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Guidelines for Stacking Shipping Containers

How many shipping containers can you stack?
How are your skills when it comes to stacking shipping containers? If you’re an employer, are your dock or shipyard workers experts at stacking shipping containers? If the answer to either of these question is no, here are some ways to avoid stacking accidents, worker injuries and expensive OSHA fines.

Shipping and cargo containers make it possible for products to be transported throughout the world in a safe and cost-effective manner. They’re easy to lift, unload and store and can be used to hold virtually any type of product that needs to be shipped. Regardless of what they contain, the key to workplace safety and preventing employee injuries is proper stacking.  If your business involves stacking cargo containers, it’s important that you and your workers understand how it’s done the right way.

Although OSHA has established clear guidelines for shipping container safety, many companies aren’t sure of the proper way to stack containers. (FLC), a recognized leader in online forklift certification training since 2002, offers 100% OSHA-approved forklift safety courses, which can affordably teach your workers how to correctly stack shipping containers.

Here’s some of what your workers need to know about stacking containers that they’ll learn through our training:

How to safely stack shipping containers

✓ Shipping container height stacking limitations

✓ The maximum number of shipping containers in a stack

✓ Inspecting shipping containers before stacking

✓ Best container stacking methods

✓ And much more

To create a safer and OSHA compliant workplace for your employees, enroll them in one of our forklift training programs today.


Once they’ve been offloaded from the ship, the worker is faced with decisions such as how many containers can be stacked atop each other, what is the maximum shipping container stacking height and what are the proper container stacking methods on dry land?

Correct stacking techniques revolve around two key factors, which are stack height and stack stability. Here are the basics:

✓ Container stack height regulations.

On land, there are no height restrictions on stacking shipping containers, although reasonable caution should always be exercised. Your company’s safety supervisor should establish on-site stacking procedures, which will vary depending upon whether the containers will be stacked in warehouses, on open land or The maximum safe shipping container stacking height should take into account the type of lift equipment that’s used and where the containers will be stacked.

✓ Container stack stability.

Stacking containers for an open sea voyage is more difficult than stacking them on stable Whether they’re stacked on board a ship or on land, the heights of the stacks present different safety hazards. For example, the containers’ bulk and weight create an even higher level of risk when bouncing around on the deck of a cargo vessel.

Regardless of the storage location, workers should always check with safety personnel or their supervisors before stacking shipping containers.


Here are some recommended procedures for safely stacking shipping containers on land:

✓ Inspect the containers.

Shipping containers should always be inspected for visible signs of cracks or dents before stacking. Check the sides, sub-flooring and corners posts for signs of damage or wear. Repair or replace any units that show signs of structural damage. Containers should also be checked inside and out for the presence of rust. On long ocean voyages, weak containers can result in damage to their contents and put the ship’s crew at risk of injury or death. Immediately repair or replace any units that show signs of structural damage.

✓ Use corner posts when stacking.

Think of shipping containers as stackable giant Legos. For maximum stability, containers should be stacked corner post to corner post. A container’s four corner posts should align directly with the corner posts of the containers immediately above and below. When stacking containers of different sizes, such as stacking one 40’ container and two 20’ containers, the larger 40’ container should be placed on top, since placing the two smaller containers on top will increase the risk of the stack collapsing.

✓ Use lashing rods to prevent sliding.

Whether they’re on a truck or ship, containers should be secured with lashing rods to keep them from sliding while in transit. Adding twist-locks to the containers will increase stability, and will also reduce the chances of an accident.

✓ Have only properly trained and certified forklift operators do the stacking.

Because there’s a certain degree of risk involved, handling a forklift requires skills acquired through training and experience. Forklifts are bulky and slow-moving pieces of equipment, but even at low speeds an impact can cause serious damage to people, products, and equipment, including tip over accidents that can result in fatalities. Using untrained. and uncertified forklift workers is not only against the law, it can cost your business a lot of money if OSHA cites you for a violation. To protect your employees and your company, enroll your operators in FLC training today!


Techniques for stacking shipping containers on the deck of a ship are different than stacking them on land. Here are a few of the differences:

✓ Choose the appropriate type of on-board stowage.

The two types of storage on a container ship are “fore and aft” and “athwartships.” Fore and aft stowage onboard the ship is lengthwise, while athwartships refers to horizontal stowage at right angles to the ship’s center. The correct type of stowage depends on the size of the ship and weather Fore and aft storage offers better protection against high winds, crashing waves, and rough seas.

✓ Stack using corner posts.

When stacking like-sized containers on top of each other, align them corner post to corner post, since the posts and flooring are designed to bear the weight of both the container itself and those above it. Corner posts should extend slightly lower than the bottom of the container and a bit higher than its top. When stacking different size containers, the smaller containers should always be on the bottom. By doing this, all four corner posts of the larger top container rest on corner posts of the containers immediately beneath them.

✓ Secure the containers to prevent slipping and toppling.

Traveling on the sea is much rougher than traveling across land, which makes it even more important that the containers are secured against slipping and sliding. Cell guides with vertical guide rails should be used to keep the containers in place. This also helps ease the pressure from the top containers on those at the bottom of the stack. Lashing rods and twist-locks are used to secure the container stacks to the vessel’s deck, which also helps prevent slippage.

✓ Choose the right lift equipment. 

Forklifts are frequently used to stack containers on ships, although their use depends on the type of forklift and the height of the stack. Container forklifts are designed to handle both 20’ and 40’ containers. Some types of forklifts may not be able to handle the job, in which case cranes might be needed. The capabilities of a particular type of forklift should be confirmed before it’s used to stack containers.

✓ Container Stacking Safety.

There are several factors that determine the safest methods for stacking shipping containers, the most important of which is using only forklift operators who have been properly trained and certified and understand how to minimize the risk of workplace accidents. has the forklift training your business needs to comply with OSHA guidelines. Regardless of where, when or how you use forklifts, FLC covers all the key elements of forklift safety practices in the workplace, all in an easy-to-understand format. Contact us online or call at (888) 278-8896 today to enroll your operators and you’ll soon have a safer and more productive workplace!

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