Steel containers for shipping are manufactured in a small number of standard sizes for certain specific purposes. While standard sizes for these ubiquitous mobile containers range from 10ft to 45ft, the most commonly used sizes are the 20ft container and the 40ft container.

The ISO standards specify the overall dimensions of steel containers as well minimum internal dimensions and the size of door openings. The sizes of any general purpose (GP) 20ft and 40ft container should be:

• 20ft container:
  • Overall dimensions: Length 20 feet (6.058 m), width 8 feet (2.438 m), height 8 feet 6 inches (2.591 m).
  • Minimum internal dimensions: Length 19 feet 41/8 inches (5.898 m), width 7 feet 8½ inches (2.350 m), height 7 feet 8½ inches (2.350 m).
  • Minimum door opening dimensions: Width 7 feet 8 inches (2.337 m), height 7 feet 5 inches (2.261 m).
• 40ft container:
  • Overall dimensions: Length 40 feet (12.192 m), width 8 feet (2.438 m), 8 feet 6 inches (2.591 m).
  • Minimum internal dimensions: Length 39 feet 5½ inches (12.029 m), width 7 feet 8½ inches (2.350 m), height 7 feet 8½ inches (2.350 m).
  • Minimum door opening dimensions: Width 7 feet 8 inches (2.337 m), height 7 feet 5 inches (2.261 m).

Both the 20ft and 40ft container are also available as high cube (HC) GP containers. These are the same length as ordinary GP steel containers but they are higher. Both the 20HC and 40HC mobile containers are 9 feet 6 inches (2.896 m) high.

Why Choose a 40ft Container?

Generally, 40-foot dry freight, GP shipping containers are made completely of welded steel except for the floors which are usually made of load-bearing marine-grade plywood, although some do have steel floors. The thick, steel double doors at one end (like those of 20-foot dry freight mobile containers) are weather-sealed and absolutely secure. The mobile containers themselves are freestanding and totally self-contained, and may be used for shipping, for storage, and converted shipping containers can even be used for accommodation.

GP mobile containers are used for dry freight of all kinds, from rocks to food, clothing, and even vehicles. Obviously, you will choose a container that provides sufficient space (in terms of volume) for the goods you need to transport, and a 40ft container has double the capacity to a 20ft container. But another element that must be considered is payload. This is generally 20 tons. If mobile containers are overloaded in terms of their carrying capacity (measured in weight) that provides revenue for the carrier, there will be a “heavy weight surcharge”.

For this reason, 20-foot containers are commonly used to carry heavy goods, like iron ore or rock, while a larger 40ft container, with the same payload, will be used to transport lighter products. And of course, you will be able to squeeze even more into a 40ft high cube container. These are the largest size steel containers currently used by shipping lines on a routine basis.

Almar has storage and dry freight and mobile containers as well as converted containers. Contact us for container rental prices.

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Stackable shipping containers have been used to transport cargo for more than half a century, and nothing much has changed in terms of their construction. Most are made of corrugated steel and incorporate floors made from strong planking or plywood. But while steel is not the only material used for shipping containers, steel containers are the most common type for various reasons including security, mobility, accessibility, and lifespan.

Since 1969, steel containers have been standardized in terms of the material used for construction and their size, as well as the patented design of the corner posts incorporated in the design of these mobile containers.

Standardization of steel containers used for overland and ocean shipping is in accordance with the Swiss-based International Organization for Standardization (ISO) that develops and publishes international standards on just about everything.

ISO Standards for Steel Containers

ISO standards specify the type of steel containers should be made from. Essentially, it is a “weathering steel” that is resistant to corrosion and commonly referred to as Cor-ten steel. It is the same type of steel used in the many industries that utilize steel sections like bridges, facades and building panels that are left exposed to the elements.

When it comes to size, ISO standards specify both the internal and external dimensions of steel containers, which is why standard size lengths are the same worldwide, the most common being 10 ft, 20 ft, and 40 ft. Most are 8 ft wide, and the height of steel containers ranges from 4 ft to 9 ft 6 ins though most are 8 ft 6 ins high.

But containers aren’t only made from steel, some are made from aluminium and sometimes stainless steel too – usually a combination of the two metals.

Mobile Containers Made of Aluminium

Significantly different to steel containers, shipping containers are also made from aluminium according to ISO specifications.

For some years, both steel and aluminium were used for mobile containers that would carry dry cargo. But steel was stronger and therefore became the preferred material. At the same time, because refrigerated products are generally a lot lighter than dry cargo, a combination of aluminium and stainless steel continued to be used for refrigerated shipping containers. Generally, the walls of these aluminium containers are considerably thinner than those of steel containers, and their thermal insulation is increased by the use of other materials on the inside of their walls.

Steel containers and those made of aluminium cannot be used interchangeably. Apart from anything else, the latter isn’t constructed for stacking, and they are generally used domestically, within countries of origin, rather than for shipping cargo across the sea or across continents.

Of course, refrigerated containers aren’t only made of aluminium. Today reefers (the term for refrigerated containers) are commonly made from steel.

Steel Containers from Almar

Almar Container group specialises in steel shipping containers and has the full range of sizes. Our mobile containers are suitable for dry and refrigerated freight, depending on your needs. They may also be used for storage. Contact us to discuss your needs. We are ready to help.

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