Steel vs. Aluminum Carports: Which Lasts?
Buying Guide ·
Steel and aluminum are the two metals most carport frames are built from, and they behave very differently under load. The short version: aluminum resists corrosion on its own and is lighter to handle, but steel is far stronger and stiffer — which is what matters when the structure has to carry a roof, shrug off wind, and hold up snow.
The short answer
For a permanent, load-bearing carport, steel wins on structural performance. Steel has roughly three times the stiffness of aluminum and a much higher yield strength, so a steel frame resists bending, sway, and collapse under heavy wind and snow that would overload a comparable aluminum frame. Aluminum earns its place in lightweight, portable, and marine-adjacent applications where its natural corrosion resistance and low weight are the priority — think pop-up canopies and boat-cover frames, not a structure you permit and build for decades.
Strength and structural load
This is the category that decides most carport decisions. Structural steel has both a higher yield strength and a much higher modulus of elasticity (stiffness) than aluminum — steel is about three times as stiff for the same cross-section. In practical terms, a steel member of a given size deflects far less under the same load, so a steel carport can span wider bays and carry heavier roof and snow loads without the frame flexing. Aluminum is more elastic; it bends and springs more, which is fine for a lightweight cover but a liability once you are anchoring a real roof against a storm.
Steel is heavier — roughly 2.9 times the density of aluminum — and that weight is part of the trade. A heavier frame is more work to ship and raise, but it is also what gives a steel structure its rigidity and anchoring mass. Our steel carport kits are built from commercial-grade S350 structural steel for exactly this reason: to hold their rated loads without oversizing every member.
Corrosion resistance
This is aluminum's home turf. Aluminum forms a thin, self-healing oxide layer the moment it meets air, and because it contains no iron, it cannot rust. Left bare outdoors, aluminum holds up well, which is why it is popular near saltwater and in humid climates.
Bare steel, by contrast, will rust — so the entire question for a steel carport is the coating, not the base metal. Modern metallic coatings close that gap almost entirely. Our frames use a ZAM zinc-aluminum-magnesium coating, a self-healing alloy layer engineered for long-term corrosion resistance even where the surface is cut or scratched. Properly coated steel competes directly with aluminum on longevity while keeping steel's structural advantage. The takeaway: judge a steel carport by its coating system, and judge aluminum on the understanding that its strength ceiling is lower to begin with.
Wind and snow ratings
Because ratings follow strength and stiffness, this is where the two materials separate most clearly. A properly engineered steel frame can be rated for severe wind and heavy snow; lightweight aluminum carports are typically rated for far milder conditions and are often sold as light-duty or seasonal shelters. If you live where hurricanes, straight-line winds, or real snow load are on the table, the structural margin of steel is not a luxury — it is the point.
Our carport frames are engineered to withstand 185 MPH winds and 60 PSF snow loads, and ship with engineer-stamped, permit-ready drawings so those numbers are documented for your building department rather than assumed.
Cost and value
Per pound, aluminum is often the pricier raw material, but it is also lighter, so material cost alone is a poor guide. The more useful comparison is cost per unit of strength: to reach the same structural capacity, an aluminum frame needs larger or thicker members, which erodes its price advantage. For a permanent carport that has to hit real load ratings, steel generally delivers more structure per dollar. Add the fact that a coated steel frame can last decades with minimal maintenance, and steel is usually the better long-run value for a fixed structure.
Steel vs. aluminum at a glance
| Factor | Steel | Aluminum |
|---|---|---|
| Strength | Higher yield strength; carries heavy loads | Lower strength; suited to light loads |
| Stiffness | ~3× stiffer — resists flex and sway | More elastic; bends and springs more |
| Corrosion | Rusts if bare; excellent once coated (ZAM / galvanized) | Naturally rust-proof oxide layer |
| Weight | Heavier — more anchoring mass, more to ship | Light and easy to handle |
| Wind / snow rating | Can be engineered for severe wind and snow | Typically light-duty or seasonal |
| Cost per strength | More structure per dollar for load-bearing use | Price climbs as members are upsized |
| Best for | Permanent, high-load, permitted carports | Portable, lightweight, marine covers |
Which should you choose?
Choose aluminum when weight and bare-metal corrosion resistance outrank raw strength — a portable cover, a boat frame, or a small light-duty canopy. Choose steel when the carport is a permanent structure that must carry a roof and meet wind and snow requirements, which describes almost every fixed carport, garage-alternative, or RV and equipment shelter.
- Need it to hold real snow or survive high wind? Steel, with a documented rating.
- Worried about rust? Ask about the coating system — a ZAM or galvanized finish is what makes steel last.
- Want something you can pick up and move seasonally? Aluminum's light weight is the advantage.