The Materials & Components of a Steel Shipping Container

3 minute read
Aug 14, 2019
The Materials & Components of a Steel Shipping Container

In a previous blog post, we talked about the origins of shipping container names such as conex box, ISO container, and sea can. It’s been one of the most widely read posts on the Think Inside the Box® blog, so we thought it deserved a Part II. In this post we’re focusing on what shipping containers are made of: the materials and the components of these sturdy structures.

So… What are Shipping Containers Made of?

The corrugated walls, frame, cargo doors, and cross members of shipping containers are all made from Corten steel. Corten steel, also known as weathering steel, is the primary material in shipping containers. It’s distinguished from other types of steel in that it’s a group of steel alloys that were developed to eliminate the need for painting. Container manufactures use this material because it possesses the physical properties that make it weldable and rust resistant. In practice, rust-resistance means that should a piece of paint chip off of the steel, rust will form at the surface but go no deeper.

Components of a Shipping Container

Most every shipping container is manufactured to have these unique features:

Corner Castings

The reinforced corners of shipping containers are called corner castings. Corner castings have openings for twist lock connections that allow them to be connected to other containers or to anchor points. They’re also designed to be strong enough for crane rigging (to be lifted by rigging to a crane), even when fully loaded.

Twist Locks

Twist locks securely connect shipping containers to anchor points or to other containers. The end piece of the twist lock fits into the corner casting and then pivots to a locked position, usually via a lever.

Cross Members

Beams, or joists, called cross members support the shipping container floor. The space the cross members creates between the ground and the flooring prevents moisture from seeping into the container from underneath. Cross members are one of the reasons that many container structures such as ground-level offices don’t require a foundation. The cross members lift the structures away from the ground and mitigate the risk of damage caused by natural elements.

Forklift Pockets

Standard 20-foot containers and many 40-foot containers come with two openings along the bottom edge of the structures, called forklift pockets. As their name implies, forklift pockets are reinforced slots designed to accommodate forklift tines. Forklifts can insert the tines into the pockets in order to lift and move the structures. Please note that some shipping container modifications add enough weight to the structure that it makes lifting by forklift inadvisable, especially with modified 40-foot shipping containers.

Cargo Doors

A storage container’s cargo doors are the two steel doors most often found at one end of the container (though some shipping containers have cargo doors on both ends, or even have cargo door side walls). Cargo doors were designed to prevent theft and weather intrusion on long voyages and offer formidable security for the assets contained in them. The door’s locking mechanism may be unfamiliar to new container users, so be sure to check out our video on how to open shipping container cargo doors.

CSC Plate

CSC is an acronym used to indicate The International Convention for Safe Containers. This convention is a set of standards for shipping container design intended to prevent structural failure and protect human life. For example, shipping containers loaded with tens of thousands of pounds of cargo are often stacked several units high, and a collapse in a port or at sea could be catastrophic to employees working below. The CSC plate affixed to the shipping container certifies a qualified inspector has examined that container and confirmed that it can safely carry cargo.

Falcon Plate

Similar to a CSC plate, the Falcon Plate is specific to modified containers manufactured by Falcon Structures and indicates that the container has met Falcon's own standards for high-quality and safe structures.

Marine-Grade Plywood Flooring

Most shipping containers come with marine-grade plywood flooring. The flooring is infused with a small amount of insecticides to prevent six-legged stowaways from joining the container’s voyage. These insecticides do not aerosolize and are only a risk to hungry bugs, not to the people who come in contact with the flooring. We even kept the original plywood flooring in the container-based Falcon Structures office.

Bamboo Flooring

The number of containers that use bamboo flooring instead of marine plywood has been steadily increasing, thanks to lower costs and greater availability. Bamboo is mildew resistant and very durable, making it a good option when aesthetics is important, such as in shipping containers modified for living spaces. You’ll know that your container has bamboo flooring if you see a woven pattern beneath your feet!

As you can see, shipping containers are relatively simple structures, making them the ideal base for modifications that can turn them into highly functional spaces for living, working and storage. Not only are they flexible, they’re easy to install and can be customized with lighting, doors/windows, climate control, and more. As you consider options for your project, don’t hesitate to reach out and ask us for additional information. You can reach us at 877-704-0177 or

Ultimate Guide to Modified Shipping Containers

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