We see wavy metal walls and roofs on industrial, agricultural, and homes all around the world. There are several good reasons why the metal walls and roofs of shipping containers are corrugated. Let’s check out the history of the corrugated metal, structural qualities, and then the pros and cons of corrugation.
Since the 1820’s, metal has been corrugated and used in building construction because it is strong while lightweight, corrosion resistant, easy to install by semi-skilled workers, and easy to be transported.
Surprising, there are a lot of benefits to using corrugated metal in the construction of shipping containers. These same great attributes carries on into the benefits of using shipping containers in our home designs.
Here are Some Reasons that Corrugated Metal is Used in Shipping Containers
Back in the 1820’s, London Dock Company needed a better material to use when manufacturing items of their trade. So, a British engineer/architect who worked for the company invented corrugated metal. His name was Henry Palmer.
On a side note, Henry Palmer was also the inventor of the monorail.
The metal that was used during that time was wrought iron. So, Henry Palmer called his new corrugated metal invention “CGI,” short for “Corrugated wrouGht Iron.” I know, it is a little stretch to get CGI out of that, but we can’t change history.
Since the invention of the corrugated metal by Mr. Palmer, we now make corrugated metal with other metals like galvanized or painted steel, and anodized aluminum.
Shipping containers are built with painted steel corrugated metal.
Structural Qualities of Corrugated Metal
To illustrate how corrugated metal is stronger than flat sheet metal, get out a sheet of paper. Hold the paper flat on one end.
The paper flops down because there is not enough support to keep it from bending. This is the same in structural beam design. If a beam is spanning across a long direction and is not very thick or deep, then it will deflect and sag in the middle.
So, to keep the sheet of paper or sheet of steel from bending, it can be made thicker and deeper.
The thickness of the metal sides of a shipping container is 1.6 to 2 mm. That’s about 5/64”which is not very thick, but when it is corrugated, the metal panel gets a lot stronger without needing to be thicker and heavier. This makes the corrugation a great way to efficiently use metal to support weight a lot greater than it would support if flat.
With the same sheet of paper, let’s fold it in half along the long side. This will make the paper virtually the same depth as the two sides of the fold. As mentioned above, the deeper the paper, sheet of steel, or beam, the less it will deflect.
The sheet of steel is virtually deeper because of the folds in it. These corrugated folds are what gives the steel walls strength for the same reason the folded paper is stronger than before it was folded.
Hold out the same piece of paper after folding it in half. You will see that it will not flop down like it did when it was just a flat piece of paper.
To take this a bit further, get a pair of scissors and cut out a chunk from the center of the folded piece of paper. This is very much like cutting the corrugated metal side walls of a shipping container for new doors and windows.
Doing this will make the paper flop down as it did when it was flat. That’s because there is not enough depth in the paper to hold its own weight up.
Things are only as strong as the strength of their parts.
Cutting the paper made a part of the folded paper too weak to support any gravity load on it. So, it bent down again.
This is why we must reinforce the cut openings of the corrugated metal sides when we cut into them for new openings.
The Advantages of Using Corrugated Metal When Building Shipping Containers
Durability
Along with the structural benefits of using corrugated steel when building shipping containers, the corrugation also make the containers durable.
For years, I have designed buildings with corrugated metal in the roofing and flooring systems for the same reason that the manufacturers of shipping containers use corrugated steel when building the containers.
The steel that manufacturers use when building shipping containers is called “Cor-Ten.”
Corrugated Cor-Ten steel is very durable and long lasting.
Cor-Ten is made to actually oxidize on purpose to create a protective coating all around it. This way, it can withstand the harsh sea sprays, broad temperature ranges, and the pounding of frozen elements like hail and snow.
Shipping containers are sometimes designed to last 25 to 30 years of shipping service. Some are slated to be used a maximum of 10 to 12 years before being taken out of shipping service. And many are used only once and a “one tripper” because it would be too expensive to ship back an empty container to pick up another cargo.
Not Susceptible to Damage from Insects
Unlike the use of timber construction materials that is susceptible to insect infestation, steel does not attract insects.
So, it will protect the contents, or occupants in the case of it being part of a shipping container home, from any threat of insects.
Protection from Rust
Because they are to be used on the open waters and in all types of inclement weather, shipping containers are made to be water-tight. The corrugated steel containers are carefully welded at joints to be water-tight.
Because they are water-tight, rust has a harder time forming and damaging the corrugated steel surfaces. There is a lot more things that can be shared about how shipping containers can be protected from rust damage.
I wrote another blog post that covers all of that at: https://liveinacontainer.com/do-container-homes-rust/
Fire-Proofing
Using corrugated steel also helps protect the contents of the shipping container from fire.
As discovered during fire tests to shipping containers by the U.S. Coast Guard, the corrugated steel is non-combustible and does not add to the fuel source of the burning cargo that would be placed within the shipping container.
Although, the steel will heat up and transfer the heat to other shipping containers stacked upon it.
Here is the report that was written by the U.S. Coast Guard in 1977: https://apps.dtic.mil/dtic/tr/fulltext/u2/a047513.pdf
Ease of Installation by Low Skilled Workers
Shipping containers are built in an assembly line fashion, much like automobiles are. So, the tasks of creating the corrugated metal and putting them together to create a shipping container can be assigned to several people who might be skilled only to do a sub-task.
There are workers trained to only transport the coils of metal to the cold forming crimper.
Other workers place the metal into the machines that crimp the metal to have the corrugation.
Still other workers will cut, weld, transport, paint, and do a lot of other sub-tasks that only require the workers to know how to do just their sub-task.
Shipping containers are manufactured every 24 hours and every day of the week. Because the manufacturing of the shipping containers can be systematized, the manufactures costs can be controlled and the production can be high.
Lightweight
Corrugated metal is does not weigh as much as other types of construction materials like concrete and masonry. Because it is relative lightweight, it is can be transported easily and economically
The Disadvantages of Using Corrugated Metal When Building Shipping Containers
Dents
One common problem with using corrugated metal on shipping containers is that they can dent easily. They are hoisted on top of each other and can bang into others when being stacked on a ship.
The more trips that a shipping container makes with cargo, the more chances that it will have dents.
If the shipping container gets dents, then it becomes more vulnerable to rust.
This is why it is often best to buy shipping containers that have not been used at all or has been used only once as a “one tripper.”
Appearance
Although the corrugation adds to the aesthetic charm while using them as a building element for homes, let’s face it, some people might think that they are too industrial looking to be used for homes.
If a person has this opinion of the corrugated metal appearance for shipping container homes, then they probably will clad the shipping container with another exterior finish which will add to the cost of the construction. Or, they won’t use shipping containers at all when designing their home.
No Thermal Insulation Qualities
The amount of heat that our homes restricts from passing through exterior surfaces like walls, roofs, and floors is very important these days.
Building codes are now requiring homes to have certain R-values. R-value is a measurement of the capacity of how a building product restrict heat to pass through it. The higher the R-value, the more restrictive the wall, roof, floor is at keeping heat from passing through it.
Corrugated steel does not restrict heat from flowing through it. It acts as a conductor of heat.
So, the home will need to have additional insulation near the corrugated metal walls and roof be code compliant and have the required R-Value.
Corrugated Metal is a Great Building Choice for Home Design
So, looking at the pros and cons of using corrugated metal in the construction of shipping containers, it is clear that it good outweighs the bad and is a great building material for home design.
