Cross members
Steel joists running under the floor, holding it up and holding it clear of the ground so damp cannot soak up into the wood from underneath. Falcon Structures, read 2026-08-31.
Containers
How a shipping container is made
Flat corten steel sheet becomes a corrugated wall panel, the panels get welded into a box around eight cast corner castings, a treated wood floor goes in over steel cross members, and the finished unit is painted and plated before it ever carries cargo. Most of that work happens in China. Sources read 2026-08-31, cited below.
Sources cited and datedNo price inventedRouted to a person for a quote
Welded, not bolted
A container is one continuous steel weldment. Nothing structural on it is held together with fasteners.
The build starts as flat steel, corrugated for stiffness
Falcon Structures, a container fabricator, sets out what the container itself is built from: the frame, the corrugated wall panels, the cargo doors and the cross members are all corten steel, also called weathering steel. Read 2026-08-31.
Corrugating a wall panel — ribbing it rather than leaving it flat — is what lets a sheet of steel a few millimeters thick carry the load of a fully packed box beneath it and several more boxes stacked on top. Corten's own rust behavior, and why resistance is not the same thing as rustproof, is covered on this site's own container rust guide; here the steel matters only as the material the build starts from.
What gets welded, and why the corners carry everything
“Cast steel, welded to the corner posts.” Falcon Structures, What Are Shipping Containers Made Of? (Materials, Parts & Specs), falconstructures.com, read 2026-08-31, describing the container's corner castings
That is the whole job of a corner casting: eight cast-steel fittings, one at each corner of the box, welded on rather than bolted. Every load a container carries passes through them. A crane's spreader lowers steel pins into the castings and twists them to lock on before lifting a loaded box, and a stack of containers at a terminal or aboard a ship rests corner-to-corner through the same fittings, sending the weight of everything above straight down through that one welded joint.
Forklift pockets
Reinforced steel slots built into the base rails, letting an empty or loaded container be picked up and moved without a crane on hand. Falcon Structures, read 2026-08-31.
The corner fitting standard
ISO 1161 sets the dimensions and the strength the castings have to meet. The Bureau International des Containers puts it plainly: as every load a container carries passes through the corner fittings, that standard is central to the whole structure.
The floor, the doors, and what makes a unit sellable
The floor is the one major part of a general-purpose container that is not steel. Falcon Structures names marine-grade plywood, treated with insecticide, as the standard, with bamboo flooring increasingly used as an alternative — chosen for standing up to moisture and mildew about as well, and for coming from a fast-growing stand rather than timber cut specifically for the purpose. Read 2026-08-31.
The cargo doors are built from the same corten steel as the walls and hung to close and seal an opening wide enough for a forklift to drive straight through. The last step before a finished container is sellable at all is a CSC plate, riveted near the doors, carrying the unit's stacking and lifting ratings and certifying it has actually been tested to those numbers rather than just built to a drawing. Falcon Structures, read 2026-08-31.
Where the boxes actually get built
“Based in Shenzhen, China, CIMC is the world's largest shipping container manufacturer.” Container xChange, Top 10 Shipping Container Manufacturers Globally, container-xchange.com, read 2026-08-31
CIMC is one line item on a longer list, and most of the rest of that list is Chinese too: DFIC in Shanghai and CXIC in Jiangsu are named alongside CIMC among the largest producers, and Singamas, a Hong Kong-based manufacturer, rounds out the group. A smaller share of new-build capacity sits outside greater China — the same ranking names manufacturers in Denmark, Singapore, India, the United States and the United Kingdom — but a new dry general-purpose container bought today was, overwhelmingly, built in a Chinese factory. Read 2026-08-31.
That concentration is also why the dimensions match no matter who built the box. ISO 668 sets the classification, external dimensions and ratings for what the industry calls a Series 1 freight container, so a 20-foot unit off one factory floor stacks cleanly under a 40-foot unit off another. The current edition is ISO 668:2020, with an amendment published February 2022, per the Bureau International des Containers, read 2026-08-31.
Where these figures come from
- Falcon Structures, What Are Shipping Containers Made Of? (Materials, Parts & Specs) — the corten steel components, corner casting construction, cross members, forklift pockets, floor materials and the CSC plate. Read 2026-08-31.
- Container xChange, Top 10 Shipping Container Manufacturers Globally — the named manufacturers and where they are based. Read 2026-08-31.
- Bureau International des Containers, The Key ISO Standards — what ISO 668 and ISO 1161 each cover, and their current edition dates. Read 2026-08-31.
Fabricators vary their own process in small ways, and manufacturer rankings shift year to year. Treat everything above as three sources read on the date shown, and confirm build specifics with whoever is quoting a specific unit.
If the job needs an actual container quote
SMKlog's checkout prices United States domestic parcel labels; it does not build, sell or price a shipping container. A freshly manufactured unit, a used one being resold, or a full container load headed overseas all route through freight review instead, where a person works from the size and route you actually have.
Container build questions
How is a shipping container built, start to finish?
Flat steel sheet is corrugated into wall panels for stiffness, then the panels, corner posts, corner castings, cross members and roof are welded into one hollow steel box. A treated wood or bamboo floor goes in over the cross members, the corten steel doors are hung and sealed, and the finished unit is primed and painted before a CSC plate is fixed to it certifying it fit to stack and lift.
What steel is a shipping container built from, and is it special?
Corten steel, also called weathering steel, used for the frame, the corrugated wall panels, the cargo doors and the cross members. It is chosen because it holds up to years of outdoor and ocean handling, not because it stops rust outright — the choice of steel for the build is a separate question from whether the finished container rusts.
How are the corner castings attached, and why do they matter?
Falcon Structures describes them as cast steel, welded to the corner posts. Every load the container carries passes through those eight fittings: a crane's twist-locks grip them to lift a loaded box, and a stack of containers rests corner-to-corner through them, which is why their dimensions and strength are set by their own ISO standard, ISO 1161.
What is the floor of a shipping container made of?
Marine-grade plywood treated with insecticide is the standard, resting on steel cross members that hold it clear of the ground. Bamboo flooring is an increasingly common alternative, chosen for holding up to moisture and mildew and for coming from a fast-renewing stand rather than old-growth timber.
Where are most new shipping containers built today?
Overwhelmingly in greater China. Container xChange's own ranking of manufacturers names CIMC, headquartered in Shenzhen, as the world's largest shipping container manufacturer, and two more of the companies on that same list, DFIC and CXIC, are also mainland China-based, with Singamas rounding out the group from Hong Kong. A smaller share of new-build capacity sits in Denmark, Singapore, India, the United States and the United Kingdom.
Does SMKlog build, sell or price shipping containers?
No. SMKlog's checkout prices United States domestic parcel labels. A container purchase or move goes through freight review, where a person prices it against the actual size, condition and route.