AWS D1.1 Scope and Exclusions: When You Don't Need a D1.1 WPS
AWS D1.1:2025 does not cover all structural welds. Learn which materials, thicknesses, and applications fall outside D1.1 scope and which code applies instead.
One of the most common compliance gaps in structural fabrication is applying the wrong welding code—or applying D1.1 where it does not belong, while missing the code that actually governs the work. AWS D1.1:2025 has a precisely defined scope, and understanding its limits is as important as knowing what it requires.
This article walks through the scope boundaries of AWS D1.1:2025, identifies the most common exclusions, and names the applicable code for each situation. Getting this right before the first arc strikes prevents rework, audit findings, and—in the worst case—nonconforming structure that an inspector cannot accept.
The Core AWS D1.1 Scope Statement
AWS D1.1:2025 applies to the welding of carbon and low-alloy structural steels with a minimum specified yield strength of 100 ksi or less, in thicknesses of 3/16 in (5 mm) and greater, in structures subject to static and cyclic loading. The standard addresses groove welds, fillet welds, plug and slot welds, and stud welding on these materials.
This one paragraph eliminates a substantial number of welding applications from D1.1 coverage.
Thickness Limit: Sheet Steel Under 3/16 Inch
AWS D1.1 does not apply to material thinner than 3/16 in. For cold-formed sheet steel—deck, light-gauge framing, cladding, and similar products—the governing standard is AWS D1.3 (Structural Welding Code—Sheet Steel).
D1.3 uses arc spot welds (puddle welds), arc seam welds, and arc plug welds through thin sheets, with qualification methods that account for the small material volumes involved. The arc spot weld qualification test in D1.3 is a wash test, not the bend-and-break test used in D1.1 fillet weld qualification.
A fabricator who qualifies welders under D1.1 alone cannot certify them for D1.3 work without separate D1.3 qualification. The two codes are not interchangeable for welder performance qualification even though the physical welder may be the same person.
Material Type: Stainless Steel
AWS D1.1 applies only to carbon and low-alloy steels. Stainless steel structural welding—including austenitic, ferritic, duplex, and martensitic grades used in structural applications—falls under AWS D1.6 (Structural Welding Code—Stainless Steel).
D1.6 has different essential variables for WPS qualification, different preheat requirements (generally none for austenitic grades, controlled for duplex), and different joint geometry provisions. The most common confusion arises on mixed assemblies: a carbon steel support structure for stainless equipment. The carbon steel frame uses D1.1 WPSs; the stainless vessel or component uses D1.6 WPSs. The transition joint—where stainless attaches to carbon steel—requires careful WPS selection, often with austenitic or high-nickel filler metal, and a WPS qualified under D1.6 or D1.1 as appropriate to which side governs.
Welding of reinforcing bar (rebar) is governed by AWS D1.4 (Structural Welding Code—Reinforcing Steel), not D1.1. This distinction matters frequently in structural work where embedded plates, embed angles, or weld studs connect to rebar in concrete.
A common D1.4 application is a weld plate embedded in a concrete wall with headed studs on one side (D1.1 Clause 7 for stud welding) and rebar lap-welded to anchor bars on the other side (D1.4). The CWI must hold separate qualifications under both codes to inspect both weld types on the same connection. The rebar to structural plate weld procedure article covers how to handle the dual-code connection.
Pressure Piping and Pressure Vessels
AWS D1.1 does not apply to pressure piping or pressure vessels, regardless of whether the piping is routed through or supported by structural steel. Pressure equipment is governed by:
ASME B31.1 (Power Piping)
ASME B31.3 (Process Piping)
ASME B31.9 (Building Services Piping)
ASME Section VIII (Pressure Vessels) + ASME Section IX (WPS/PQR qualification)
The WPS qualification records under ASME Section IX look similar to AWS D1.1 PQRs but use different F-numbers, A-numbers, and essential variables. ASME WPSs cannot be substituted for D1.1 WPSs on structural steel, and vice versa—the codes are not equivalent. Shops that do both structural and pressure work must maintain clearly separated WPS libraries to prevent cross-application.
Cold-Formed Steel Members in Pre-Engineered and Light Framing
Pre-engineered metal buildings (PEMBs) often use cold-formed purlins, girts, and secondary members alongside hot-rolled primary frames. The hot-rolled primary frames fall under D1.1; the cold-formed secondary members, depending on their thickness, may fall under D1.3 or under light-gauge framing standards (AISI S100 series). Some PEMB manufacturers have their own proprietary welding specifications approved by the AHJ.
The key question for the fabricator is: what does the governing contract specification call for? If it invokes AWS D1.1 specifically, D1.1 applies to all structural welds meeting its scope. If it invokes AISC 360 and the members in question are AISC-defined structural steel shapes, D1.1 is likely the right code. If the connection is to sheet-metal components, D1.3 may govern that portion.
