Structural welding is different from general welding in one important way: the welds are load-bearing. If a weld fails on a handrail, it's a hazard. If a weld fails on a structural connection, it can be catastrophic. The qualifications, the process, and the documentation requirements all reflect that difference.
This guide is written for the builder or project manager — the person who needs to understand what they're specifying, how to verify compliance, and what information to give a structural welder to get a clean outcome.
What Is Structural Welding?
Structural welding joins load-bearing steel elements — beams, columns, connection plates, base plates, bracing, trusses. The key distinction from decorative or repair welding is that structural welds are engineered: they have a specified size, throat, and quality category determined by a structural engineer's design.
A structural weld that's undersized, poorly fused, or contains internal defects can carry the load in the short term and fail under fatigue or dynamic loading. This is why standards and certification exist.
The Relevant Standard: AS/NZS 1554
AS/NZS 1554 is the primary Australian standard for structural steel welding. It has multiple parts:
- AS/NZS 1554.1 — Welding of steel structures. Covers most structural steel welding on buildings and bridges.
- AS/NZS 1554.5 — Welding of steel structures subject to high levels of fatigue loading (cranes, dynamic equipment)
- AS/NZS 1554.6 — Welding of stainless steel
AS/NZS 1554.1 classifies welds into three categories: SP (structural purpose — highest quality), GP (general purpose), and TF (tension force members). Your engineer's drawings will specify which category applies to each weld on the project.
SP category welds require the highest standard of preparation, execution, and inspection. GP welds have more allowable variation. If your drawings don't specify a category, ask the engineer — it matters for how the work is inspected.
Pre-Qualified Weld Procedures
AS/NZS 1554.1 includes a set of pre-qualified weld procedures — weld joint designs and parameters that are deemed acceptable without requiring a formal weld procedure qualification test. This speeds up the process for standard structural steel work: the welder follows the pre-qualified procedure and the engineer accepts it.
For non-standard materials, unusual joint configurations, or high-performance applications, a formal Welding Procedure Qualification Test (WPQT) may be required. This is documented in a Welding Procedure Specification (WPS) and qualified by testing a weld coupon. On major projects, the structural engineer will specify whether pre-qualified or qualified procedures are required.
Qualified vs Coded Welder: What You Actually Need
The terminology is often confused. Here's the distinction:
- Trade-qualified welder: Holds Certificate III in Engineering – Fabrication Trade. Competent for general fabrication and repair work, including most residential structural welding.
- Qualified welder under AS/NZS 1554: Has demonstrated competency in the specific weld process, position, and material group required by the project. This may be documented through records of prior testing and ongoing work.
- Coded welder (ISO 9606-1 or AS 1796): Has passed a formal independent welder qualification test in specific parameters. This is what structural engineers and contract specifications typically require for SP category structural welding.
In practice, for commercial or government structural steel work in Sydney, your specification will require a coded welder. For residential structural connections (adding a post, installing a steel beam, repairing a frame), a trade-qualified welder with structural experience is usually sufficient — but check with your structural engineer if the load path is significant.
For more detail on certifications and what they cover, see our guide to welding certifications in Australia.
On-Site vs Workshop for Structural Welding
The choice of where structural welding happens has real implications:
Workshop fabrication is preferred for complex assemblies where precision is critical — portal frames, trusses, repetitive connection plates. A workshop has jigs, fixed welding positions, better lighting and ventilation, and quality control processes.
On-site welding is necessary for connections that can only be made once the steelwork is in its final position — column base plates, beam-to-column connections, post-to-footing plate welds. In-situ structural repairs after installation also require mobile or on-site welding.
The practical approach for most Sydney construction projects is hybrid: workshop-fabricate the components, crane into position, and weld the connections on-site. This is the most efficient and quality-controlled approach for most building structural steel scopes.
Common Structural Applications for Mobile Welders
- Column and post base plate welds (in-situ, after grout sets)
- Beam splice connections for staged erection
- Cleats and connection plates welded in-situ to existing structure
- Structural repairs to existing buildings — cracked or damaged steel members
- Adding to existing structural frames — mezzanine additions, carport structures
- Tie rod and bracing installation
Documentation and Inspection
For commercial structural work, the welder should provide:
- Welder qualification records (certificates with process, position, and material scope)
- Weld records showing weld locations, processes used, and parameters (voltage, amperage, wire feed)
- As-built weld maps if specified
Inspection requirements vary by category. SP welds typically require visual inspection as a minimum, and may require non-destructive testing (magnetic particle, ultrasonic, or radiographic inspection) depending on the structural engineer's specification. Arrange for inspection to be carried out before areas are concealed (by sheeting, concrete, etc.).
How to Brief a Structural Welder — 7 Things to Include
Getting a clean outcome starts with a clear brief. Provide the welder with:
- Drawing references — Issued-for-Construction structural drawings showing the weld locations, sizes, and categories
- Material specification — Steel grade (typically Grade 350 for structural steel in Australia), surface coating if any (hot-dip galv, primer), and condition of existing steel if it's a repair
- Required weld category — SP or GP (from the structural drawings)
- Access and clearances — What equipment can reach the weld location; height access requirements; confined space or hot work permit requirements
- Inspection requirements — Who inspects, at what stage, and what the acceptance criteria are
- Programme constraints — Sequence requirements (can't weld connection A before column B is in position), critical path items
- SWMS requirements — Whether a project-specific Safe Work Method Statement is required from the welder, or whether the site SWMS covers it
The more specific the brief, the more accurate the quote and the less room for programme delays or scope disputes. For emergency structural repairs where time is critical, see our emergency mobile welding guide.
To understand material choices for structural work, see steel vs aluminium vs stainless for a comparison of structural properties and applications.
For the structural welding service, see our structural welding page or contact us through the mobile welding service page. Call 0426 829 762 to discuss your project scope.