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Shipping Container Foundations: Getting the Base Right for Your Shipping Container

22 May 2024

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shipping container foundation

Shipping containers have many different uses. In recent times, they have become almost permanent solutions for traditionally constructed buildings such as homes, business premises, and other living spaces, as well as storage. 

However, it’s not enough to simply place your shipping container on the ground you intend to use. A stable and durable foundation is essential for ensuring your container remains secure with structural integrity. 

What is a shipping container foundation?

A shipping container foundation refers to the base on which your shipping container is placed. In general terms, the foundation is largely the same as any other foundation you would construct when placing a large structure or building on top. 

Ground foundations act as anchor points for your structure, helping to distribute the shipping container weight evenly across the surface underneath, such as soil, concrete, gravel, or another substrate. Foundations are necessary for shipping containers since they can be placed almost anywhere. This means the ground underneath could be uneven, unstable, or even difficult to predict.

How to know if you need a foundation for your shipping container?

Knowing whether you need a foundation for your shipping container will depend on several factors. Firstly, you’ll need to consider where you plan to keep your container and how you’re going to use it. For example, if you’re using your container as simple storage on a private piece of land, you may not need to dig new foundations. 

If you’re planning to use your shipping container as a living or working space, you’ll likely need a more robust foundation to ensure long-term support and safety. For living spaces, you may also be subject to more stringent planning conditions which could require a new or more solid foundation to be built, especially in areas prone to unstable environmental conditions. 

You’ll also need to think about your specific project requirements, the site conditions, and any regulatory considerations relevant to your structure. Before you can decide whether you’ll need a foundation for your container, you should evaluate the site thoroughly, looking at the soil type, drainage conditions, and terrain slope. Each of these factors will help you understand the stability of the ground and whether it is settled or shifting, which will inevitably impact the stability of your container. 

Why is it important to have a foundation for a shipping container?

No matter what you’re using your shipping container for, it’s vital that you properly secure and support it. Having a solid foundation underneath can help secure your container long-term, ensuring it is protected from ground moisture. In doing so, you’ll reduce the risk of structural damage, while minimising wear and tear over time. This is especially important for people using containers as habitable spaces.

Prevents the container from sinking

Even when empty, shipping containers are heavy, but having a solid foundation can prevent them from sinking deeper into the earth. When fully loaded with cargo or furniture when used as a residential space, shipping containers become even heavier, increasing the chance of them sinking into the earth without a proper foundation. 

With a foundation in place, the weight of your container will be more evenly distributed across the surface underneath, which prevents concentrated pressure points that could lead to sinking or damage.

Keeps the container level

Solid foundations provide stability and support for your shipping container, which can help to keep them level. This is crucial if you’re using your container as a living or workspace. Without a foundation, you leave your container at risk of settling, shifting, or even tipping over if the ground beneath is particularly volatile. In turn, this would compromise the structural integrity and safety of the structure, putting you, your belongings, and potentially others at risk.

Levelling your shipping container is also important for the structure of the container itself. Without being housed on level and solid ground, the container’s structural elements could shift and warp over time, leading to damage and problems using the container. For example, with structural warping, any installed windows or doors may not open and close properly.

Minimises container corrosion

Shipping containers are made of steel and over time can be susceptible to corrosion. This becomes a greater risk if your container isn’t supported by a solid foundation, especially on the underside. With a foundation, contact with moisture or groundwater is minimised, which is a leading cause of rust, corrosion, and rot. 

The problem with corrosion is that it can affect the durability of your shipping container, increasing the risk of container walls becoming damaged or letting in leaks. This can require extensive renovations to fix, which can be both costly and time-consuming.

How shipping container foundations work

In simple terms, shipping container foundations work the same as any other foundation and are designed to hold the shipping container up straight and securely. With a stable platform for the shipping container to be placed onto, it remains level and secure, minimising the risk of structural damage, shifting, or tilting over time.

To design a robust foundation for your shipping container, it’s important that you understand the key elements of how they work. Before you start thinking about your shipping container foundation, you should consider the foundation-bearing capacity, foundation settlement, and soil expansion.

Foundation-bearing capacity is vital for minimising settlement or failure, relying on soil type, density, and moisture content. You must ensure the foundation’s capacity exceeds the container’s weight (when filled) to prevent settlement and maintain stability. Understanding the soil type on your intended site helps you to plan by enabling you to determine bearing capacity without on-site measurements.

Foundation settlement and soil expansion considerations are essential for supporting container function. When foundations are compressed under the weight of the container, settlement can happen. Soil expansion happens when there is increased moisture content, which is particularly troublesome in clay soils. To combat these issues, proper drainage and moisture control are vital.

