The development of the shipping container industry threw up some interesting design problems as its own success then began the need of variations in shipping container construction. Customers had different needs and its surprising that the industry managed to keep within its standard design structure with such needs. At the same time more modifications to the standards had to be added as new problems developed that hadn’t been seen with such things as the corner standard fittings you see on the shipping containers, but nobody had assessed maximum payloads and containers began to fail because they hadn’t been tested to high stress levels and needs of customers demands. As these failings became apparent the International Standards Organisation was swift to step up the specifications on the standards and the quality and strength of shipping containers improved.
The next issue involved railroad cars as there needed to be shipping container reinforcements on the end plates as the containers had extra pressure added when the railroad cars hitched and unhitched costing around an extra $100 per shipping container.
The next issue was standardising the lengths of units to fit into all shipping situations and this seen the rise of five initial standard shipping containers develop :-
- 20 ft (6.1m)
- 40 ft (12.2m)
- 45 ft (13.7m)
- 48 ft (14.6m)
- 53 ft (16.2m)
The matrix of shipping containers were designed so that they would fit into most fitting needs and being able to interlock the different sizes within ships without difficulty. The U.S. prefers the larger shipping containers while Europe prefers 40ft containers. Adding to this was the weight restrictions to keep the shipping containers manageable but also within restrictions such as road limits for freight this seen the following standard shipping container weights develop :-
- 20 foot: 52,910 lbs/24,000 kg
- 40 foot: 67,200 lbs/30,480 kg
- 45 foot: 67,200 lbs/30,480 kg
- The net load totals are:
- 20 foot: 48,060 lbs/21,600 kg
- 40 foot: 58,820 lbs/26,500 kg
- 45 foot: 56,620 lbs/25,680 kg
The development of the shipping container has seen two materials mainly in use Aluminium and Steel. Most common being steel as it handles the bashing of shipping container needs as well as still functionally light and a cheap material. Aluminium is a more expensive solution but doesn’t suffer with the obvious rust problems that steel does. In recent years though Corten steel has seen its entry onto the market place which is rust and mould proof making it the most practical solution.
When most people think shipping container they are thinking a solid steel box used to transport goods around the world. A unit that is able to rust easily and overheats in the sun at the same time cold when temperatures drop.
In reality you have this on the left, a blank canvas for modular construction the box like shape gives you a starting point that has many alternatives in its construction and not only that its easy to work with. The skill set needed for self building is reduced drastically down to weights and possibilities, design is reduced down to budgets and creativity. So when you think container think of the drawing as its the basis of modular construction that is sustainable and often from re-cycled units allowing a reduction in waste at the same time putting it to good use. Also using the shape from the drawing takes away a lot of the boundaries people set in their mind and allows the thoughts to flow on how to attach multiple units together to form up a home. The important thing to remember though is the strength comes from the outer frame the wider parts shown on this side of the drawing.
The 20ft Shipping Container is no longer the main size used for international shipping but its still utilized as one of the standard ISO sizes. When talking about Twenty Foot Equivalent Unit (TEU) its often how the standard sizes are discussed in the shipping industry. The size may vary in length but will still be recognised as 1 TEU the only constant being the 8ft width as height can go from 4’ 3” to a high cube of 9’6” and even the volume space would not make a difference to the terminology of it still being 1 TEU. Once it gets over 40ft in length however it suddenly becomes 2 TEU in size part of the imperial measurement system. Odd thing is with a container being of 40ft or more it becomes rated as a Fourty Equivalent Units (FEU). May seem a bit odd but it came down to War and a standard “estimated” size had to be implemented because there were too many variables on things being moved by the military that one size fits all simply didn’t work but getting a system as close to was needed and its why the FEU and TEU exist today.
Gross mass maximum rating on a 20ft shipping container is 24,000kg and a 40ft container is 30,480kg regardless of height.]
Payload Maximum weights are 21,600kg for 20ft and 26,500 for the 40ft.
The 20ft shipping container was the standard unit size used by Matson and other shipping companies as it was convenient size for goods shipped between the West coast of the United States and Hawaii. More importantly they sat inside the converted World War II C-3 cargo ships Matson used for many years. It was however in 1957 that Matson then decided to start using containers at 25ft as this maximised his transportation potential for his purposes. His freighters could then transport the units six high inside the cargo holds and on the top deck of the freighters. For trucking purposes a 20ft shipping container was too short as loading two of them onto a bed often would break road weight limitations meaning the trucks could only haul one 20ft at a time. The optimal size for a single bed truck is 24 – 27ft in length.
In todays world we see shipping containers of up to 48 and 53 feet in length which are popular for international shipping as loading time for 20ft takes just as long as a larger shipping container but obviously takes twice as long to load a ship, time is money and why many 20ft shipping containers are being abandoned for the larger units as its not economically viable to use in comparison to the larger containers or in fact the improved road structures we see today that allow easier freight transportation.
20ft shipping containers are still available and are even still being manufactured, yet its the bigger shipping containers that are mainly used due to the reasons above.
These car showrooms are a practical example of how a shipping container module can be used. I have also worked with a company in the UK previously that use the outer steel frames you see here that form an open sided shell that slot walls drop into. This is probably based on the same technology but still using the shipping container size and weights for transportation. A small 7.5 ton truck with attached crane can move these and deliver one at a time. Making it not only cost affective for construction but also transportation.
With the initial assessment on home designs done with shipping containers as well as assessing the best methods of either interior or exterior cladding done. I then thought but how many people actually know the dimensions of a shipping container? Because no point ordering one if it won’t fit in the place your looking to put it.. so here is the information on internal,external and weight limits of a 20ft shipping container.
20 Foot Container Specifications:
External Dimensions Internal Dimensions Operating Weights (lb)
Length: 20′ Length: 19′-4″ Max Gross: 52,910
Width: 8′ Width: 7′-8″ Max Payload: 47,895
Height: 8′-6″ Height: 7′-9″ Tare: 5,015
Internal Capacity: 1,166 Cubic Feet