Quick answer: Shipping containers are made from Corten steel, a weathering steel that resists corrosion. Factories cut steel coil into sheets, corrugate the sheets into wall and roof panels, and weld them to a heavy steel frame with corner castings. Next comes a marine-grade plywood floor. The container is then sandblasted, primed, painted, and fitted with doors and seals. Before it can enter international shipping, it has to pass inspection and receive a CSC safety plate. Most new containers are built in China.
That’s the short version. Below, we walk through each step and explain why it matters if you’re buying, renting, or customizing a container.
What Are Shipping Containers Made Of?
Shipping containers are made of Corten steel (also called weathering steel), with marine-grade plywood floors and rubber door gaskets. Each material is chosen to survive years of salt spray, heavy stacking, and rough handling at sea.
| Component | Material | Why it’s used |
| Walls & roof | Corrugated Corten steel | Strength-to-weight ratio, corrosion resistance |
| Frame (rails, posts, cross members) | Heavier-gauge structural steel | Carries the load when containers are stacked and lifted |
| Corner castings | Cast steel | Lifting, stacking, and twist-lock connection points |
| Floor | Marine-grade hardwood plywood (often treated) | Handles forklift traffic and heavy cargo |
| Doors | Corten steel with locking bars | Security and weather sealing |
| Seals | Rubber gaskets | Keep water and pests out |
Why Corten Steel?
When Corten steel is exposed to the weather, it forms a stable rust-colored layer called a patina. That layer slows further corrosion. On a container, the steel is also primed and painted, so the patina works as a backup layer of protection. This is one reason a well-maintained container can last for decades.
What this means for modifications: Corten is harder to cut and weld than mild steel. When we add doors, windows, or vents, we frame every opening with new steel and seal and paint the cut edges. That keeps the container’s weather resistance intact.
How Are Shipping Containers Made? Step by Step
Here’s how a standard dry container moves through a factory:
1. Steel Coil Is Cut Into Sheets
Large rolls of Corten steel are unrolled, flattened, and cut into sheets sized for walls, the roof, and the floor framing.
2. Sheets Are Corrugated
The sheets run through a press that forms the familiar trapezoid ridges. Corrugation makes thin steel much stiffer. It’s why container walls can handle stacking and side loads without being especially thick.
3. The Base Frame Is Built
Workers weld the bottom side rails, cross members, and forklift pockets (on some sizes) into the floor frame. This frame carries the cargo weight.
4. Walls, Ends, and Roof Are Welded On
The corrugated side panels, front wall, and roof are welded to the base frame, the corner posts, and the corner castings. Much of this welding is automated, with workers handling the finishing passes.
5. Sandblasting, Priming, and Painting
The container is sandblasted to clean the steel. It then gets a zinc-rich primer, followed by layers of industrial marine paint. This step does more for long-term rust protection than any other.
6. Flooring Is Installed
Marine-grade plywood floor panels are laid over the cross members and bolted down. Floor wood is usually treated so it meets agricultural import rules for international shipping.
7. Doors, Hardware, and Seals Are Fitted
Cargo doors, hinges, locking bars, and rubber gaskets go on last. The underside gets an undercoating for extra protection.
8. Inspection and Certification
Each container is checked for watertightness and structural soundness. It receives a CSC (Convention for Safe Containers) safety approval plate and a unique ISO 6346 identification code that tracks the box through its working life.
How Long Does It Take to Make a Shipping Container?
On a modern production line, one standard container can be built in a matter of hours. Large factories produce hundreds of units per day. The high volume is a big part of why containers are affordable building blocks for storage and structures.
Where Are Shipping Containers Made?
Most new shipping containers are made in China. A small number of large manufacturers produce the majority of the world’s dry containers, close to the ports where new boxes are loaded and put into service. Containers are built to ISO standards, so a container from any certified factory has the same dimensions and corner fittings. That means any certified container fits the same ships, trucks, and cranes worldwide.
For buyers on the West Coast, this matters. Containers arrive at California ports carrying imported goods, and many are later retired from shipping service and sold as used units. That steady supply keeps used and one-trip containers available in our region.
New vs. Used: How Manufacturing Affects What You Buy
Every container starts out built the same way. What changes is how it has been used since:
- New / one-trip containers have made a single voyage. The paint is fresh, the floor is clean, and the doors operate smoothly. They’re a good fit for homes, offices, and customer-facing builds. See new containers
- Used containers have spent years in shipping service. They’re still structurally sound and wind- and water-tight when properly graded, and they cost less. That makes them a great fit for storage. See used containers
From Factory Box to Custom Build
A container leaves the factory as a strong steel box. Turning it into an office, tack room, cabin, or restaurant means cutting into a structure that was engineered as a single unit. Factory construction affects modifications in a few ways:
- Corner posts and frame rails carry the load. Large openings need added steel framing to restore strength.
- Corrugated walls stiffen the box. Removing long sections of wall changes how the container handles weight.
- Factory floors are chemically treated for international shipping. For living or working spaces, they’re often covered or replaced.
At Container Stop, we design and modify containers with real-world regulations in mind. We plan openings, framing, and finishes so your container is ready for the use you have in mind. We don’t handle permits; that part stays with you and your local building department. Our team builds every container with code requirements in view, so your project starts on solid footing.
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Ready to Put a Container to Work?
Whether you need secure storage or a fully customized structure, Container Stop sells, rents, customizes, and delivers 10′, 20′, and 40′ containers across California, Oregon, Nevada, and Arizona.
Request a quote or call 1-800-674-9343.
Frequently Asked Questions
What are shipping containers made out of?
Shipping containers are made out of Corten steel, a corrosion-resistant weathering steel, with marine-grade plywood floors, steel doors, and rubber seals.
How is a shipping container made?
A shipping container is made by cutting and corrugating Corten steel sheets and welding them to a steel base frame and corner castings. The container is then sandblasted, primed, and painted, and the floor, doors, and seals are installed. It goes through a final inspection before certification.
Are shipping containers made of stainless steel or aluminum?
Standard dry containers are made of Corten steel, not stainless steel. Some refrigerated (reefer) containers use aluminum or stainless interiors, but the outer structure of most containers is weathering steel.
Where are most shipping containers manufactured?
Most shipping containers are manufactured in China, by a handful of large producers that supply global shipping lines.
Can you cut into a shipping container without weakening it?
Yes, if it’s done correctly. Every opening needs to be reinforced with steel framing to replace the strength that’s lost. That’s why professional modification is the safer choice for doors, windows, and multi-container builds.