Structural Welding Code Requirements: AWS D1.1 Field and Shop Welding Rules

Structural welding is code-governed work. Every weld on a building, bridge, or other load-bearing structure must comply with AWS D1.1 (or D1.5 for bridges), and the requirements touch every stage from procedure development through final inspection. Understanding these requirements separates structural welders and fabricators from general welding operations.

The core D1.1 requirements for production welding fall into five categories: qualified procedures, qualified welders, proper fabrication practices, visual and NDE inspection, and documentation. Miss any one and the work doesn’t comply.

WPS Compliance (Clause 5)

Every structural weld must be made in accordance with a written Welding Procedure Specification (WPS). The WPS isn’t a suggestion. It’s a binding instruction document that the welder must follow.

What the WPS Specifies

Prequalified WPSs (Clause 3) use joint designs and parameters listed in the code and don’t require qualification testing. Qualified WPSs (Clause 4) use non-standard parameters and must be supported by a Procedure Qualification Record (PQR). See our AWS D1.1 overview for details on both paths.

Common WPS Violations

• Welding outside the amperage range specified on the WPS
• Using an electrode classification not listed on the WPS
• Ignoring preheat requirements on thick material
• Exceeding interpass temperature limits (typically 600F max for carbon steel)
• Using vertical-down progression when the WPS specifies vertical-up

Welder Qualification (Clause 9)

Every welder performing structural welding under D1.1 must hold a current qualification for the process and position they’re using. Clause 9 defines the qualification tests and their scope.

Minimum Qualification

Most structural shops require 3G + 4G plate qualification as a minimum for new hires. This combination covers all plate positions (flat, horizontal, vertical, overhead) per Table 9.10.

For pipe connections, 6G qualification is needed, which covers all pipe and plate positions.

Continuity Requirement

Welder qualifications don’t expire on a fixed date, but they lapse if the welder doesn’t use a specific process for 6 months. The shop must maintain continuity records showing each welder has used their qualified processes within every 6-month period.

If a qualification lapses, the welder must re-qualify by welding and testing a single coupon, not a full requalification.

Fabrication Requirements (Clause 5)

Clause 5 is the fabrication chapter. It covers the day-to-day rules for making welds.

Base Metal Preparation

• Surfaces within 1 inch of the joint must be clean: no rust, scale, oil, paint, or moisture
• Mill scale may remain if it’s tight and uniform (GMAW, FCAW, SMAW with low-hydrogen electrodes), but heavily scaled surfaces must be cleaned
• Thermally cut surfaces must be ground smooth if the surface roughness exceeds limits

Fit-Up Tolerances

D1.1 specifies tolerances for joint fit-up:

Preheat and Interpass Temperature

Preheat requirements depend on the steel group, thickness, and hydrogen level of the welding consumable:

Measure preheat 3 inches from the joint on the side opposite the heat source. Use temperature-indicating crayons (tempsticks), contact pyrometers, or IR thermometers.

Interpass maximum is typically 600F for carbon steel. Exceeding interpass temperature degrades mechanical properties and can cause cracking in quenched-and-tempered steels.

Arc Strikes

Stray arc marks on base metal outside the weld zone are prohibited. Arc strikes create hard spots (localized martensite) that can initiate cracks, especially in thick or high-strength steels. D1.1 requires arc strikes to be ground smooth and visually inspected.

Weld Profiles

D1.1 Clause 5 specifies acceptable weld profiles:

• Groove welds: Cap must be flush to slightly convex. Reinforcement height limited (1/8 inch max for most thicknesses). No concavity or underfill below the base metal surface
• Fillet welds: Convex or flat profile acceptable. Concavity limited. Convexity must not exceed specified limits (see Figure 5.4)
• Overlap (cold lap): Not acceptable. The weld must fuse smoothly into the base metal at the toes

Weld Repair Procedures

When a weld is rejected, D1.1 Clause 5 governs the repair:

• Remove the defective area by grinding, air arc gouging, or mechanical removal
• The excavation must remove the entire defect
• Inspect the prepared surface (VT, MT, or PT) before re-welding
• Re-weld following a qualified WPS
• Re-inspect the repaired area using the same method that found the original defect

Inspection Requirements (Clause 6)

Visual Inspection (VT)

VT is required on 100% of all production welds. The inspector checks every weld before any additional NDE is performed.