Types of foundations for shipping containers

There are several types of foundations you can use when placing a shipping container. Each type has its benefits and drawbacks, which can make it easier for you to decide which type of foundation best suits your needs. The three main types of foundations for shipping containers are temporary, semi-permanent, and permanent. 

Temporary shipping container foundations

If you’re only planning to use your shipping container in one location for a short time, you might consider a temporary foundation. This type of foundation will ensure your container is level and off the soil to prevent corrosion, but it can still move freely. There are a few types of temporary foundations you can opt for, depending on your needs and the ground type. 

A benefit of temporary foundations is that they are quick to install, with most people able to create a temporary solution shortly before the container arrives. They are also easy and cost-effective to implement. For example, you could use blocking, which is where a shipping container is propped on concrete blocks. 

While temporary foundations are often considered the cheapest and easiest method, they are also the most risky. With temporary bases, the container is still able to move freely. If your support is not sturdy enough, you could risk your container shifting or even toppling over.

Wood beam foundation

wood beam foundation for shipping container

Wood beam foundations are an easy and affordable option for temporary container foundations. In this method, the shipping container is placed on top of wooden beams, creating a void underneath. Wood beam foundations work particularly well when containers are placed side by side, such as in a storage facility. However, if you’re looking for a temporary solution that also looks good, this option may not be the most aesthetically pleasing.

Gravel foundation

Some people opt to use a gravel foundation, which is where gravel is spread out over an area and compacted to create a supportive base. This method is best suited for containers that won’t have people going in and out of them, such as for storage space. While it seems similar to just placing a container on the ground, with proper container anchoring, this method can be sturdy when used over a longer period. 

gravel foundation

The best gravel for this type of foundation is crushed stone with jagged edges that interlock together to create more strength. Stones should ideally be smaller than ½ inch so they can be well compacted. Gravel bases provide some stability and drainage, but they can make your container more susceptible to shifting and settlement over time. 

Concrete block foundation

Concrete blocks can be placed directly onto soil to create a temporary foundation. Blocks are stacked to create a raised bed that lifts the container off the ground, leaving room for ventilation and drainage underneath. For optimal weight support and greater stability, concrete blocks should be arranged in a grid pattern and placed upon a level and compacted surface, such as gravel or compacted soil. 

concrete block foundation for shipping container

Concrete blocks are known for their durability and strength and can be tailored to suit different container sizes, weights, and configurations. However, there could also be the risk of uneven weight distribution and settling issues with this method, if the blocks are not properly levelled or supported.

Semi-permanent shipping containers foundations

Semi-permanent container foundations can help secure your container with the benefits of a permanent base while offering the ability to remove them. They can be a great solution for shipping containers that only need to be temporarily placed before they move to a more permanent location. However, they do come with some drawbacks as well – they can often be complex to install, as well as costly. 

When deciding what type of semi-permanent foundation to use, you should consider factors including duration of installation, budget, site conditions, and mobility requirements. You’ll need to choose a method that offers the right level of support, while still meeting your needs. 

Helical pier foundation

This type of container foundation is often referred to by many other names, including soil screw, screw pile, helical pile, helical per, screw anchor, and helical anchor. It involves twisting a large metal screw into the soil with hydraulic machinery which immediately supports loading. This makes them ideal for containers that need to be supported right away. 

However, helical pier foundations are particularly vulnerable to corrosion. This is because they’re commonly made of steel, which when exposed to moisture and soil in the ground, can cause corrosion. In turn, this corrosion can weaken the integrity of the piers, compromising the stability of the foundation.

Specialty pin pile foundation

Pin pile foundations are a type of micro-pile, which means the pile itself has a narrower diameter than common piles. Once the piles have been installed into the ground, you can place the structural member you need to support the shipping container on top of the pile caps. Some manufacturers now make a system of pin piles and caps that work together, creating an integrated foundation solution. 

The key drawback of this solution is that it requires specialised equipment and expertise which can be expensive and time-consuming compared to other methods. 

Permanent shipping container foundations

If your shipping container is going to be in one place for a long time, permanent foundations are the ideal solution. Once built, these foundations cannot be moved without demolition or heavy equipment, which makes them ideal for living spaces. 

Permanent foundations are the best solution for keeping shipping containers level, secure, and away from groundwater permanently. However, depending on the method you choose, they can be complex, time-consuming, and expensive to build.

Concrete slab foundation

A concrete slab foundation is commonly used for traditionally constructed houses due to its support, durability, and smooth finish, which makes this type of foundation a great choice for shipping containers being used as living spaces. Concrete slabs are ideal for soft soils and warm climates. 

