In Canada, structural steel fabrication is governed by CSA S16, "Design of steel structures," which the National Building Code and the 2024 Ontario Building Code reference (the OBC references S16-19). S16 sets out how members are designed and also how they are detailed, fabricated, welded, bolted, erected and inspected. Welding is done to CSA W59 by companies certified to CSA W47.1 by the CWB Group, and the steel itself is supplied to CSA G40.20/G40.21 or recognized ASTM standards.
This post is the shop-floor view: what each standard asks of the fabricator, and what you can ask for as a buyer. For how the building code calls up these standards and which edition applies, see our overview of Canadian structural steel codes.
The standards a steel shop works to
| Standard | What it covers in the shop |
|---|---|
| CSA S16 | Design, plus shop drawings, fabrication, tolerances, welding and bolting requirements, erection and inspection |
| CSA G40.20/G40.21 | Structural quality steel: grades such as 350W, plus general requirements and tolerances |
| ASTM A6/A6M | Rolling tolerances for structural shapes, referenced by G40.20 |
| ASTM A992, A500 and others | Common ASTM grades for W-shapes and HSS, recognized by S16 |
| CSA W59 | Welded steel construction: weld design, procedures, workmanship and inspection |
| CSA W47.1 | Certification of companies that fusion weld steel |
| CSA W55.3 | Certification of companies doing resistance welding |
| CSA W48 | Welding electrodes and filler metals, which the CWB Group certifies |
| CSA W178.1 and W178.2 | Certification of welding inspection organizations and of welding inspectors |
| ASTM F3125 | High-strength structural bolts (the standard that now covers A325 and A490 grades) |
| ASTM F1554 | Anchor rods (Grades 36, 55 and 105) |
| CSA A660 | Certification of manufacturers of steel building systems |
| CISC Code of Standard Practice | Commercial practice: scope of supply, shop drawing approval, responsibilities |
Not every job touches every standard. A basement beam with welded plates involves S16, G40.21 (or A992), W59 and W47.1. A commercial frame adds bolting standards, inspection requirements and the CISC Code of Standard Practice through the specification.
What CSA S16 asks of the fabricator
People think of S16 as a design standard, but a large part of it is aimed at the shop and the erector. Broadly, it covers:
- Shop drawings. Drawings prepared from the design documents showing every piece, connection, weld and bolt, reviewed before fabrication.
- Material. Steel to the referenced standards, identified so it can be traced to the grade specified. CISC cautions that strength values on mill test certificates should not be used as the basis for design; the specified minimum values are.
- Fabrication. Cutting, holing, fit-up, straightening and cambering, with tolerances on length, straightness and end preparation.
- Welding. Qualification of fabricators and erectors of welded construction is set out in Clause 24.3 of S16, the clause the Ontario Building Code's explanatory notes point to. It is the link to CWB certification.
- Bolting. Bolt installation, pretensioning where required, and inspection procedures.
- Column bases. For example, S16-14 required at least four non-collinear anchor rods per column for erection safety, as CISC notes in its guidance.
- Erection and inspection. Requirements for erection tolerances and stability, and for inspection of the work.
Tolerances get their own guide: see steel fabrication tolerances under CSA S16, and for beams, camber tolerances and natural mill camber.
Welding: W59 and W47.1
Two welding standards do different jobs:
- CSA W59 governs the welds. It covers how welded joints are designed, which processes and consumables may be used, how procedures are qualified, workmanship standards and weld inspection. Studs welded under W59 must be qualified through a CWB Group program. Our guide to CSA W59 goes deeper.
- CSA W47.1 governs the company. The CWB Group reviews the company's welding procedures, qualifies its welders and supervisors, requires engineering responsibility for welding in Divisions 1 and 2, and audits the shop. See CSA W47.1 and CWB company certification.
Consumables are part of the chain too. CSA W48 sets out requirements for welding electrodes and filler metals, and the CWB Group certifies consumables against it. Shop welding procedures name the certified consumables they use.
For S16 work, the fabricator and erector responsible for welding must be certified to W47.1 in Division 1 or 2 (or to W55.3 for resistance welding), as applicable. Our post on why to hire a CWB-certified fabricator explains the divisions and how to check a certificate.
