Structural vs. Nonstructural Steel: The Short Answer
Structural steel carries or resists the loads that keep a building or machine stable. Think beams, columns, bracing and primary equipment frames. Nonstructural steel, often called miscellaneous steel, supports no primary load. Trim, cladding, guards and light brackets are typical examples. In short, structural steel carries primary loads and must meet CSA or AISC standards with certified welding, while nonstructural steel doesn't carry primary loads and has lighter requirements.
In Canada, structural steel is generally produced to CSA G40.20/G40.21 (commonly grade 350W), designed to CSA S16, and welded by a firm certified to CSA W47.1 that follows CSA W59. Ontario Building Code compliance applies to structural work. Across the border, the equivalents are ASTM A36 and A992 for W-shapes, A500 for hollow structural sections (HSS), and AISC specifications. They're close, but they aren't interchangeable without engineering review.
Getting the classification wrong is expensive either way. Under-specify a part and you risk safety problems and failed inspections. Over-specify it and you add cost and lead time you didn't need.
This guide gives you a six-criteria evaluation method, red flags to watch for, a decision checklist and answers to common questions. We're BSG Inc, a Kitchener, Ontario fabricator operating since 1987, and we draw on that experience throughout. If you want to see what our structural steel fabrication work covers, that page shows the applications and capabilities in detail.
How to Evaluate: 6 Criteria for Classifying Steel
Six criteria separate structural from nonstructural steel: load path, material grade and shape, code and design standards, welding and certification, inspection and tolerances, and cost and lead time. Work through them in order, because the first one settles most cases.
1. Load path
Ask one question: if this part failed, would it affect the stability or safety of people, a building or a machine? If yes, treat it as structural. Beams, columns, trusses, bracing, crane runway supports and mining equipment frames all qualify. If you're new to framing concepts, our steel framing guide explains how load-bearing members work together.
2. Material grade and shape
Structural work uses W-shapes, HSS, channels, angles and plate. In Canada that usually means CSA G40.21 350W. In US-based specifications you'll see ASTM A992 for W-shapes, A500 for HSS, and A36 for plate and angles. Structural material should arrive with mill test reports that trace it to a heat and grade.
Nonstructural parts often use sheet, light-gauge or commercial-quality steel. Our overview of steel grades for sourcing covers those options. Galvanized steel is also common for cladding, trim and finishes, and galvanized steel uses are worth a read if corrosion resistance matters to your project.
3. Code and design standards
Structural members are designed to CSA S16 and the Ontario Building Code, and they often require engineer-stamped drawings. Nonstructural items usually need dimensional drawings only, unless they attach to primary structure. That attachment detail matters: a light bracket that bolts to a column may be simple, but the connection to the column isn't.
4. Welding and joining
Structural welds require a fabricator certified to CSA W47.1 (Division 1 or 2 in practice), with procedures that meet CSA W59 and qualified welders. AWS D1.1 is the US counterpart. Our article on CWB-certified structural welding shows what qualified work looks like.
Nonstructural welds still need good workmanship, but the paperwork is lighter. For background on joining methods, see how steel is welded. Welding heat can also change the steel next to the weld. That heat-affected zone is why procedure control matters on load-bearing joints.
5. Inspection and tolerances
Structural work carries tighter tolerances, weld inspection (visual, magnetic particle or ultrasonic testing as specified) and documentation. Nonstructural work typically gets visual checks and looser tolerances.
6. Cost and lead time
Structural steel costs more per tonne because of engineering, certification, testing and detailing. Our beam fabrication costs guide breaks down those drivers, and plate fabrication pricing shows how heavier plate work differs from light nonstructural jobs. Nonstructural is quicker and cheaper, but the savings vanish if a part has to be reclassified later.
The table below compares the two categories side by side.
| Attribute | Structural steel | Nonstructural steel |
|---|---|---|
| Load-bearing | Carries primary loads | No primary load |
| Standards | CSA S16, G40.21, W59 (AISC in US) | Dimensional drawings, basic workmanship |
| Typical grades | 350W, A992, A500, A36 | Sheet, light-gauge, commercial quality |
| Welding certification | CSA W47.1 (AWS D1.1 in US) | Not usually required |
| Inspection | Visual, MT, UT, mill certs | Mainly visual |
| Typical applications | Beams, columns, bracing, equipment frames | Trim, cladding, guards, light brackets |
Gray-area items
Some parts get misclassified more than others: stairs, handrails and guards (code-driven loads often make them structural-grade), platforms and mezzanines, lintels, equipment frames, and supports for rooftop units. When in doubt, ask the engineer of record.
