AWS D1.1 defines what you must do. The project specification defines what this particular owner also requires. Those two documents rarely say the same things, and the gap between them is where fabricators lose qualification audits, miss required tests, and get NDE scope rejections from the contractor's QC representative.
Understanding how supplementary owner requirements flow into the WPS, PQR, and QC plan is a practical skill every welding supervisor and CWI needs before a contract kicks off—not during the first pre-inspection meeting.
AWS D1.1 as a Floor, Not a Ceiling
The AWS D1.1 structural welding code establishes minimum requirements for WPS qualification, welder performance qualification, and inspection. Any owner or engineer of record can require more. Section 1 of AWS D1.1 says as much: the code does not limit the owner's authority to specify additional requirements. Those additional requirements are contractually binding even though they are not part of the base code.
Common supplementary requirements fall into four categories: preheat, CVN impact toughness, NDE scope, and documentation. Each has a different implication for the WPS package.
Preheat Above the Code Minimum
AWS D1.1 Table 5.8 gives minimum preheat temperatures for prequalified WPS based on base metal category and thickness. Many structural steel project specifications add a blanket minimum—200 °F for all welding regardless of thickness, for example—or tie the preheat to carbon equivalent using a formula stricter than what D1.1 uses.
When the owner's specified minimum is higher than the Table 5.8 minimum but still within the qualified range of the PQR, this is an inspection requirement only. Add the owner's minimum to the project QC plan and the inspection traveler. The WPS itself may not need revision.
When the owner's minimum falls outside what the PQR demonstrates, or when the PQR was qualified at a preheat lower than what the owner now requires, the WPS must be revised to reflect the higher minimum. Verify that the qualified heat input range and interpass temperature limits are still consistent with the new minimum. See preheat and interpass temperature documentation for how to structure these limits on the WPS form.
CVN Impact Testing When D1.1 Does Not Require It
Under AWS D1.1:2025, CVN impact testing is a supplementary requirement governed by Table 6.8 (Rule library based on AWS D1.1:2025; verify against your governing edition). Table 6.8 is triggered by the project engineer, owner specification, or contract—not automatically by the base code. Many structural steel projects, especially those with seismic loading, cold-service exposure, or fracture-critical members, require Charpy testing even when the base D1.1 provisions do not.
When CVN testing is required and it was not performed on the existing PQR, the PQR must be repeated with Charpy specimens included. There is no shortcut: you cannot retroactively add CVN data to a PQR coupon that has already been destructively tested. This is the most common surprise that catches shops off-guard when a new owner specification arrives for a project type they have not previously worked.
The practical defense is to run CVN specimens on every PQR even when they are not immediately required. The additional cost is modest compared to re-qualifying a WPS mid-project. A PQR that already includes CVN data—test temperature, specimen orientation, absorbed energy values—can support supplementary requirements on future contracts without any retest.
When Table 6.8 is invoked, specific essential variables become essential that are non-essential under the base code. Changes to those variables—such as a change in filler metal F-number classification or a change in base metal group—require requalification of the WPS. See CVN supplementary essential variables under Table 6.8 for the full list of what becomes essential.
NDE Scope Expansions
AWS D1.1 specifies minimum NDE sampling rates for various categories of welds—statically loaded structures allow spot UT on certain connection types while cyclically loaded structures require 100% examination. Owner specifications frequently raise those minimums: 100% UT on all CJP welds, MT on all fillet welds in tension zones, or RT on specific connection types.
The WPS document itself does not change when NDE scope increases. The WPS records process parameters, not inspection frequency. What changes is the QC plan. Your project-specific QC plan must state the NDE scope for each weld category, reference the owner's specification section that requires it, and identify the NDE method, procedure, and acceptance criteria to be used.
NDE sampling rates under AWS D1.1 covers the baseline sampling rates from the code. The QC plan must clearly note where the owner specification supersedes those rates and by how much.
NDE personnel qualifications must match the expanded scope. If the owner requires UT on joint configurations not typically examined at your shop—certain fillet weld geometries, T-joints in heavy plate, or tubular connections—verify that your UT technician's qualification covers those joint types under AWS D1.1 Clause 9 requirements.
Documentation Requirements the Owner May Add
Some specifications require additional documentation that AWS D1.1 does not mandate:
WPS-to-weld traceability. The owner may require that every weld on the project be traceable to a specific WPS number and PQR on the weld map or traveler. AWS D1.1 requires that a qualified WPS govern each weld, but project-level traceability documentation is a contract add-on.
Welder qualification records at setup. Some specifications require that each welder demonstrate a current, qualified WPQ before beginning work on the project, with the QC supervisor verifying the qualification range covers the joints being welded. The WPQ portability rules under AWS D1.1 still apply, but the owner's documentation requirements may be stricter.
Material test report review before welding. Certain owner specs require the CWI to review and accept the mill certificate for each heat of steel used before that steel can be welded. This ties the carbon equivalent, heat number, and material grade on the MTR to the preheat requirements in the WPS.
How to Build These Requirements Into the QC Plan
Before a project begins, review the owner's specification section by section against AWS D1.1 and list every supplementary requirement. For each one, determine:
- Does it require a WPS revision, a PQR supplement, or only a QC plan entry?
- Does it change what is essential in the WPS, potentially requiring requalification?
- Does it add NDE, hardness, or toughness testing that must be performed before welding starts?
Build a project-specific QC plan that documents each supplementary requirement by specification section, states how it will be implemented, and identifies who is responsible for verifying compliance. The weld quality control plan structure under AWS D1.1 article covers the framework for that document.
For projects with multiple WPS covering different base metals, joint types, and processes, flag which WPS each supplementary requirement applies to. A shop welding A36 simple connections under a baseline WPS and A572 Gr. 50 moment connections under a separate CVN-qualified WPS needs to keep the supplementary requirements mapped to the right WPS package.
The CWI's Role in Supplementary Compliance
The CWI is the first line of verification that supplementary requirements are met. Before welding begins on any supplemental scope, the CWI should:
- Confirm the WPS is qualified to the range required by the owner spec.
- Confirm CVN data exists on the PQR if the spec invokes Table 6.8.
- Confirm the project QC plan reflects the expanded NDE scope and acceptance criteria.
- Confirm welders' WPQs cover the joint configurations and positions required.
During welding, verify preheat at each joint before arc strike—not just at the start of the shift. If the owner's preheat minimum is higher than the code table value, use that as the reference. Record the measured preheat on the inspection traveler.
At the closeout package stage, the owner will typically require that all supplementary test records be included in the weld package: CVN test reports, expanded NDE reports, hardness data if required, and MTRs. Start assembling those records early. A missing CVN report found at project closeout is significantly harder to address than one caught at qualification.
For shops with multiple projects running simultaneously under different owner specifications, a WPS library organized by qualification breadth—rather than just by project—helps avoid the situation where a WPS qualifies fine for one project's requirements but lacks CVN data needed for a new contract. The welding procedure library for multi-project AWS D1.1 shops covers how to structure that library. For a cost-effective qualification strategy, start with the pricing page to see how WPS management software can track qualification status across your entire procedure library.