Materials and mill certificates
Most Canadian structural steel is supplied to one of two families of standards:
- CSA G40.21, with grades named by minimum yield strength in MPa, such as 350W.
- ASTM, such as A992 for W-shapes and A500 for HSS.
CISC notes that North American mills commonly certify W-shapes to both ASTM A992 and CSA G40.21 350W. HSS is less interchangeable: CISC cautions that an A500 HSS is not an exact substitute for a G40.21 350W section of the same nominal size, because of its looser under-mass tolerance and, in some cases, lower tensile properties. If a substitution is proposed, the engineer decides.
Mill test certificates show the chemistry and mechanical test results for the heat of steel supplied. Ask for them when you order if your specification requires traceability. Our guide to HSS steel grades covers the HSS side in more detail.
Inspection and quality assurance
S16 does not require third-party inspection on every job. What it requires is that the fabricator controls quality and that the work meets the standard. Third-party inspection is added by the project specification.
CSA S16-19 introduced an informative Annex P, which gives engineers guidance on specifying third-party inspection. As CISC explains, the engineer selects an inspection class from IC1 to IC4 based on the required reliability, the type of structure and the loading, and Annex P suggests inspection frequencies for welds, bolted connections and general workmanship in the shop and field. Because it is informative, it applies only when the specification adopts it.
Who pays matters. CISC points engineers to the CISC Code of Standard Practice, which states that the cost of inspection and testing is the client's responsibility, while re-inspection and re-testing caused by deficiencies in the fabricator's or erector's work is borne by them.
The CISC Code of Standard Practice
The CISC Code of Standard Practice for Structural Steel is not a law or a CSA standard. It is the industry's rulebook for commercial practice, and specifications often adopt it. It defines what is included in "structural steel," how shop drawings are submitted and approved, who supplies what, and how responsibilities and costs are split. When a quote or contract refers to it, read the relevant clauses, because they shape what you are buying.
What to ask your fabricator for
When you compare fabricators, these questions cover the standards in a few minutes:
- CWB certification: which standard and division, and a current certificate.
- Shop drawings: prepared in-house or outsourced, and how they are submitted for review.
- Material: which grades they will supply against your drawings, and whether mill certificates are available.
- Inspection: whether your specification requires third-party inspection, and how hold points will be coordinated.
- Tolerances and camber: any special requirements in your specification.
Our checklist on choosing a structural steel fabricator in Ontario covers the rest.
Fabrication to the drawings and the standards
Our shop welding is certified by the Canadian Welding Bureau, our shop drawings are done in-house, and engineering services are available for projects that need them. Every piece is cut, fitted, welded and marked to match the drawings.
Send us your structural drawings for a free take-off and quote, or see our steel products and services.
Frequently asked questions
What is the structural steel fabrication code in Canada?
CSA S16, Design of steel structures, which the building codes reference. Besides design rules, it covers shop drawings, fabrication, welding, bolting, erection and inspection, and it brings in CSA W59 for welding and CSA W47.1 for welding company certification.
Is CSA W47.1 required for structural steel fabrication?
For welded structural steel designed to CSA S16, the fabricator and erector responsible for welding must be certified by the Canadian Welding Bureau to CSA W47.1 Division 1 or 2 (or W55.3 for resistance welding), as applicable. Part of the work may be sublet to a Division 3 company.
What is the difference between CSA W59 and W47.1?
W59 governs the welds themselves: design, workmanship, procedures and inspection. W47.1 governs the company: its procedures, supervisors, engineering responsibility, welder qualifications and audits by the CWB Group.
Does structural steel need third-party inspection in Canada?
Only if the project specification requires it. CSA S16-19 added an informative Annex P that helps engineers specify third-party inspection by inspection class. The engineer or owner normally selects and pays the inspection agency.
What paperwork should a steel fabricator provide?
Typically shop drawings for approval, proof of CWB certification, mill test certificates if the specification asks for them, and any inspection or test reports the specification calls for. Ask at the quote stage so nothing is missed.