Using a concrete slab foundation means you don’t have any hollow spaces underneath the container, ensuring it’s sealed and secure from insects or vermin. However, to install, you will need to do a lot of digging to make sure the perimeter of the slab is below frost depth. In this case, you could be better off building a concrete basement instead. 

Concrete strip foundation

Also known as a trench foundation or continuous footing foundation, a concrete strip foundation combines pile and concrete slab foundations. It’s often a cheaper alternative to a slab foundation and can be great when working with softer soil. Plus, it has a much larger ground contact area because it contacts the ground along a line rather than a point.

The strip can be placed around the perimeter of the counters or at the top and bottom of the container, making it a versatile option. Some people use two strip foundations, supporting the container at each of its two short ends. The potential drawback of a concrete strip foundation is that cracking can occur due to soil movement or settling. In areas with poorly compacted soils, cracks can appear over time, compromising structural integrity which could lead to water leaks or building instability.

Concrete footing

Concrete footing foundations spread isolated point loads over a larger area, creating a more stable base for your shipping container. They’re often referred to as isolated spread footings or bell footings. 

concrete footing foundation

To install, you would need to dig a traditional straight hole with a regular auger, before lowering a special bell auger into the hole to scrape out additional soil and expand the footprint at the bottom. Concrete is then poured. If time isn’t on your side, you could use precast footing and piers so you don’t need to mix concrete yourself. 

The key drawback with this type of foundation is that it can be vulnerable to frost heave in cold weather. When water in the soil freezes and expands, it can place pressure on the concrete footing. This can lead to cracks or lifting, compromising the structure’s stability.  

Pile foundation

Sometimes known as friction or driven piles, pile foundations are good for locations where the soil near ground level has a low bearing capacity or is too soft to support concrete slabs. To create this foundation, you need to hammer cylindrical solid steel tubes through the soft soil until you reach a hard surface capable of supporting the weight of your container. Sometimes, piles can get a portion of their strength from end bearing if a lower soil stratum with greater bearing capacity is reached. 

Pile foundations are typically the most expensive type of permanent foundation, but they can also be vulnerable to unforeseen subsurface conditions during installation. Conditions such as rock, layers of soil, or groundwater can complicate the build and increase costs. On some occasions, piles can meet obstructions underground which could mean they need to be relocated.

Pier foundation

If you’re looking for a permanent foundation for your shipping container that is easy to install and affordable, pier foundations are worth considering. Similar to pile foundations in appearance, pier foundations consist of concrete cubes with reinforced steel bars to add strength. The difference with pile foundations lies in the shape, function, and installation.

pier foundation for shipping container

Pier foundations bore through soil with lower bearing capacity until strata with better material for supporting a heavier load are found. This type of foundation has become popular for shipping container homes and other permanent structures. However, it can be susceptible to soil erosion or scouring, particularly in areas with high water flow or tidal action. Pier foundations also require more maintenance and inspection to ensure long-term integrity and structural stability.

How to choose a foundation for your shipping container?

Choosing the right foundation for your shipping container will depend on how long you plan to house your container in your desired location. If you’re only keeping your container in one place while you source a more permanent location, a temporary foundation would be sufficient. However, if you know you’ll be keeping your shipping container in the same place, it’s always best to choose a permanent foundation that offers more stability and security long term.

While your choice largely depends on the length of time your container will be in one location, you’ll also need to consider factors such as the soil type in the area, the local climate, your budget, and how much time you have to prepare the ground.

Foundations for multi-unit container structures

Often, shipping containers are used as part of a multi-unit structure. This can require slightly different thinking when it comes to creating a solid foundation, but several options will provide the right support and stability. The best foundation types for multi-unit container structures include:

  • Concrete slab foundations – these are often reinforced with steel rebar to support the weight of multiple containers stacked atop one another.
  • Concrete footings – with individual pads or piers poured at specific points, this type of foundation offers flexibility in container positioning and can be more cost-effective.
  • Piers and pillars – strategically placed to support the corners or midpoints of the container, this type of foundation allows for underneath airflow to help mitigate moisture buildup.
  • Steel beams – often used to support the containers along their length, steel beams provide robust structural support that can accommodate various configurations.
  • Helical pile foundations – with multi-units being particularly heavy, helical pile foundations can offer optimal support for very heavy loads.
  • Hybrid foundation systems – combine several types of foundations, offering a more tailored approach that meets your support requirements.

