Connecting Shipping Containers: How to Join Shipping Containers Together

In the past few years, container conversions have popped up everywhere – from tiny homes to shopping centres, portable workshops, and even schools and hospitals. But for most people, a single container isn’t quite large enough.

Many container conversion projects start with joining two containers together. Connecting multiple containers gives you all the benefits of a conversion, with extra space for storage, work, or play. 

Before you go ahead and start welding containers together, here’s everything you need to know about connecting containers for more space. Find out how to plan your project, prepare shipping containers, and connect them securely. 

Why join shipping containers?

One of the most common conversions is joining two shipping containers together. But you can do more: connecting containers side-by-side, stacking them, or even joining them at right angles. It all depends on why you want to connect your containers. 

To create more space

Shipping containers are compact, portable, convenient, and come in a range of sizes. But you still might want some extra room. When you weld two containers together, the interior square footage doubles. That means more space for storage, office supplies, work tools, or anything else you can think of!

Some people also like to connect containers because it feels like having two separate “rooms”, instead of a single open space.

To create a unique structure

As well as increasing the space, joining shipping containers can create a unique structure. You can add height by stacking containers, or add width by placing them side-by-side. 

Because of this modular structure, you can also modify individual containers before you join them together. It’s often cheaper and simpler to upgrade the container before it’s installed as part of the main structure. 

For example, you could add height to a container workshop that was designed for tall farm vehicles, or add width to a container office to put in more desks. 

The benefits of joining shipping containers

Overall, converting a shipping container means that you can create a custom design. Connecting multiple containers gives you even more options to customise the space.

Container conversions are often cheaper than buying or building a traditional building. And if you ever decide to move, it’s easy to dismantle and transport containers to a new location. Once you get there, you can simply re-connect containers to form the same space. 

Joining shipping containers can even burnish your green credentials. When you convert a shipping container, you’re saving it from landfill—as well as reducing the usage of other building materials.

Need to dispose of your old shipping container but not sure where to start? Whether you’re looking for disposal options, recycling tips, or advice on repurposing, we’ve got you covered. Find all the answers you’re looking for in our guide How to Dispose of Your Old Shipping Container: Shipping Container Removal

Key considerations for joining shipping containers together

Shipping containers come in a wide range of sizes and conditions. Before you weld any containers together, you’ll need to pick the right type, as well as prepare the site where you want to place them.

Choose the right containers

You can buy new and used shipping containers in a range of standard sizes, from square 8 foot containers to extra-long 45 foot containers.

If you’re planning to join two containers, the most important requirement is that they should be the same size. They should be in good condition, with no damage or rust that could weaken the structure later on.

Prepare your containers

Whether your containers are new or used, start by cleaning them thoroughly. This prepares them for joining – and gives you the chance to check for structural damage.

Look over every inch of the containers for dents, rust, or other damage. Any problem areas will need to be repaired or replaced before joining two containers. Don’t forget to check the roof!

Carry out modifications off-site

It’s easier to make changes to individual containers before they’re connected. Remove walls or cut out doors and windows. You can also add beams or bracing columns if your design needs some extra strength. 

Ensure the ground is prepared and level

Shipping containers last longer when they’re placed on level, well-drained ground. It’s one of the easiest ways to protect your investment.

Start by levelling the ground where you want to place the containers. Remove all debris from the area. Depending on the ground, and your design, it’s often worth installing concrete blocks or wooden beams to act as shipping container foundations.

Next, place your containers one by one. Make sure that the first container is perfectly in place before you add another one. It will be much harder to make changes later on, so triple-check that everything is lined up correctly before you actually join the containers.

Secure your containers

At last, you’re ready to connect the containers together. There are several techniques you can use, from welding to bolting, caulking, and plating.

Add reinforcements

You might want to add extra reinforcements where the containers are connected. Support structures like steel beams or columns will help to distribute weight evenly across the containers and hold them in a stable position.

Seal and insulate

Sealing and insulation is essential for any shipping container structure. It regulates the temperature, prevents condensation from damaging the structure, and makes the space more comfortable to live or work in.

