Shipping Container Design
Developed by an American trucker, Malcolm McLean, who had one of the largest truck transportation business in the U.S. in the 1940s and 50s, shipping containers revolutionized the international transport industry.
While McLean’s original containers were standardized in terms of size (all 35-foot), extremely strong, stackable, and lockable, they were relatively rudimentary. But the industry developed fast, and in 1968 the first International Organization for Standardization (ISO) standards were introduced. These defined the terminology, dimensions, and ratings of freight containers as well as the way they should be identified.
As a result of these original standards, sizes for shipping containers were regulated. All general-purpose (GP) containers have a width of just under 2.5 m or 8 ft:
- 20 foot (6 m) containers that measure 20 ft x 8 ft (6.058 m x 2.438 m) and are 8.5 ft (2.591 m) high. These are also available as high cubes that are 9.5 ft (2.896 m) high.
- 40-foot (12 m) containers that measure 40 ft x 8 ft (12.192 m x 2.438 m) and are 8.5 ft (2.591 m) high. High cubes are also available.
- 10-foot (3 m) containers that measure 10 ft x 8 ft (2.991 m x 2.438 m) and are 8.5 ft (2.591 m) high
Today there are different types of containers designed for different purposes, including those intended for transporting dry freight across the oceans, and reefers that are designed for storing and transporting items that need to be refrigerated. There are also specialized shipping containers that are manufactured for the transportation of oversized or unconventional cargo. However, GP containers are the norm for architectural conversion products.
ISO 1496-1 : 1990 (E), Series 1 freight containers – Specification and testing – Part 1: General cargo containers for general purposes details how GP containers transported by sea, road, or rail should be manufactured. In addition to dimensions, the standards specify tolerances as well as specifications for every part of the container: corner fittings, the end and the side structures, the walls and door openings, and the corner fittings which are very important for easy stacking.
Other vital requirements relate to strength, loads and loadings, locking devices fitted for container roofs (or tops), as well as the securing systems that are suitable for doors. Weatherproof covers are also included in the specifications. The testing procedures used to ensure that freight containers have been correctly manufactured are included in the same ISO. They include tests for:
- stacking containers that are fully loaded
- lifting containers from the four corner fittings at the top of the box
- lifting containers from the four corner fittings at the bottom of the box
An additional 10 test procedures are provided. These enable manufacturers to test the strength of each part of the container – the end and side walls, the floor, and the roof – as well as its longitudinal restraint and transverse and longitudinal rigidity. There is also a test for checking whether it is weatherproof and for the efficiency of lifting it from fork-lift pockets and the base where grappler arms are positioned (if these are fitted).
While these standards were devised to ensure that shipping containers are strong and secure for transportation and storage before, during, and after transportation, they also provide peace of mind for those opting for a container conversion or construction project. When choosing used containers for new construction projects, it is important to assess their structural integrity, which is another role that an engineer might play. Old containers may be dented and rusted after being transported over the ocean. Also, they are sometimes coated with lead-based paints or other products to protect the metal surfaces from moisture and from salt in the seawater. These must be covered for safety reasons. However, it is common for architects to design container structures with new floors, ceilings, and walls, both internal and external. This effectively covers dings and dents and also provides an easy means to install essential insulation. That said, it is not unusual for new shipping containers to be specified for projects.
While basic plumbing and power are relatively easy to install, heating and cooling systems often present a major challenge in this environment, which is why an increasing number of architects like to team up with MEP engineers for container construction projects. Another factor is that even though containers themselves are manufactured in accordance with strict international (ISO) standards, there are also codes and regulations that must be followed when containers are converted for alternative use. These usually depend on local regulations that vary from area to area, city to city, and even country to country. Some places may not even have regulations, which might translate to a lack of control or, on the other hand, to a blanket prohibition. For instance, while codes for so-called pre-fab structures might not be strict, in many places the regulations relating to container construction could be stringent because this type of construction is largely untested.
It is essential to ascertain ground rules before going ahead with shipping container construction.