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How to Join two Shipping Containers

Alexander is a professional engineer who specializes in the construction of affordable houses and structures using recycled materials.

Joining two Shipping Containers

For decades, the regulating body of such containers regulated the sizes and shapes of these containers to ease the burden of transport by freight or cargo. The purpose was to have them all with one standard size for accountability, as well as efficiency.

Every day, millions of cargo are transported over water and across borders, which allows economies to grow and develop. As we see them stacked over each other and placed side to side, then came the idea to merge the two into one wide space longer and wider than the container specifications.

If you'd like to join two or more shipping containers, or you're probably just curious about how engineers join these boxes, then you should read ahead and learn more.

Why Weld Two Shipping Containers

● To create wider and longer spaces in your shipping container home.

● It's still more cost-effective than building a brick and mortar house.

● It's a creative move.

● Encourages the nature of upcycling.

Merging Shipping Containers

Before we take a look at the entire process of joining these containers, let's have a look at some of the reasons why you would want to join them in the first place.

  • To create wider and longer spaces in your shipping container home.
  • It's still more cost-effective than building a brick and mortar house.
  • It's a creative move - seeing that the containers have that specific standard, you may feel limited in terms of creativity. Not anymore, you can still maintain the industrial space by doing so.
  • Encourages the nature of upcycling.

Well, there you have it. Those were just some of the reasons you should be encouraged to join two or more containers.

welding and joining two shipping containers together

welding and joining two shipping containers together

How to Join Shipping containers

So how exactly does this procedure of joining two shipping containers go? Let's find out.

These pre-fabricated containers can either be joined on-site or away from the site. Most engineers may encourage you to merge on-site to stabilize the shipping container home right from the foundation, especially if you want to stack it up. Besides that, here's the ultimate guide on how these containers are joined.

1. Prior Preparations

For almost everything you do, you have to have a plan on how you will join the two. This means the design of the structure. The design will allow you to know where exactly the second, third, or more containers will be added.

Some designs need the extra content to be just an added balcony. For a four-bedroom structure, you may need to stack up two extra containers with stairs to run up and down. So you need to view the architectural design and plan accordingly.

Planning also entails taking a closer look at the containers to be merged. Are they the same size or shape in dimension? You don't want to trim one horizontal side just to find the other one is slightly smaller.

You also need to check on the stability for stacking up. A concrete foundation will do a good job to ensure your shipping container home is sturdy on the ground. But what if the container has dents on the corners? Won't that cause structural damage?

The containers have to rack out properly so it all looks like one big structure. Once you have ascertained that all these things check out, move on to the next step.

2. Arranging Containers

The next step is to actually place the two structures together to see how they fit and begin the joining process. Here you can have either of two scenarios; a side by side structure or a stuck-up.

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Side by Side Structure

  1. Place the two units to be joined side by side, either left or right. Ensure the fit is great so it doesn't rack out when you are trying to make openings like doors and windows. Bring the two as close as possible, leveling the top rails and the corners.
  2. Add markings to where you joint two so you can cut the joining sides, horizontally, with the right fit.

Stacking up

  1. Using a crane, place the second container right on top of the bottom container ensuring they touch on every corner.
  2. Look to see if the stamina of the structure looks strong enough to hold the container or it's compromised.

For the side by side joining of shipping containers, after the markings have been made, you will use an industrial cutting tool to remove the wall from where you will be joining. To widen the space, it has to look like one big room without the strain marks.

After that use an expanded foam to fill gaps that may be visible after the cut. Add the PVC capping over the welded box section brackets protruding from the joined sides. Right at the upstands, screw in the capping in place using four screws to ensure it is firmly secured.

Each screw will be for each side pierced from the upper side of the PVC. Smooth the flash banding over the corner posts, down the sides of the join, and over the full PVC cap. The final stage is just to paint the flash and with similar paint.

For the interior space, place the tread-plate across the join, drill, and screw into place. One disclaimer, if your unit is ply lined and insulated on the inside, it's best to allow an extra half a day to properly finish boarding out the interior.


What's in The Joining Kit

For most customers, you will be aided with a joining kit to allow you to conduct a simple merge between the shipping containers. The joining kit will entail;

  • PVC capping
  • Trade plate
  • Flash banding
  • Expanding foam
  • Similarly colored paint

This kit should be adequate for you to conduct the joining by yourself at your own pace and convenience.

Step by Step Guideline on How to Join and Stack Shipping Containers

Shipping containers are just basic steel boxes made of corten steel made with specific sizes and shapes. They can easily be modified into shipping container homes but small in size, you may need to increase the interior space available.

