Structural steel is the backbone of modern construction—the load-bearing framework that holds up buildings, bridges and industrial structures. Unlike decorative steel or the steel used in vehicles and machinery, structural steel is manufactured to strict standards for strength, composition and performance. It is engineered specifically to carry weight and resist forces.
Below, we explain what makes steel “structural,” the different types and grades available, where it is used, and why it matters for your build—so you can make informed decisions with confidence.
What is Structural Steel?
Structural steel is a category of steel manufactured to meet specific standards for composition and dimensional accuracy. It is used for load-bearing elements in construction—the beams, columns, trusses, joists and frames that support walls, floors and roofs.
What Makes Steel “Structural”?
The key difference between structural steel and other types of steel lies in its carbon content and composition. Structural steel typically contains between 0.05% and 0.25% carbon by weight. This low carbon content gives it the right balance of strength, ductility and weldability for construction applications.
Steel with higher carbon content becomes harder and more brittle, making it unsuitable for structural use. Steel with too little carbon lacks the necessary strength. Structural steel sits in the sweet spot—strong enough to carry loads, flexible enough to absorb energy without fracturing, and workable enough to fabricate and weld on site.
In Australia, structural steel must meet standards set by Standards Australia (AS/NZS).
Key Characteristics
- High strength-to-weight ratio – Steel carries large loads with less bulk than concrete or timber, reducing strain on foundations.
- Dimensional accuracy – Factory-manufactured elements arrive straight and true, with minimal variation.
- Consistent quality – Engineered to strict standards with predictable performance.
- Ductility – Can absorb energy and flex under load without brittle failure.
- Weldable and workable – Can be cut, drilled, bolted and welded on site or prefabricated off-site.
Common Types and Grades of Structural Steel
Not all structural steel is the same. Different grades and types are suited to different applications based on strength, corrosion resistance and working environment.
Mild Steel (Low Carbon Steel)
Mild steel contains up to 0.25% carbon and is the most commonly used structural steel. It is relatively soft, easy to work with, and cost-effective. Mild steel is ideal for general-purpose structural applications like beams, columns and frames in residential and commercial buildings.
Typical strength: Around 400 MPa tensile strength
Common uses: Building frames, trusses, columns, general fabrication
Carbon Steel
Carbon steel is classified by its carbon content:
- Low carbon (0.05–0.25%) – Similar to mild steel; easy to weld and form
- Medium carbon (0.3–0.6%) – Stronger and harder; more difficult to weld
- High carbon (0.6–1.5%) – Very hard and strong; used for cutting tools, springs and wires rather than structural work
For structural applications, low carbon steel is preferred because it balances strength with workability.
High-Strength Low-Alloy (HSLA) Steel
HSLA steel contains small amounts of alloying elements like copper, nickel, chromium or vanadium. These elements boost strength and toughness without significantly increasing weight or cost. HSLA steel is used where higher strength is needed—such as in high-rise buildings, bridges and heavy industrial structures.
Typical strength: 450–700 MPa tensile strength
Common uses: High-rise frames, bridges, crane booms, heavy equipment
Stainless Steel
Stainless steel contains at least 10.5% chromium, making it highly resistant to corrosion, staining and rust. While more expensive, it is ideal for structural applications in harsh or corrosive environments—coastal zones, chemical plants, food processing facilities.
Common uses: Coastal structures, marine environments, industrial facilities
Weathering Steel (COR-TEN)
Weathering steel is a high-strength, low-alloy steel designed to develop a stable rust layer that protects the underlying steel from further corrosion. It is commonly used for outdoor structures where long-term exposure to the elements is expected.
Common uses: Bridges, outdoor sculptures, building facades, retaining walls
Common Australian and International Grades
- AS/NZS 3678 Grade 250 – General-purpose structural steel, 250 MPa minimum yield strength
- AS/NZS 3678 Grade 350 – Higher strength, 350 MPa minimum yield strength
- ASTM A36 (International) – Equivalent to AS/NZS 250, widely used in buildings and bridges
- ASTM A572 (International) – Higher strength grade, commonly used in structural frames
Engineers select grades based on the loads, spans and environmental conditions of each project.
Structural Steel Products and Elements
Structural steel comes in a wide range of shapes and sections, each designed for specific structural roles:
- Universal Beams (I-beams) – Horizontal load-bearing members; used for floors and roofs
- Universal Columns (H-beams) – Vertical load-bearing members; support building weight
- Channels (C-sections) – Used for bracing, framing and secondary support
- Angles (L-sections) – Corner bracing, supports, connections
- Hollow Sections (RHS, SHS, CHS) – Rectangular, square or circular tubes; used for columns, trusses and architectural elements
- Steel Plates – Flat sheets used for connections, gusset plates and fabrication
- Steel Trusses – Prefabricated triangulated frameworks for roofs and floors
- Steel Frames – Prefabricated wall and floor framing systems
At Steel Frames WA, we manufacture and supply wall frames, roof trusses and floor joists from structural steel—engineered specifically for WA conditions and backed by over 50 years of building expertise.