The most common ways to insulate a shipping container include:

• Caulk edges and corners to keep moisture and draughts out.
• Protect the roof with roofing cement, roofing materials, and a ridge cap. The roof is often the most vulnerable point on a shipping container, so it needs extra layers.
• Line the walls and roof insulation such as spray foam or panels.
• Paint the interior and exterior walls to protect the materials and make it look good.

How to join two shipping containers together

There are several different ways to join shipping containers together. However, whether you weld, bolt, or plate them, the process starts in the same way. The first step in connecting two shipping containers is to remove one long side from each container.

For shorter containers, you should leave 350mm at either end of the space to preserve its structural integrity. Then you can reinforce the opening with box section steel. If you’re working with a longer container, you’ll also need a supporting post that’s reinforced with box section steel, so that the opening doesn’t droop in the middle. This work is quite technical, so we recommend getting a container conversion expert to do it for you.

Next, you can line the containers up and join them with your preferred method. You can DIY this stage or leave it to the professionals, depending on the method you choose.

Welding

Welding shipping containers together creates a strong, durable connection. The most common processes for the job are Metal Inert Gas (MIG) welding, Tungsten Inert Gas (TIG) welding, and stick welding. 

Welding takes a lot of machinery, safety gear, and experience. It’s not recommended to weld containers together by yourself unless you really know what you’re doing. If you do plan to weld the containers yourself, make sure you wear safety gear and follow manufacturers’ instructions.

Plates and caulk

Another popular option is to connect the shipping containers with plates, and then fill the seams with caulk. 

You’ll definitely need a professional for this method. They’ll cut, frame, and reinforce the openings in the container walls. Then they’ll add threshold plates which cover the gap in the floor, ridge caps for the roof, and more plates for the walls and ceiling. Finally, caulking seals the gaps between the plates and the walls so that the structure is watertight.

Bolting

If you’re determined to DIY, then bolting is a safer and simpler option. This is when you secure two containers together with heavy-duty bolts and nuts. You’ll need to make sure the bolts are very tightly fastened.

The other advantage of bolting is that you can simply remove the bolts whenever you want to change the container layout or move the structure to a different place. 

As well as bolts, you can use a range of locks and twist locks to secure shipping containers. These are extremely effective if you just want to stack containers without connecting the internal space. 

Joining kits

Joining kits are another DIY option. The kit usually comes with PVC capping, tread plates, expanding foam, flashing, and paint to connect and finish your containers. 

Your joining kit should come with instructions and advice. Here’s a basic rundown of the steps to follow:

• Once the container walls have been professionally cut and framed, you can line up the containers.
• Fill any exposed gaps on the exterior with expanding foam.
• Add PVC capping where the two containers join at the top.
• Heat and lay the flash along the edges of the PVC capping and down the walls to make the join watertight.
• Paint of the flashband so that it blends in.
• Screw the floor tread plates across the join in the container floors.

Can I join more than two shipping containers together?

Shipping container conversions are booming. There are more inventions, innovations, and creations all the time – including bigger and more complicated structures.

In theory, you can join multiple containers together, using the methods above. But you’ll need to make sure that the structure is safe and strong enough to hold up its own weight. You should also check local regulations and whether you need planning permission for your shipping container structure to make sure that you’re in compliance. 

How to ensure the joined containers are safe

Joined shipping containers are very safe if they’re put together properly. That includes reinforcement at key points, such as the ceiling, floor, and opening areas. If your design is large or complex, then it might need even more support.

You can support the structure by preparing a stable, level foundation before the containers are placed. For larger structures, you should consider base plates that bolt the containers to the ground so there’s no risk of movement.

The bottom line

Joining shipping containers together is a simple, efficient way to increase the space of your container conversion. There are several different ways to connect containers together, ranging from professional systems to DIY kits. However, it’s important to make sure that your container conversion is stable, safe, and compliant with local regulations. 

FAQs

Can container conversions have plumbing and electrics installed?

You can modify containers to add plumbing and wiring. If you plan to join containers together, it’s usually easier to install plumbing and electrics before connecting the separate units.

Why is it important to choose the right container?

If your containers are different sizes, you may not be able to line them up for a secure connection. There’s also a risk that if one container is in poor condition, it could weaken the structure overall. Choose containers that are exactly the same size to join together and always check their condition.