Contractor Guide
Steel vs Aluminum — Which Is Right for Your Project?
📅 May 2026
🕐 7 min read
🏢 MetalsDelivered.com
Steel and aluminum are both excellent construction materials — but they're not interchangeable. Pick the wrong one and you're either overpaying, overbuilding, or setting yourself up for a maintenance headache down the road.
This guide breaks down the real differences between steel and aluminum across every factor that matters to contractors — strength, weight, corrosion, cost, and weldability — so you can make the right call on your next project and get your quote in minutes.
3x
steel is heavier than aluminum by volume
3–4x
stronger tensile strength in structural steel
No rust
aluminum is naturally corrosion resistant
⚡ Steel vs Aluminum — The Quick Answer
Before diving into the details, here's the short version that covers 90% of contractor decisions:
▶ Choose Steel When...
You need maximum load-bearing strength
It's a primary structural member (beam, column, frame)
Budget is the priority material cost
The project is indoors or will be painted/coated
Your crew welds with standard equipment
▶ Choose Aluminum When...
Weight is a critical factor (roofing, facades, mobile structures)
The project is coastal, marine, or high-moisture
You need corrosion resistance without painting
Appearance and finish quality matter
Lower shipping weight reduces freight cost
💪 Strength & Load Capacity
This is where steel wins decisively for most structural applications. Structural steel (A36) has a tensile strength of 58–80 ksi. Aluminum alloys used in construction typically range from 30–45 ksi — roughly half to two-thirds the strength of structural steel.
Property
Structural Steel
Aluminum 6061
Yield Strength
36–50 ksi
35–40 ksi
Tensile Strength
58–80 ksi
42–45 ksi
Elastic Modulus
29,000 ksi
10,000 ksi
Hardness
Very High
Moderate
💡
Contractor takeaway: For primary structural members carrying real load — beams, columns, frames — steel is the standard. Aluminum's strength-to-weight ratio is impressive, but its lower stiffness (elastic modulus) means it deflects more under load, which is a problem in most structural applications.
⚖ Weight & Handling
This is where aluminum has a clear edge. Steel is roughly three times denser than aluminum — which has real implications for shipping cost, on-site handling, and the overall dead load of a structure.
490 lb
per cubic foot — structural steel
169 lb
per cubic foot — aluminum
For contractors, lighter material means lower freight cost per piece, easier handling without heavy equipment on site, and less dead load on a structure's foundation. In roofing, cladding, walkways, and canopy applications, this weight difference is often the deciding factor.
📦
Shipping tip: Aluminum's lighter weight can significantly cut freight costs on large orders — especially on long-haul deliveries. Always compare total delivered cost (material + freight) when choosing between the two materials for non-structural applications.
🌧 Corrosion Resistance
Aluminum wins here — and it's not close. Aluminum naturally forms a protective oxide layer when exposed to air, which prevents further corrosion without any coating. Steel, on the other hand, will rust without proper surface treatment.
Steel — Corrosion Profile
Rusts without coating or paint
Requires primer, paint, or galvanizing
Higher maintenance cost outdoors
Not ideal for coastal or marine environments untreated
Aluminum — Corrosion Profile
Naturally corrosion resistant
No painting required in most environments
Ideal for coastal, marine, high-moisture
Low lifetime maintenance cost
💳 Cost Comparison
Steel is generally cheaper per pound than aluminum — but the full cost picture is more nuanced. Here's how to think about it:
Cost Factor
Steel
Aluminum
Material price / lb
✔ Lower
▲ Higher
Freight cost
▲ Higher (heavier)
✔ Lower (lighter)
Surface treatment
▲ Required (paint/coat)
✔ Often not needed
Lifetime maintenance
▲ Higher outdoors
✔ Lower
Overall for structural
✔ More economical
♺ Higher upfront
💡
Bottom line on cost: Steel wins on raw material price. Aluminum can win on total project cost when you factor in lighter freight, zero painting, and lower long-term maintenance — especially in outdoor or coastal applications.
