modules are typically the highest-consequence welds in a modular project — they're made in the field, often in challenging positions, and they must develop the full structural capacity of the joint. A separate WPS covering the field connection joint configuration, position, and process is required. If the field connection is a different joint type (CJP groove vs. fillet) or process (SMAW in the field vs. FCAW in the shop) from the shop WPS, it must be qualified separately.

How do I track welder qualification continuity across multiple shifts at multiple modular fab shops?

Each fabricator maintains their own welder performance qualification (WPQ) records. The general contractor's quality plan should require certified copies of current WPQ records for all welders, with the 6-month continuity rule per AWS D1.1 Clause 6.4.1 enforced at the individual fabricator level. A welder qualified at Shop A does not automatically carry that qualification to Shop B — the new employer must accept or re-test the welder per their own qualification program.

WPS Management for Modular and Skid-Mounted Structural Assemblies

How to manage welding procedure specifications across multiple fabricators building modular structural assemblies, including traceability, AISC certification, and field connection WPS requirements.

Modular construction — where structural assemblies are fabricated off-site, transported, and connected in the field — concentrates most welding in the shop environment, where quality control is easier to manage. But when multiple fabricators are involved, or when the field connection welds are structurally critical, WPS management across the program becomes the CWI's primary administrative challenge.

The Multi-Fabricator Problem

A typical modular structural project might involve a primary steel fabricator building the main frames, a secondary shop doing stair towers and mezzanines, and field crews making the module-to-module connections. Each of these parties is welding to AWS D1.1, but their WPS libraries, PQR records, and welder qualifications are separate and independent.

AWS D1.1 assigns qualification responsibility to the organization performing the welds. There is no provision for one fabricator's PQR to cover another fabricator's production welding unless both organizations are party to the same qualification test and sign off on the same PQR document. In practice, this means the general contractor must:

Require WPS submittals from each fabricator before production welding begins.
Verify that each WPS covers the joint types, base metals, processes, and thickness ranges in that fabricator's scope.
Retain copies of each PQR (or confirmation of prequalified status) for the project quality file.
Confirm that each fabricator has a qualified CWI or inspection plan in place for their own work.

The GC's quality manager should maintain a WPS coverage matrix: columns for each joint type in the project, rows for each fabricator, with cells showing the WPS number that covers each combination. Any gaps are found during submittal review, not during production.

AISC Fabricator Certification in Modular Programs

AISC fabricator certification (Standard, Sophisticated Paint, or other categories) applies at the shop level. A shop certified for AISC Category CPF (Complex painted) has demonstrated the QC capability for that certification level — but only for work performed in that certified facility.

For modular projects subject to AISC 303 or project-specified AISC certification requirements:

Each fabricator performing structural steel work must hold the applicable AISC certification for their scope. A non-certified sub-fabricator handling secondary structural members on a project that requires AISC-certified fabrication is a nonconformance.
The field crew performing module-to-module connection welds may not be a certified steel erector. Verify whether the project specification includes AISC erector certification requirements (AISC Category E) for the field connection team.

When verifying AISC certifications, check the AISC online registry for current status — certifications lapse if annual audits are not completed.

WPS for Shop vs. Field Work: Different Challenges

Shop welding in modular construction benefits from consistent positioning (often positioner-assisted), controlled temperature and humidity, and immediate NDE access. Field connections sacrifice most of these advantages.

A common mistake is writing the field connection WPS to match the shop procedure: same wire diameter, same current range, same position. A shop FCAW-G procedure at 200+ amps in the flat/horizontal position cannot be directly transferred to a field crew welding overhead in tight quarters between set modules.

Your field connection WPS should independently qualify for:

All positions required — if the field connection groove weld will be made in 3G (vertical) or 4G (overhead) positions, the PQR must include those positions. A PQR tested only in 1G (flat) qualifies flat and horizontal only under AWS D1.1 qualification rules.
The actual process — field crews frequently use SMAW (stick) for connection welds because of its tolerance for wind, position, and lack of wire feed equipment. If the shop WPS is FCAW-G and the field WPS is SMAW, those are separate qualifications.
The joint geometry as it will actually be fit up — module-to-module connections often have tighter dimensional tolerances than shop-built joints because each module's cumulative dimensional tolerance leaves less room for fit-up adjustment at the connection. Your WPS should note the allowable fit-up tolerances per AWS D1.1 Table 6.1 (prequalified) or the tested range, and the inspection hold points for fit-up verification before welding begins.

Rule library based on AWS D1.1:2025; verify against your governing edition.

Traceability and Weld Map Requirements

In modular construction, the fabricator ships a complete structural assembly — and the owner or EOR may not have the ability to inspect in-place welds once the module is connected. Pre-shipment inspection is the last checkpoint.

Each module should ship with:

A weld map keyed to the erection drawings, showing each weld designation, the WPS number used, the welder ID who performed the weld, and the NDE results (if required).
Certified copies of WPS and PQR documents covering all welds on that module.
NDE reports with accept/reject dispositions for any NDE-required joints.
Welder WPQ certifications (or at minimum a log showing welder IDs, qualification basis, and current continuity status) for all welders who worked on the module.

This pre-shipment documentation package becomes part of the project quality record. If a weld failure is discovered after installation, the weld map and welder ID allow traceability back to the specific WPS, the PQR qualification basis, and the welder's qualification history.

For an example of what a complete weld documentation package includes, see weld traveler and traceability documentation for production welding and minimum documentation for an AWS D1.1 welding program.

Managing Welder Continuity Across Multiple Shops

AWS D1.1 Clause 6.4.1 requires that welders demonstrate continuity of qualification by welding in the relevant process at least once in any 6-month period, or be retested. In a modular program with multiple fabricators, each fabricator tracks their own welders' continuity independently.

The GC's quality plan should require that each fabricator certify welder continuity at the time of WPS submittal and at regular intervals (monthly is practical for long-duration programs). A continuity lapse discovered during production — or worse, after module shipment — requires disposition of all welds made after the lapse date, which may mean NDE review or requalification testing on a production weld sample.

If your organization manages welder qualification tracking across multiple shops, see EPC contractor WPS management for multiple fab shops and welder qualification and WPS traceability for a framework that scales to modular programs.

Pre-Shipment Inspection Strategy

For modular assemblies, the most effective quality checkpoint is a structured pre-shipment inspection — a formal hold point before the module leaves the fabricator's yard. The inspection should verify:

All required NDE has been completed and results documented.
The weld map is complete with no uninspected weld designations.
Dimensional checks confirm the module will connect correctly in the field (connection plates, embed locations, bolt hole patterns).
All WPS and welder qualification documents are in order.
Any open nonconformance reports (NCRs) have been dispositioned and closed.

Schedule this inspection with enough lead time to allow corrective action before the transport window. A module that arrives on-site with open NCRs or missing documentation holds up the erection schedule at the worst possible moment.

For a WPS management tool that handles multi-shop document libraries, welder continuity tracking, and qualification matrix views, see the plan options at our pricing page.