In that case, you can choose to stack the second and third container to make a four or more bedroom mansion, or you can create a wide and spacious bungalow. In this case, you need to merge two or more containers to achieve your needs

Let's have an intrinsic look at how you can turn your 8 feet container into 16 feet or even 24 feet wide.

Joining Side by Side

The first step is to remove the full long sides of the containers. Depending on the length of the containers required, you can either retain 350 mm on each side of the aperture to provide strength to the container and reinforce the aperture with box section steel.

The purpose of retaining the space is to add some bit of sturdiness to the structure. Another method is by adding a supporting post, probably in the middle to enforce the strength of the box and to prevent the roof from sinking in.

After that, the containers are merged with four secure bolts as explained above to ensure no movement is detected. Similarly, you may also prefer quick and simple welding. Talk to your engineer about what is the best electrode to use to do this kind of task.

What About Stacking Them?

The second option involves stacking these shipping containers together, similarly to how they do in freight transport. Many people claim that stacking can be cost-effective as you will be saving on the land you would have otherwise had to pay for.

So with stacking, there are crucial elements to be considered before embarking in the actual joining of two containers. These include;

1. The Quality of Your Container.

Before you stack these containers together you have to ensure that they can, in fact, withstand the tensile strength of the upper container. The quality of your shipping container dictates how you can stack them as well as how many.

Your engineer can advise you accordingly on which type of cargo boxes you should buy for your shipping container home.

2. Corner-post to Corner-post

During transport, these containers are kept over each other with the corners touching from post to post. Their design and standard structure allow for easy stacking unless they are not of the same fit.

Conduct an inspection to have a deeper look at the corner posts where they retrieve the strength to hold the containers in place, as well as the flooring which adds a base layer. Here's a quick scenario of this;

If you are stacking 2x20’ containers and 1x40’ container, be sure that the 20s are on the bottom so all four corner-posts of the 40’ container have corner-posts to set on. If you do the reverse, the 20’ corner-posts will not have proper support and the 20’s could fall through the roof of the 40’.

It all lies in the math, if the two can't support the other efficiently, you can expect there to be damaging effects to the project including a fallen roof.

3. Securing Containers Together

Similar to the side by side joining of shipping containers, stacked boxes as well need to be securely placed together to avoid instability in the car of anything. These stacked boxes could be locked together using twist locks that close the containers together keeping the fixed.

4. The Practical Stacking

Now, here's where it all matters. The actual stacking begins here. After all the preparations have been made, you start the process of assembling your tools and equipment. In this case, you can choose between the forklift or a crane.

The best solution would be the crane because the forklift needs many more specifications. For example, forklifts can pick either the 20 or 40 feet container, but it needs to be able to spread that far apart.

This means the forklift pockets on 20’ containers are 69” from the inside of one pocket to the inside of the other pocket. If the forklift cannot manage that, then the fork extensions need to be at least 8 inches long so the forklift can pick the container up from underneath.

Also good to note, if the forks are not long enough, they will poke through the floor of the container. The forklift also has to be able to manage the weight of the shipping container. A 20-inch container weighs 5,000 pounds and 40 feet weigh just shy of 10,000 pounds.

Besides the forklift, other areas also have to be looked into including what to use to hold the stacked pieces together if they stack more than a specified number.

After the quick stacking, lock the containers together safely and move to other sections like painting or adding entrance and exits into the shipping container home.

5. After Process Factors

Once the work of joining is complete, you should check the area keenly to ensure there are no dents, holes, or spaces that can allow for water leakage. If you did a welding job, check to see the area gas a smooth finish that won't be visible.

Conduct the proper check so that everything checks out according to the plan. There shouldn't be stress lines or marks visible on the area that's been joined.

Shipping containers stacked on top of each other to make a hostel

Shipping containers stacked on top of each other to make a hostel

Final Thoughts on Joining Shipping Containers

You have learned that in fact, you can actually place two or more shopping containers in a side by side or over each other to build your beautiful shipping container home. As long as you're within the city limits, you can join as many as you want.

Stay keen to use the right containers with the right stamina to support each other. And if you're unsure, always make a point to consult with your engineers. They can aid you to hack the difficult areas like adding the piping as well as the flash banding.

Some Cheap House Plans Using Shipping Containers

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Alexander Okelo


Kevin Vitali from Tewksbury Massachusetts on April 13, 2020:

I am fascinated by some of the upscale shipping container homes. I wonder if they would pass building inspections here in New England.

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