Tubular Structures for Offshore and Marine Applications
AWS D1.1 covers welded tubular (hollow structural section) connections for onshore structural steel. However, offshore jacket structures, production platforms, and floating structures typically invoke API RP 2A (Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms), which references AWS D1.1 selectively but adds additional requirements for cathodic protection zones, underwater inspection, and high-strength steel tubulars.
For structural steel buildings with exposed tube-to-tube connections under seismic provisions, AWS D1.1 and AISC 341 (Seismic Provisions) govern. For marine or offshore applications, confirm whether the governing specification is AWS D1.1 alone, API RP 2A, or a combination before writing the WPS submittal.
High-Strength Steel Above 100 ksi Yield
AWS D1.1:2025 scope is limited to steels with minimum specified yield strength of 100 ksi or less. Ultra-high-strength steels above that threshold (certain grades of A514/A517 fall just within the limit; some advanced high-strength steels used in special applications exceed it) fall outside D1.1 scope.
Note: A514 and A517 quenched-and-tempered steels have a minimum yield of 100 ksi, which puts them at the edge of D1.1's scope. They are not in Table 5.6 (not prequalified) and must be qualified by test per the tested WPS path. The rule is that A514 and similar Q&T steels require a PQR—they are not covered by prequalified WPS provisions.
For steels above 100 ksi yield, consult the material supplier's welding guidelines and the applicable design specification to identify the governing welding standard.
When the AHJ Specifies a Different or Older Edition
Even when D1.1 is technically the right code, the authority having jurisdiction (AHJ) or the contract may specify an older edition. A project may invoke AWS D1.1:2020 by contract even though AWS D1.1:2025 has since been published. In that case, the 2020 edition governs—including 2020-era table numbers, essential variable lists, and prequalified joint details—regardless of what the fabricator uses internally.
Always confirm the specified edition before writing WPS documents. If the EOR specifies "current edition," verify whether that means the edition current when the project specification was written or the edition current at the time of fabrication. This ambiguity is worth clarifying in writing at project kickoff.
Bridge Welding
AWS D1.5 (Bridge Welding Code) governs welded steel highway bridges, not D1.1. For bridges designed to AASHTO LRFD specifications, D1.5 is the controlling code. D1.5 is significantly more restrictive than D1.1 in several areas: CVN toughness requirements, welding process restrictions, and NDE methods. Applying D1.1 to a highway bridge job is a code violation even though the material, process, and techniques may appear similar.
Putting It Together: Code Selection Flowchart
When a new project arrives, the first question before writing a WPS is: what code governs? Work through these questions:
Is the material structural carbon/low-alloy steel ≥ 3/16 in? → If yes, D1.1 is the starting point. If no, go to D1.3 (sheet), D1.6 (stainless), or D1.4 (rebar).
Is it a highway bridge? → D1.5.
Is it pressure piping or a pressure vessel? → ASME B31.x or ASME Section VIII + IX.
Does the contract specify a code? → That code governs, even if you would otherwise select differently.
Does the AHJ impose an edition? → Confirm the specific edition, not just the code designation.
For multi-code projects, maintain separate WPS binders by code. Intermingling D1.1 and ASME WPS records is a persistent audit failure. For more on managing WPS programs across multiple code requirements, see multi-code WPS management for AWS D1.1, ASME IX, and API 1104.
Understanding the scope boundary prevents the significant liability of using the wrong qualification base for a production weld. When scope is ambiguous—a common situation on mixed-occupancy buildings with both structural steel and mechanical systems—put the question to the EOR in writing before work begins. For a welding procedure management system built around AWS D1.1:2025 scope and qualification rules, see wpswelding.com/pricing.
Rule library based on AWS D1.1:2025; verify against your governing edition.
FAQ
Frequently asked.
Does AWS D1.1 apply to sheet steel thinner than 3/16 inch?
No. AWS D1.1:2025 applies to structural steel 3/16 in (5 mm) and thicker. Sheet steel below that threshold falls under AWS D1.3 (Structural Welding Code—Sheet Steel), which uses different qualification methods and acceptance criteria.
If a pressure vessel is built on a structural steel base frame, does the base frame weld need a D1.1 WPS?
Only the structural frame itself is governed by D1.1 if the governing specification invokes it. The pressure vessel shell and nozzles are governed by ASME Section VIII, which requires qualification per ASME Section IX—a separate WPS. The two sets of WPS must be maintained distinctly and not interchanged.
Does AWS D1.1 apply to stainless steel structural members?
No. Stainless steel structural welding falls under AWS D1.6 (Structural Welding Code—Stainless Steel). D1.1 is limited to carbon and low-alloy steels. A shop doing stainless structural work must qualify WPSs under D1.6 and train their CWIs on the differences.
What code covers rebar-to-structural-plate welds?
Reinforcing steel welding is governed by AWS D1.4 (Structural Welding Code—Reinforcing Steel). When the detail is a rebar welded to a structural plate, both D1.4 and D1.1 may apply to different elements of the connection. The EOR's drawings and specification should designate the governing code for each weld type in the detail.