Stacking shipping containers is an essential concept in many different shipping container use cases, ensuring efficient space usage whatever you’re using them for. Whether you’re stacking containers for shipping overseas, building accommodation, or you’re using containers on a construction site, it’s critical to know the best practices to ensure safe and secure stacking.
While stacking shipping containers is not a new concept, it is something that requires careful consideration. We’ll delve deep into shipping container stacking, uncovering why you might need to do it and the factors you need to consider before you start loading up your forklift.
Why stack shipping containers?
The main reason for stacking shipping containers is to maximise space efficiency. This could be in a variety of different locations where land is at a premium, from ports and docks to construction sites. The ability to stack containers offers greater flexibility for many different industries and requirements, from building modular buildings to ensuring efficient cargo storage and transport.
Here are some of the most common uses for shipping container stacking.
Port storage and logistics
With extremely high volumes of cargo, and limited land space, enhancing space utilisation by stacking shipping containers in ports is essential.
Container stacking in ports helps to reduce clutter while improving the management and organisation of different types of cargo. Similar types of cargo, destinations, or shipping dates can all be grouped for easier and quicker loading and unloading of ships. By stacking containers in this way, port efficiency increases, and turnaround times are reduced.
Modular buildings
In recent years, shipping containers have been increasingly used in construction, in a variety of ways. Thanks to their robustness, modularity, and ease of transport, shipping containers can be used on construction sites as temporary offices, or even as main builds themselves. We’re seeing more and more construction projects using shipping containers to build homes, permanent office spaces, and commercial spaces like cafes or pop-up shops.
Space-saving solutions
Many individuals and businesses are using shipping containers as space-saving solutions, especially since they are good for storage. As space savers, the ability to stack them on top of one another means shipping containers are the ideal solution for densely populated areas or land with a small footprint.
Containers can provide cost-effective and easily accessible solutions for temporary or permanent storage, additional workspace, or even more specialist facilities such as workshops.
Considerations for safely stacking your containers
Shipping containers are not lightweight pieces of kit, and careful consideration should be given when stacking them. There are several things you’ll need to think about, including weight distribution, height limitations, and environmental conditions.
You’ll also need to adhere to local and international safety regulations and guidelines. These are essential for preventing accidents and ensuring your containers are stacked securely, especially in busy residential areas or commercial environments.
Maximum height for stacking shipping containers
When stacking containers, height is a vital consideration. As layers of containers are added on top of each other, the centre of gravity rises, which increases the risk of tipping. Having an understanding of this is critical for safe stacking, particularly in areas with harsh environmental conditions such as high winds or seismic activity.
Different regions and applications will have specific legal limits and guidance on how high shipping containers can be stacked. Before you start stacking your containers, you’ll need to research and understand these regulations to maintain safety and avoid any legal complications.
In more general terms, shipping containers can be stacked up to five or six levels high. However, this will also depend on their condition and construction, and where they are being stacked, among other considerations. This standard stacking limit is based on the design strength of shipping containers and the common practices in shipping and storage industries.
There are usually much lower limits for stacking shipping containers in residential or commercial construction, typically a maximum of three levels. This is because several other factors need to be considered, including building codes, structural modifications, and occupancy requirements, as well as health and safety in more populated areas.
Maximum weight for stacking shipping containers
Just as it would be a consideration for transporting shipping containers, weight is a key factor to think about when stacking them. Shipping containers weigh quite a bit themselves, and that’s before you start filling them up or putting them on top of each other.
When stacking, you need to consider the weight of the empty containers, as well as anything you plan to keep inside them. This combined weight must be within the safe loading limits of the lower containers, so there’s quite a bit of maths involved. Additionally, you need to ensure the weight across the stack is evenly distributed.
The reason why weight limit adherence is so critical when stacking shipping containers is because overloading or unevenly loading containers can lead to structural failure, which can pose serious safety risks. This instability could also increase the risk of tipping or collapse, which can be extremely dangerous. When stacking shipping containers, you should ensure regular checks and balances are carried out to maintain a safe stack.
Weather and environmental factors
While ensuring you stack your shipping containers within the means of your control is important, you also need to stack them to withstand factors that you cannot control. When stacking, you need to ensure your containers are stacked to safely hold up against environmental impacts such as wind loads, seismic activity, and temperature variations.
To effectively prepare your container, you can use weather-resistant coatings or designs, alongside practising safe stacking techniques. You should ensure your shipping containers are securely fastened and anchored, which could include anything from additional strapping and bolting to embedding into foundations.
Inspecting containers
A final consideration for safe stacking is regularly inspecting your shipping containers for any signs of damage or wear and tear. This is especially important if they have recently been transported or exposed to adverse weather conditions. For example, if being transported overseas, your container may have faced harsh sea winds and saltwater that could cause rust if not appropriately looked after.
When inspecting your containers, you should pay close attention to the integrity of locking mechanisms, corner posts, and welds as these are common areas for structural stress to appear. You should ensure that any rust, corrosion, or structural deformities are rectified quickly to ensure safety can be maintained. We always recommend thoroughly inspecting your shipping containers before stacking, and at regular intervals once they are in place.
