Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Comprehensive Guide to CSA G40.20-13 (R2018) & CSA G40.21-13: General Requirements and Structural Quality Steels
Understanding the Canadian Standards for Structural Steel – Categories, Mechanical Properties, and Compliance
CSA G40.20-13 (R2018) General requirements for rolled or welded structural quality steel and CSA G40.21-13 Structural quality steels are the twin pillars of structural steel specification in Canada. Together, they define the mechanical properties, chemical composition, manufacturing processes, and inspection criteria for steel products used in buildings, bridges, and other engineered structures. These standards are referenced by the National Building Code of Canada (NBCC) and are considered equivalent to ASTM A36/A572 within the Canadian regulatory framework. This article provides a technical overview of the scope, key requirements, practical implementation, and compliance notes for engineers, fabricators, and quality assurance professionals.
Scope and Application
CSA G40.20-13 (R2018) establishes the general delivery conditions, testing procedures, and acceptance criteria that apply to all structural quality steels supplied under the G40 series. It covers manufacturing processes (hot‑rolled, cold‑drawn, heat‑treated), chemical analysis, mechanical testing, dimensional tolerances, and repair by welding. CSA G40.21-13, in turn, lists the specific steel grades – each with its own required strength, toughness, and weldability characteristics – that are produced and tested in accordance with G40.20.
The standards apply to:
- Plates, shapes, hollow structural sections (HSS), bars, and sheet piling
- Carbon and low‑alloy steels intended for welded and non‑welded structures
- Categories ranging from general structural (W) to atmospheric corrosion‑resistant (A), low‑temperature tough (WT), and quenched & tempered (Q & QT)
- Both metric and imperial units (SI primary, imperial acceptable by agreement)
Key Distinction: G40.20 is the “umbrella” standard that dictates how every steel grade listed in G40.21 must be produced and verified. Always consult both standards together.
Technical Requirements and Material Categories
Steel Categories and Designations
CSA G40.21-13 defines grades using a number‑letter system. The number indicates the minimum yield strength (MPa) in the as‑rolled condition, and the letter denotes the application category:
| Grade | Min. Yield (MPa) | Tensile (MPa) | Elong. (%) | Category | Typical Application |
|---|---|---|---|---|---|
| 300W | 300 | 450–620 | 21 | Weldable | General structures, beams |
| 350W | 350 | 480–650 | 20 | Weldable | Bridges, high‑rise buildings |
| 350A | 350 | 480–650 | 20 | Atmospheric corrosion‑resistant | Exposed steel (weathering) |
| 350WT | 350 | 480–650 | 20 | Weldable, low‑temperature toughness | Arctic service, seismic zones |
| 400W | 400 | 520–700 | 19 | Weldable | Heavy machinery, columns |
| 500Q | 500 | 600–750 | 17 | Quenched & tempered | High‑strength frames, mobile equipment |
Additional categories include GR (general purpose), AT (atmospheric corrosion‑resistant with low‑temp toughness), and QT (quenched & tempered with finer grain size). For each grade, G40.20 limits carbon equivalent (CE) to assure weldability, and requires Charpy V‑notch impact testing for WT and AT grades at specified temperatures (e.g., −20°C, −40°C).
Mechanical Testing and Heat Treatment
G40.20 mandates that each heat and thickness be tested in accordance with ASTM A370 / CSA W48. Tensile tests are performed on full‑thickness specimens or round bars. Bend tests are required for flat products. When heat treatment is specified (normalizing, quenching and tempering), the standard prescribes furnace temperatures, cooling media, and hardness ranges.
Heat Treatment Consideration: For grade 500Q, the quenching rate must be sufficient to achieve a martensitic structure at the core, followed by tempering at not less than 600°C. Fabricators should verify that thermal cutting and welding do not degrade the as‑heat‑treated properties.
Implementation Highlights for Fabricators and Engineers
Successful application of CSA G40.20‑G40.21 requires careful attention to the following during design and fabrication:
- Item Identification: Every steel piece must be marked with the grade, heat number, and manufacturer’s name. Colour‑coding per CSA G40.20 Table 4 is optional but common.
- Welding Procedure: Use CSA W59 (welded steel structures) or CSA W47.1 (fusion welding) to qualify procedures. Grades 300W and 350W have CE ≤ 0.40%, allowing preheat typically only for thick sections. For 500Q, strict hydrogen control and preheat are mandatory.
- Dimensional Tolerances: Flatness, camber, and sweep tolerances follow ASTM A6, except where G40.20 specifies tighter limits for ultra‑heavy plates (t > 100 mm).