Before welding (fit-up inspection):

• Joint geometry matches the WPS and drawings
• Preheat temperature is correct
• Material is clean
• Welder qualification is current for the process and position

During welding (in-process):

• Interpass cleaning is adequate
• Interpass temperature within limits
• Each pass has acceptable profile
• No visible cracks or defects

After welding (final VT):

• Complete visual examination against the Clause 8 acceptance criteria
• Check weld size, length, location against the drawings
• Verify profiles, check for undercut, porosity, cracks, overlap

Non-Destructive Examination (NDE)

D1.1 Clause 6 specifies when NDE beyond VT is required:

Radiographic Testing (RT): For CJP groove welds, particularly in tension members, as specified by the engineer

Ultrasonic Testing (UT): Can substitute for RT on most structural welds. UT is faster for thick material and doesn’t create radiation hazards

Magnetic Particle Testing (MT): For detecting surface and near-surface cracks. Often used on moment connection welds, demand-critical welds, and repair areas

Liquid Penetrant Testing (PT): For non-magnetic materials or when MT equipment isn’t available. Less sensitive than MT for ferromagnetic steels

The extent of NDE (percentage of welds tested, which joints require NDE) is specified by the Engineer of Record on the drawings or in the project specification. D1.1 provides guidelines, but the EOR makes the final call.

Acceptance Criteria (Clause 8)

Static Loading (Table 8.9)

Cyclic Loading (Table 8.11)

Structures subject to fatigue (bridges, crane runways, structures with repeated loading cycles) have tighter limits:

• Undercut: 0.01 inch max
• Porosity limits more restrictive
• Profile requirements more stringent
• Certain defect combinations rejected that would pass for static loading

Field vs. Shop Welding

Shop Welding

Shop welding has controlled conditions: fixed equipment, overhead crane access, temperature-controlled environment, and proximity to inspection tools. Shops produce more consistent welds because:

• Workpieces can be positioned optimally (flat or horizontal welding is preferred over vertical and overhead)
• Preheat is easier to apply and maintain
• Ventilation and lighting are controlled
• Equipment is well-maintained and accessible

Field (Erection) Welding

Field welding has unique challenges:

• Position: Welds are made in whatever position the structure requires. Vertical and overhead welding is common
• Weather: Wind, rain, cold, and heat affect both the welder and the weld quality. GMAW and GTAW are difficult in windy conditions. Preheat in cold weather requires more fuel and time
• Access: Tight spaces, elevated work, congested areas. The welder may not have optimal body position
• Sequencing: Weld sequence may be dictated by erection order, not welding preference

D1.1 addresses field conditions specifically:

• Welding shall not be performed when ambient temperature is below 0F unless the WPS accounts for it
• Base metal surface must be dry within 3 inches of the joint
• Wind protection is required for gas-shielded processes (GMAW, FCAW-G, GTAW)

Documentation Requirements

A compliant D1.1 welding program maintains:

1. WPSs for every welding procedure used (prequalified or qualified)
2. PQRs for all qualified WPSs
3. Welder qualification records including continuity logs
4. Inspection reports (VT, NDE results)
5. Material test reports (MTRs) for base metals and filler metals
6. Non-conformance reports (NCRs) for rejected welds and their repair disposition
7. Heat treatment records (when PWHT is required)

This documentation must be available for review by the Engineer of Record, the owner’s inspector, and any code authority having jurisdiction. “If it isn’t documented, it didn’t happen” is the governing principle. Structural welding is quality-documented work, and the paperwork is as much a part of compliance as the welds themselves.