🔥 Weldability & Fabrication
Steel is significantly easier to weld with standard shop equipment. Aluminum requires more skill, specialized wire, and shielding gas — and its natural oxide layer must be removed before welding or you'll get a weak joint.
1
Steel welds with standard MIG, TIG, or stick equipment. Most field crews are comfortable with it. Preheating is required for thicker sections but is straightforward.
2
Aluminum requires TIG or MIG with aluminum wire and pure argon shielding gas. The natural oxide layer melts at a much higher temperature than the base metal — if not cleaned properly you'll get porosity and weak joints.
3
Fabrication: Aluminum is easier to cut, drill, and form due to its softness. Steel takes more force but holds tolerances better under load. For complex bending and forming, aluminum is generally more forgiving.
🏢 Best Uses in Construction
Steel — Common Uses
Building frames & structural columns
Wide flange beams & floor systems
Base plates, gussets & connections
Mezzanines & industrial platforms
Bridges & heavy infrastructure
HSS tubing for columns & trusses
Aluminum — Common Uses
Roofing panels & wall cladding
Architectural trim & curtain walls
Handrails, guardrails & walkways
Coastal & marine structures
Canopies, awnings & sunshades
Tread plate for flooring & ramps
✅ Which Should You Order? A Simple Decision Guide
Answer these questions to land on the right material fast:
1
Is it a primary load-bearing structural member?
Yes → Steel. Every time. Beams, columns, frames, and connections carrying real structural load should always be steel unless your engineer specifies otherwise.
2
Will it be exposed to moisture, salt air, or weather long term?
Yes → Aluminum is the lower-maintenance choice. Steel can work but will require painting, galvanizing, or regular maintenance to prevent rust.
3
Does weight significantly impact your project?
Yes → Consider aluminum. Roofing, cladding, walkways, and decorative structures often benefit from aluminum's lighter weight — less freight, easier handling, lower dead load.
4
Is budget your primary constraint?
Yes → Steel wins on raw material cost. For general structural work where corrosion isn't a concern, steel delivers the most value per dollar spent.
❓ Frequently Asked Questions
► Can I mix steel and aluminum in the same structure?
Yes, but with caution. Direct contact between steel and aluminum causes galvanic corrosion — especially in wet environments. Use isolation gaskets, neoprene pads, or coatings at all contact points. Always consult your engineer when mixing metals in structural connections.
► Is aluminum strong enough for structural use?
In lighter applications — yes. Aluminum is used in structural framing for aerospace, marine, and architectural applications. But for heavy load-bearing construction (columns, beams carrying floor loads, etc.), steel is almost always the right choice unless specifically engineered for aluminum.
► Does MetalsDelivered.com carry both steel and aluminum?
Yes. We stock structural steel (A36, A572, A992) and aluminum (6061-T6, 6063) in a wide range of shapes — bar, plate, sheet, angle, tube, and more. Both ship cut-to-size with no minimums and real-time pricing online.
► Which is easier to work with on site?
Steel is easier to weld with standard equipment. Aluminum is easier to cut, drill, and form. For field welding by a general crew, steel is more forgiving. For precision cutting and shaping, aluminum is less demanding on tooling.
► Not sure which material is right for your project?
Our team at MetalsDelivered.com fields material questions every day. Get a quote and tell us what you're building — we'll make sure you're ordering the right material in the right grade for the job.
Steel or Aluminum — We've Got Both.
Real-time pricing on structural steel and aluminum — cut to your spec, no minimums, delivered to your job site.
Not sure what to order? Tell us about your project and we'll help you spec it right.
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Materials We Carry
A36 Structural Steel
A572 Grade 50
A992 Wide Flange
6061-T6 Aluminum
6063 Aluminum
Aluminum Sheet
Steel Plate
HSS Tubing
MD
MetalsDelivered.com Editorial Team
Structural metal specialists — serving contractors nationwide