- Repair Welding: Defects may be gouged and re‑welded provided the repair is performed to an approved procedure and the area is inspected by MT or UT per G40.20 Clause 8.5.
Best Practice: When ordering steel to CSA G40.21, always specify the category letter (e.g., 350W vs. 350A) and any supplemental requirements such as impact testing at −30°C or ultrasonic inspection. This ensures the delivered material meets the exact project conditions.
Compliance Notes and Certification
Compliance with CSA G40.20‑G40.21 is verified through:
- Material Test Reports (MTRs): Must include heat number, chemical analysis, tensile and impact results, and the statement “meets CSA G40.21‑13 / G40.20‑13”.
- Third‑Party Certification: For projects under NBCC jurisdictional scope, steel must be produced by mills listed by the Canadian Steel Certification Program (CSA S16‑recommended).
- Traceability: Each piece must remain linked to its MTR until incorporation into the structure. Electronic tagging systems are acceptable.
- Non‑Conformance: If a test fails, the mill may re‑test two additional samples from the same heat. If both pass, the lot is accepted; if one fails, the lot is rejected or may be downgraded to a lower grade (e.g., 350W → 300W).
Non‑Compliance Risk: Using material that does not meet G40.20 traceability requirements can void the engineer’s certification under NBCC and expose the project to unacceptable liability. Always request full MTRs and verify them against the standard’s tables.
In addition, the latest edition of the standard allows the use of both SI (MPa, mm) and imperial (ksi, in) units, but all official test reports must report SI values. Engineers specifying older grades (e.g., 260W from previous editions) should confirm availability with the mill, as many have been discontinued.
Q: What is the difference between CSA G40.20 and G40.21?
A: CSA G40.20 covers the general delivery requirements – testing, tolerances, marking – that apply to all structural steels, while CSA G40.21 lists the specific grades with their mechanical and chemical requirements. G40.20 is analogous to ASTM A6, and G40.21 is analogous to ASTM A36/A572. Both must be applied together; G40.21 references G40.20 for all generic requirements.
A: CSA G40.20 covers the general delivery requirements – testing, tolerances, marking – that apply to all structural steels, while CSA G40.21 lists the specific grades with their mechanical and chemical requirements. G40.20 is analogous to ASTM A6, and G40.21 is analogous to ASTM A36/A572. Both must be applied together; G40.21 references G40.20 for all generic requirements.
Q: Can CSA G40.21 steel be used interchangeably with equivalent ASTM grades?
A: For many grades there is a close match (e.g., 300W ↔ A36/240 MPa, 350W ↔ A572‑50). However, the Canadian standard often specifies tighter carbon equivalent limits and different impact test temperatures. Designers must verify that the selected grade meets all NBCC load and toughness requirements; substitution requires engineering approval.
A: For many grades there is a close match (e.g., 300W ↔ A36/240 MPa, 350W ↔ A572‑50). However, the Canadian standard often specifies tighter carbon equivalent limits and different impact test temperatures. Designers must verify that the selected grade meets all NBCC load and toughness requirements; substitution requires engineering approval.
Q: Are impact tests required for all grades?
A: No. Only categories WT, AT, and certain Q grades require Charpy V‑notch testing by default. The standard allows the buyer to request impact testing for any grade at a specified temperature – this is common for seismic and arctic applications. For grades W and A, impact testing is not mandatory unless the project specification requires it.
A: No. Only categories WT, AT, and certain Q grades require Charpy V‑notch testing by default. The standard allows the buyer to request impact testing for any grade at a specified temperature – this is common for seismic and arctic applications. For grades W and A, impact testing is not mandatory unless the project specification requires it.
Q: What edition of these standards is currently used for building in Canada?
A: As of 2026, the 2013 editions of both standards are still current. CSA G40.20‑13 was reaffirmed in 2018 (hence “R2018”), and CSA G40.21‑13 remains unchanged. Fabricators should always check the latest NBCC supplement to see if a newer version has been adopted for their jurisdiction.
A: As of 2026, the 2013 editions of both standards are still current. CSA G40.20‑13 was reaffirmed in 2018 (hence “R2018”), and CSA G40.21‑13 remains unchanged. Fabricators should always check the latest NBCC supplement to see if a newer version has been adopted for their jurisdiction.
This article is published for educational purposes and does not replace the official CSA standards. Always refer to the authoritative documents for full regulatory compliance.
© 2026 – Technical reference review. Standards referenced: CSA G40.20‑13 (R2018) and CSA G40.21‑13.