Important considerations for shipping container foundations

When you first start thinking about your container foundation, there are a few things you’ll need to consider to ensure your base is durable and your shipping container is secure and stable. By understanding these considerations from the outset, you can make sure your foundation is installed optimally for the site conditions while being able to provide stable support for your container.

Understand your foundation loads

The key consideration in design and planning is the load weight your foundation can hold. You’ll need to think about the weight of your container and its contents to assess how much it will push down on the ground. 

  • Dead loads – known as permanent loads, dead loads include the weight of materials used in construction and all fixed equipment. This will include floors, walls, roofs, solar panels, plumbing, electrical equipment, and HVAC equipment. Essentially, anything that isn’t generally moveable should count as a dead load.
  • Live loads – anything that’s not permanently fixed to the building but will be in it at some point would be a live load weight. This could include anything from people to possessions. You’ll also need to consider live loads if you’re having work done on the container. For example, on a roof, a live load must include the weight of maintenance workers.
  • Flood loads – floating, lateral movement, or collapse due to flood water will be a flood load. To understand flood loads, you need to analyse the flood zones of your property and your structure design.
  • Wind loads – any pressure imparted due to wind, often laterally against the container, will be your wind load. These can vary depending on your location, as well as the type of land near your structure. For example, this can change based on trees, hills, and buildings in the area.
  • Snow loads – this is the weight imposed by snow on the roof of your container. 
  • Seismic loads – if you’re in an area that has experienced earthquakes and other seismic activity, you must include and analyse these events as part of your foundation design.

While some of these seem a little extreme or inapplicable to your location, these equations can give engineers a way to aggregate the various loads into one number. This will help to determine the overall load that your structure will impart on your foundation, even though they are highly unlikely to all happen at one time.

Account for frost heave

Nearly every type of soil has some moisture or water in it, so you must consider frost heave when designing your shipping container foundation. The frost line is a soil depth specific to your location, above which is a chance of the ground freezing and causing frost heave. 

Know how to attach your shipping container to the foundation

While we talk about ‘placing’ your shipping container on top of its foundation, it’s not enough to simply dump it down and leave it there. Your shipping container needs to be attached to the foundation to offer greater stability and security, especially if you’re using it as a living space or you’re creating a multi-unit structure. 

The most popular method of attaching containers to foundations is by welding the bottom of the container to a large steel plate. Another method is to use twist locks. However, these can only mate with the container corner fittings, so if additional points of contact between the container and the foundation are needed, twist locks cannot be used.

Choose the right place for your shipping containers

Evaluating your container site is vital when planning your foundations, regardless of what you’re using it for. Firstly, you’ll need to ensure the space you’ve selected will fit your container. Next, you need to think about the location accessibility for container installation, maintenance, and use. 

It’s also a good idea to consider how easy it is to access utilities such as plumbing, electrical wiring, and ventilation if you’re going to be using your container as a living or working space. By thoroughly assessing the site for your container, you can ensure you have the right space for your requirements and the foundations you need.

Costs involved with the foundation

A final key consideration for container foundations is budget. Like anything, different foundation types incur different cost levels, so it’s important that you consider all options concerning your budget before you make a decision. In addition, your site location will play a role. You need to think about the condition of the site and what will be required to ensure your foundation type is achievable and stable.

For example, sites with poor soil quality or uneven ground could require more preparation, which will inevitably increase your costs. Likewise, your foundation materials will impact your budget. High-quality concrete, reinforced steel, and helical piles will likely be more expensive than some other options. 

Another cost to consider is equipment and machinery at installation. Depending on the type of foundation you use, as well as site condition, you may need specialist equipment to thoroughly prepare the ground and foundations so your container can be safely installed.

The bottom line

No matter what you’re planning to use your shipping container for, having a solid foundation in place is crucial. Whether you choose a temporary base or a permanent foundation, be sure to consider all your requirements before you make that final decision. 

If you need advice on choosing the right shipping container for your needs, or you’re keen to get more information about creating a secure foundation for your container, reach out to us today.

FAQs

What is the best base for a container?

The best base for your shipping container will really depend on your requirements. There is no one-size-fits-all all. However, if you’re planning to keep your container in one place for a long time and want to avoid building a slab, concrete footings could be an efficient and cost-effective choice.

What footings are required for a shipping container?

The footings required for your shipping container will vary depending on your project and intended use. However, pier footings are a popular choice due to their strength and stability.

How thick does a concrete slab need to be for a shipping container?

The thickness of the concrete slabs under your shipping container should be enough to support the weight of your container. Generally, for single containers, concrete slabs should be at least four inches deep to ensure optimal stability.

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