Where is Structural Steel Used?
Structural steel is used across virtually every sector of construction:
- Residential buildings – Frames, trusses, floor joists, second-storey additions, tiny homes
- Commercial buildings – Office towers, retail centres, warehouses, factories
- Industrial structures – Sheds, mining facilities, processing plants
- Infrastructure – Bridges, transmission towers, road and rail supports
- Agricultural buildings – Sheds, barns, livestock facilities
In Western Australia, structural steel is especially valuable because it resists termites, withstands cyclonic conditions in the north, and performs well in coastal and bushfire-prone zones.
Why Choose Structural Steel for Your Build?
1. Strength and Durability
Steel does not warp, shrink, twist or rot like timber. It resists moisture, pests and environmental movement, which means less repair, less structural drift and better longevity. In WA’s climate—with termite risk, coastal zones and varying soil conditions—this matters.
2. Speed of Construction
Steel frames can be engineered off-site, prefabricated and delivered ready to install. This cuts on-site labour, trims waste and speeds up your schedule. At Steel Frames WA, we offer full manufacturing, supply and installation. Instead of framing from scratch on-site, specialised framing arrives and goes up quickly, letting interior tradies and subbies get to work straightaway.
3. Design Flexibility
Because steel can span further with less material, you gain more open space, fewer columns and greater freedom in layout. This is especially useful for open-plan homes, commercial builds or complex roof forms.
4. Fire and Pest Resistance
Steel is non-combustible and termite-proof (no chemical treatments required). It will not suffer from the problems timber does—warping, termite damage or rot. This gives peace of mind in high-risk zones and protects long-term asset value.
5. Sustainability
Steel is 100% recyclable. Many structural steel products contain up to 90% recycled content. When you reduce waste, site disruption and rework, you lower your environmental footprint.
When Structural Steel Needs Careful Assessment
While structural steel has many strengths, it is not one-size-fits-all. Here are some considerations:
- Initial cost – Steel framing may cost more up front than timber, depending on design complexity and site conditions. Long-term value often makes up for this.
- Thermal bridging – Steel conducts heat more than timber. For high-performance energy efficient homes, you will need careful insulation detailing.
- Corrosion in coastal zones – Near the coast or in high salt-air environments, specify galvanised, stainless or weathering steel to avoid corrosion.
- Acoustic performance – Some steel framed systems need extra detailing for high acoustic performance, especially in multi-storey or party-wall situations.
- Design lock-in – Because steel frames are factory-engineered, your design must be locked in early and drawings accurate. On-site changes can be more costly.
How to Assess Structural Steel for Your Build
Project scale and complexity – Steel shines in everything from simple single-storey homes to complex commercial builds, especially where spans, design freedom or prefabrication matter.
Time and site conditions – If you want to reduce site labour, handle remote delivery (WA’s remote regions) or manage site constraints, steel framing cuts risk and delays.
Budget and lifecycle cost – Compare not just upfront framing cost but maintenance, longevity, repair risk and value at resale.
Environmental and performance goals – If you are pursuing bushfire rating, termite resistance, energy efficiency or future-proofing, steel offers clear advantages.
Engineering and detailing – Ensure your design is engineered for WA conditions (soil types, bushfire zones, coastal zones). Choose suppliers with experience in WA.
Why Our WA-Based Experience Makes a Difference
At Steel Frames WA, we bring over 50 years of building expertise in Western Australia. Here is how that matters:
- We understand WA’s remote and regional logistics, so if your site is outside Perth, we can handle delivery and install.
- We know local soil, bushfire, termite and cyclone conditions—and frame accordingly.
- We provide full service: design, manufacture, supply and installation. That means fewer hand-offs, less risk and a smoother experience.
- Because we manufacture locally, we deliver precision, speed and quality—supporting your timeline and budget.
When you choose structural steel with us, you are not just buying steel sections. You are buying support, precision and an outcome built for WA conditions.
Final Thoughts
Structural steel is more than a building material—it is a strategic choice for strength, durability, speed and design flexibility. From its carefully controlled carbon content to its high strength-to-weight ratio, structural steel is engineered to perform in the toughest conditions.
Whether you are building a home, a commercial project or an industrial structure in Western Australia, understanding the grades, types and applications of structural steel helps you make smarter decisions.
We would be happy to help you assess your build—talk through the benefits, show how it stacks up for your site and budget, and provide a quote that aligns with your timeline. At Steel Frames WA, we are ready to help you build for the future.
