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 Clause 5. 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.