Stacking your shipping containers
Now that you’ve learned about the safety side of stacking shipping containers, we can move on to how best to stack them. We advise taking a systemic approach to shipping container stacking, ensuring thorough preparation has been undertaken so that safety can be maintained throughout the process. Here are the key steps involved in efficiently and safely stacking shipping containers.
Prepare your site
Before you begin stacking shipping containers, site preparation is the first step. Thoroughly preparing the site will ensure a safe and efficient stacking process, so it’s worth putting the work in here. Your site preparation will likely vary depending on your project and location.
On land
If you’re putting a stack of shipping containers on land, you’ll first need a stable and level foundation. To prepare this, you may need to lay a gravel base, construct a concrete pad, or undertake ground grading. Once your stable base is in place, it will be easier to facilitate the stacking process, considering factors such as access and traffic flow.
On a ship
Preparing to stack containers on a ship is a little different from land, with arguably a bit less manual labour involved. First, you need to ensure the ship’s deck is adequately prepared to handle the weight and distribution of the containers. This could involve checking the area’s structural integrity and repairing any areas of damage or weakness.
When you’re ready to start stacking, you should ensure there is space to arrange containers based on their destination and weight. This will help to maintain the ship’s balance and stability during transit.
Align your containers
With your stacking area thoroughly prepared, you can start to think about the alignment of your containers which is essential for structural stability. Your alignment needs to be accurate to avoid misalignment or uneven weight distribution as instability could lead to problems such as tipping or collapse.
Stackable shipping containers typically have four corner posts, specifically designed to bear the majority of the weight of the containers above them. To ensure your alignment is accurate, you can use alignment tools or machinery such as container handlers or forklifts equipped with alignment capabilities. This helps you achieve safe and precise positioning.
Decide your stacking method
Depending on what your intended use is, there could be a couple of different ways to stack your shipping containers. Usually, when stacking shipping containers for transport, smaller containers will be placed underneath the bigger containers. This might sound odd but there are a couple of logical reasons for this.
Firstly, smaller containers rely on the weight of larger containers to hold them down as this can improve overall structure and ensure they don’t move too much in transit. Secondly, having two smaller containers on the bottom and one larger container over the top of them means there are more corner posts to hold the weight of the bigger container, improving the overall structural integrity and weight distribution. Additionally, having two small containers on top of one large one can increase the risk of collapse.
Vertical stacking
The preferred method of stacking in most settings is vertical stacking, which is most suitable for uniform container sizes. This is where containers are stacked length to length and width to width, maintaining an efficient use of space. You’ll often see cargo ships with containers stacked in this way.
Vertical stacking requires meticulous alignment and secure fastening, which often involves twist locks or lashing rods to prevent any shifting or toppling of the containers.
Offset stacking
Another method, most frequently seen in modular building construction, is offset stacking. With this method, containers are stacked in a way that appeals aesthetically or has a functional necessity. For example, you may have one container stacked on top of another in an ‘L’ shape.
This method often requires additional planning and engineering, as well as potential reinforcement or support structures to ensure stability. Using the example above, you may need to install reinforcement posts to prevent toppling and provide structural integrity.
Secure your containers
No matter where your containers are stacked, securing them is key. However, this is especially important when containers are going to be in transit, and even more so when it comes to overseas travel. To prevent shifting or separation in transit, you should ensure your stacked shipping containers are secured with appropriate locking mechanisms.
Lashing rods
One method of securing a container in transit is to use lashing rods. These metal rods are designed to hold the bottom layers of the stacked containers to the vessel, offering greater stability to the stack. They are often used alongside twist locks and are particularly critical for high stacks or travelling through areas with adverse weather conditions.
Twist locks
To form unified structures on each stack of shipping containers, twist locks can be used to secure each container together and ensure greater stability. They work by fastening the twist lock into each of the four corner posts, before securing the container either to the ground or another container.
The bottom line
Stacking shipping containers isn’t as straight-cut as simply loading one on top of another. It requires careful planning and strict adherence to protocols, as well as a thorough understanding of limitations such as height and weight capacities. Whether you’re stacking shipping containers for storage, transit, or construction, you must consider safety as a priority.
Ensuring you carry out regular inspections, use equipment correctly, and prioritise maintenance and safety are all key elements for successful stacking. By following our guidance, you’ll be able to achieve optimal space utilisation and operational efficiency safely and securely.
FAQs
How much wind can a container withstand?
Shipping containers are robust and have been designed to ensure strong winds and adverse weather conditions. When properly anchored and secured, there should be no problem with high winds. However, wind tolerance also varies depending on the container’s configuration and anchoring so it’s important to check the condition of your container before transporting.
Do you need a crane to move a shipping container?
A crane is not essential for moving a shipping container but they are particularly useful for lifting containers in high-volume yards. The downside to cranes is that they can be expensive and often require reinforced surfaces.
For smaller spaces or fewer containers, forklifts and truck cranes are often more flexible and cost-effective options. Reach stackers can also be an efficient option when you need to quickly stack a few containers, and they can be used on various terrains.
Looking for more advice on how to stack shipping containers or in need of professional services? Contact us today for a free consultation. No obligations, just help when you need it.
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