You will always need a foundation for your shipping container home. This is because the ground moves a considerable amount. The ground can rise, sink or slide. This movement can be sporadic and is usually very slow. Even though it is often barely noticeable, this slight movement can affect how level your home is. A foundation provides a solid, stable platform for your building. Without this solid platform, the ground’s natural movement can cause the containers to split and separate. The ground underneath your building can also be comprised of different materials. For example, part of the ground could be hard rock and the other part soft clay. This creates an unevenness which can allow your home to shift since the load isn’t equally distributed. One result could be having doors that are incredibly difficult to open and close. A solid, well built, foundation will ensure the weight is appropriately distributed. It will also help prevent moisture and the corrosion that occurs as a result of this moisture.
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​Types of Shipping Container Home foundations:
The four main foundation types which can be used with container homes are pier, pile, slab and strip.  There are other types of foundations but these are the most commonly used with container homes.
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Pier Foundation:
Pier foundations are the most popular choice for shipping container homes for numerous reasons. They are relatively inexpensive, and quick to construct, a pier foundation is comprised of concrete blocks. Each concrete block, or pier, is generally 50 cm X 50 cm X 50 cm and containers reinforcing steel inside to improve the concretes strength in tension.
With shipping container homes, the concrete piers are generally laid at each corner of the container. And, with the with larger 40-foot containers, an additional two piers can be placed midway down each side of the container.
You save a lot of time and money with pier foundations because you don’t need to excavate a lot of earth at all. You only need to excavate the ground for the piers, which are generally 50 cm X 50 cm X 50 cm. Compare this to a slab foundation where you will need to excavate basically the entire area under the container. Another great reason to use a pier foundation is that other foundations, such as pile foundations, require expensive specialized equipment.
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Pile Foundations:
Pile foundations are used when the soil type is too weak to support a concrete base. This type is the most expensive type of foundation covered here. Piles (cylindrical solid steel tubes) are hammered into the ground through the soft soil until the piles reach more suitable load-bearing ground. Once the piles are secured in place, they are traditionally capped with a block of concrete. So, once you have secured all your piles you end up with a grid system of concrete caps which above ground look visually similar to concrete piers.
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Slab Foundation:
A slab foundation is a popular choice when the ground is soft and requires an equal weight distribution. However, it is more time-consuming and more expensive to build than a pier foundation. If you are going to use a slab foundation, be prepared to dig a lot!. a slab foundation is a concrete slab onto which your containers are placed. The slab foundation is generally slightly larger than the footprint of your home.
If you are building with two 40-foot shipping containers, your slab foundation would typically be 18 feet wide by 42 feet long. This would provide an overhanging foot of foundation around the perimeter of your shipping containers.
A huge benefit of slab foundations is that because it provides a solid base, there is no hollow space in the foundation. This prevents future problems such as termite infestations.Unfortunately though, because of the additional concrete used and the vast amount of space which needs to be excavated, slab foundations are significantly more expensive than pier foundations.We often see slab foundations used in warmer climates where freezing isn’t a concern. However, they do increase the potential for heat loss when ground temperatures drop below the interior temperature because the container can conduct heat into the ground, which transfer more heat than via convection into the air.
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​Strip Foundation:
A strip foundation (also known as a trench foundation) is somewhat of a combination of the previously mentioned pier and slab foundation. The strip foundation, shown below, is simply a strip of concrete which is laid to support the containers. The concrete strip is normally 1-2 feet wide and 4 feet deep. The strip can either go around the perimeter of the containers or it can be laid at the top and bottom of the containers instead. It is ideal to use when you’re looking for a cheaper alternative to the slab foundation but have slightly less firm ground to lay the foundation on. For locations where the ground stays damp much of the time because of large amounts of rain, a rubble strip foundation using loose stone below the concrete strip can be used. This stone allows the water to run through and drain away. Like all the foundation types mentioned, strip foundations also have their weaknesses. For instance, strip foundations have low resistance to earthquakes. Also, due to their shallow form, strip foundations are best suited for small and medium-sized builds.