Cold-formed structural sheet steel is everywhere in commercial construction — metal building frames, steel joist connections, bridging welds, decking attachments. Yet most fab shops focus their WPS library on AWS D1.1 and never develop a compliant D1.3 procedure. That is a real audit gap. This article covers what AWS D1.3 actually requires, how to write a conforming WPS, and where it diverges from D1.1.
What AWS D1.3 Covers
AWS D1.3, Structural Welding Code—Sheet Steel, applies to arc welding of cold-formed structural members where the base metal thickness is up to 3/16 in (4.8 mm). The code addresses the specific challenges of welding thin material: burn-through risk, small fusion zones, and joint geometries that do not appear in structural plate work — particularly the flare-groove joints produced by cold-formed radii.
The code does NOT cover welding of hot-rolled sections (those fall under D1.1), reinforcing steel, or pressure applications. It is also distinct from AWS D1.6 (stainless) and D1.2 (aluminum). If you weld cold-formed steel joists to a W-shape beam, the joist connections follow D1.3 while any work on the beam itself follows D1.1. That means you may need both codes active on the same job, with separate WPS documents for each.
Base Metals and Filler Metal Selection
AWS D1.3 recognizes cold-formed sheet steel made from a range of ASTM specifications including A1003, A653, A792, A1008, and similar grades. The material must have minimum yield strength and weldability characteristics consistent with the code's requirements.
Filler metal selection under D1.3 differs meaningfully from D1.1. The code allows electrodes classified to AWS A5.1 and A5.20, but steers practitioners toward electrodes suited for thin material where heat input must be tightly controlled. E6013 and E7014 electrodes — which are rarely the preferred choice for structural plate — often outperform E7018 on thin sheet because their coating chemistry produces shallower penetration and reduces burn-through risk. E7018 deposits more aggressively and can simply blow through light gauge material when the operator or parametric setup is not dialed in.
Your WPS must document the exact electrode classification and must not allow arbitrary switching to a different AWS A5 classification or F-Number group without requalification.
Prequalified Joints in AWS D1.3
The prequalified joint details in D1.3 look different from the groove and fillet families in D1.1 Annex B. The most common prequalified configurations are:
Fillet welds on lap joints. Lap joints are the workhorse of sheet steel fabrication. D1.3 gives minimum fillet weld sizes relative to the thinner sheet thickness. A minimum single-pass fillet is often required to ensure adequate fusion through the full sheet cross-section.
Flare-groove welds. A flare-bevel groove is formed when a flat plate meets a curved, cold-formed surface. A flare-V groove is formed between two curved surfaces. Because the radius is inherent to the cold-formed geometry, effective throat calculation for these joints is different from standard groove welds. AWS D1.3 provides an effective throat factor based on the radius of the formed section. Do not substitute D1.1's throat rules — the geometry and the math are different.
Square-groove butt welds. For very thin material in a butt configuration, square-groove joints are prequalified with specific root opening limits that prevent bridging of the weld pool over an unfused gap.
To use a prequalified joint, your WPS must match the joint detail exactly: root opening, included angle where applicable, backing provisions, and fit-up tolerance limits. Any deviation requires procedure qualification testing.
Qualification Testing: What D1.3 Requires vs D1.1
When a prequalified joint cannot be used, AWS D1.3 provides a procedure qualification path. Test requirements include:
- Macro-etch cross sections to verify fusion, effective throat, and absence of sharp notches in the weld root.
- Fillet weld break tests to confirm weld strength relative to the base metal.
- Visual examination per the code's acceptance criteria.
Tensile and bend tests are generally not required for D1.3 qualification in the way they are required for D1.1 PQR testing. The macro-etch and break test are the primary mechanical verification method. Auditors from a structural steel background sometimes arrive at a sheet steel shop expecting bend coupons and become suspicious when none exist. The code does not require them; point the auditor to the D1.3 qualification section, not D1.1.
WPS Content Requirements
The WPS for D1.3 work must address the same general categories as any AWS welding procedure:
- Process and mode of metal transfer
- Base metal specification, grade, and thickness range
- Filler metal classification, trade name, and diameter
- Current type and polarity
- Amperage and voltage ranges
- Travel speed range
- Joint configuration and backing provisions
- Preheat and maximum interpass temperature
- Number of passes and pass sequence (single-pass limits apply to many D1.3 joints)
That last item carries extra weight for thin gauge. Many D1.3 fillet welds must be made in a single pass. Multi-pass is permitted only where joint geometry and thickness allow adequate heat management. Document this constraint explicitly. If the WPS says "single pass required" and production welds show visible restart marks or variable bead profile suggesting multiple passes, the inspector has a legitimate finding.
Preheat for Sheet Steel
Preheat requirements for cold-formed sheet steel are generally lower than for structural plate, reflecting the lower carbon content of most cold-formed grades. However, distortion and burn-through risk increase at elevated temperatures, making interpass temperature control just as critical as minimum preheat. See Preheat and Interpass Temperature on a WPS for documentation practices that satisfy both D1.1 and D1.3 audits, including how to record contact pyrometer readings.
In cold weather conditions, even thin sheet steel may need preheat to remove moisture from the surface and avoid porosity. D1.3 has specific provisions for this. See Cold Weather Welding Requirements under AWS D1.1 — while that article focuses on D1.1, the moisture-driven porosity mechanism is the same for any thin structural steel application.
Common Audit Findings for D1.3
Third-party auditors reviewing sheet steel fabrication routinely cite:
Missing D1.3 WPS. A shop presents a D1.1 WPS for work on cold-formed members. The D1.1 WPS may be excellent in other respects, but the code requires D1.3 compliance and the auditor must flag the non-conformance regardless.
Incorrect effective throat calculation for flare-groove welds. Shops apply standard groove weld throat geometry to a flare-V joint, overstating the effective throat and the weld's calculated load capacity. This shows up in connection design checks and in the structural engineer's review.
Single-pass rule violations. Multi-pass fillets applied where the WPS or prequalified joint detail requires a single pass. This is harder to catch during in-process inspection than to prevent with a clear, unambiguous WPS.
No base metal traceability for light gauge material. Mill certificate review — confirming the sheet steel meets the referenced ASTM specification — is often absent for light gauge material where it is considered routine commodity. See Mill Certificate Review for WPS Base Metal for why this matters even for thin plate.
Stacking D1.3 and D1.1 on the Same Job
Metal building construction commonly requires both codes. The general rule is that each weld procedure complies with the code applicable to the thinner or cold-formed member involved. Connections between a hot-rolled beam and a cold-formed purlin require a D1.3 WPS for the purlin-side fillet welds and a separate D1.1 WPS for any groove weld on the structural member itself. Maintain separate WPS documents — do not combine them into a single procedure that vaguely references both codes without specifying which provisions govern which welds.
Rule library based on AWS D1.1:2025; verify against your governing edition.
Getting Your D1.3 Library Audit-Ready
If your shop works on metal buildings, steel deck connections, or any light gauge structural application, a D1.3 WPS library is not optional — it is a code requirement. A two- to three-procedure library covering fillet welds on lap joints and the most common flare-groove configurations will cover the majority of sheet steel work. If your current WPS software does not support D1.3 document generation alongside D1.1, see what purpose-built welding procedure software offers versus spreadsheet approaches at /pricing.