Red Flags When Specifying or Sourcing Steel
Most sourcing problems show up early if you know where to look. Watch for these:
- No current certification. The fabricator can't show a current CWB certificate under CSA W47.1 or documented welding procedures for structural work.
- No traceability. Plate and sections supplied as structural have no mill test reports or grade traceability.
- Missing engineering. Quotes for stairs, platforms or lintels arrive with no engineered drawings or stated design loads.
- Pricing far below the rest. That often signals nonstructural-grade material, skipped inspection or uncertified welders.
- Mixed grade systems. Drawings combine ASTM and CSA grades without an equivalence approved by the engineer.
- Vague liability answers. Nobody can say who's responsible if a part is reclassified as load-bearing. For structural work, liability sits with the designer and fabricator.
- Limited capacity. The shop lacks cranes or CAD and 3D modelling for large, heavy assemblies, which causes delays and outsourced quality gaps.
That last point matters most on high-load work. Mining and heavy industrial projects show why experience counts, and our piece on mining equipment structural fabrication shows how steel selection plays out in that setting. Before you award any structural job, review what to expect from a certified contractor in our CWB-certified structural welding contractor guide.
Structural vs. Nonstructural Steel Decision Checklist
Answer these seven questions for each part. The first three decide the classification, and the rest confirm you can source it properly.
- Does the part carry, transfer or brace loads (dead, live, snow, wind, seismic or equipment)? Yes or no.
- Would failure endanger people or stop production? Yes or no.
- Is the part attached to primary structure or covered by Ontario Building Code requirements? Confirm with the engineer. Yes or no.
- Are the grade, shape and standard (CSA G40.21 350W, ASTM A992, A500 or A36) stated on the drawings?
- Is the fabricator CWB certified to CSA W47.1, with welding procedures that match your joints?
- Are inspection and documentation requirements (NDT, mill certs, tolerances) defined?
- Have you compared cost and lead time for both options, including the cost of rework?
Scoring rule: any "yes" to questions 1 to 3 means specify structural. If all three are "no," nonstructural is likely acceptable. Questions 4 to 7 then tell you whether your documents and supplier are ready.
One more decision sits alongside this checklist: custom or standard components. A custom design can fit the load and geometry exactly, while an off-the-shelf product may ship faster. Our comparison of custom vs. off-the-shelf equipment helps you weigh load, schedule and budget. For short runs or trial parts, our small-batch fabrication service and prototype articles show how to test a design before committing.
Choosing a Fabrication Partner That Meets Every Criterion
The criteria above are easier to meet when one shop covers them all. BSG Inc has fabricated since 1987 and holds CWB and AWS certifications with more than 30 welding procedures, so structural joints are welded to documented procedures.
Our 44,000 sq ft Kitchener facility has extensive crane capacity for heavy assemblies across mining, automotive, construction and industrial process equipment. SolidWorks 3D modelling, CAD and 3D printing support early design review, which helps classify parts before they reach the shop floor. Just-in-time delivery and competitive pricing protect your schedule and budget, and our long-term client relationships reflect that reliability.
Once you've decided which steel type your project needs, vet vendors with our guide on how to choose a metal fabrication vendor, then request a quote with your drawings and design loads.
Frequently Asked Questions
What is the difference between structural and nonstructural steel?
Structural steel carries primary loads and is made to standards such as CSA G40.21 or ASTM A992, designed to CSA S16 and welded by certified fabricators. Nonstructural steel does not carry primary loads, such as trim, cladding, guards and light brackets, and has lighter requirements.
Are stairs and handrails structural steel?
Often they are treated as structural or near-structural because code loads apply and they connect to the building frame. The engineer of record and the Ontario Building Code determine requirements, so confirm before quoting.
Does structural steel fabrication require CWB certification in Ontario?
Structural welding for buildings is generally done by firms certified to CSA W47.1 and following CSA W59. Specifications and the authority having jurisdiction set the final requirement.
Is ASTM A36 the same as CSA G40.21 350W?
No. A36 has a minimum yield of 250 MPa while 350W is 350 MPa. Substitution needs engineering approval.
Which is more expensive, structural or nonstructural steel?
Structural costs more because of engineering, certified welding, traceable material and inspection. Choosing nonstructural for a load-bearing part can cost more later through rework.
Are HSS and W-beams always structural?
They are structural shapes, but use depends on the application. A W-beam or HSS in a frame is structural; an HSS used as a decorative rail may not be.