Complete Buying Guide: How to Choose a Container Support – Any Ground Type

Why a container support is essential on unprepared ground

Placing a shipping container directly on the ground, without preparation, exposes the structure to several risks: sinking into soft terrain, deformation of the bottom rails, difficulty operating the doors, or even tipping if the ground is sloped. The container support is a simple accessory that solves these problems by slightly raising the container and distributing loads over controlled support points.

A shipping container rests on four corner fittings standardized according to ISO 668 and ISO 1496. These corner fittings are designed to transmit lifting and stacking forces. When a container is placed on the ground, these four points carry most of the load, even if the bottom rails help distribute it. Placing supports under the corner fittings or under the rails, near the corners, distributes the forces and avoids putting weight on a less reinforced central area. This also limits the risk of deformation of the floor or bottom cross members.

This guide helps you choose a container support usable on any ground type: bare earth, gravel, compacted sand, concrete, asphalt or pavers. It details the technical criteria to check, load capacities, available materials and best installation practices.

The essential technical criteria for choosing your support

Dimensions and bearing surface

The support must provide a sufficient bearing surface to receive the corner fittings or rails of a standard container. A format of 40 cm long, 26 cm wide and 45 cm high is common and suitable for 20 and 40 foot containers. This size stabilizes the container while remaining manageable by hand.

The height of 45 cm is a good compromise: it raises the container enough to limit contact with ground moisture, without making door access too difficult. It also allows a pallet truck or forklift to slide under some models, depending on the configuration.

Weight and handling

A 6 kg polypropylene support can be moved by one person without lifting equipment. This is a considerable advantage during installation, as the position of the supports often needs to be adjusted several times before finding the right balance. Conversely, a concrete or solid wood support can weigh several dozen kilos and require two people or a machine.

Maximum load and working load

Two values must be distinguished: the maximum load on hard ground and the working load. The maximum load corresponds to the ultimate limit that the support can withstand without breaking, under ideal conditions (flat and rigid ground). The working load, more conservative, includes a safety factor and corresponds to normal use.

For this model, the maximum load on hard ground is 5.5 tonnes, and the working load is 2.1 tonnes for a pressure of 2 daN/cm², whether on a single support or between two supports. The safety factor used is 1.5, in line with common practice for this type of support accessory. These values assume correct installation, on a flat and sufficiently load-bearing surface, and a balanced distribution of the load.

It is essential to check that the actual container load (empty weight + cargo) divided by the number of supports does not exceed the working load. An empty 20-foot container weighs about 2.2 tonnes, a 40-foot about 3.8 tonnes; once loaded, the weight can reach several dozen tonnes. The load is distributed over the four corners, meaning each support may have to bear a significant fraction of the total weight.

Material: polypropylene, wood, concrete or steel?

Recycled and recyclable polypropylene offers a good compromise: lightweight, resistant to moisture, impacts and common cleaning products. Unlike wood, it does not rot, crack or feed insects or rodents. Unlike steel, it does not rust and is unlikely to scratch or mark surfaces. It is also lighter than concrete or solid wood.

Wooden supports are easy to find and inexpensive, but they rot on contact with moisture, attract insects and lose their mechanical properties over time. Concrete supports are very resistant to compression, but heavy, difficult to move and brittle on impact. Steel plates are strong but rust, slide on some grounds and can mark surfaces.

Polypropylene withstands an allowable pressure of 35 daN/cm² at 20 °C, which corresponds to a high load capacity for a small volume. It withstands pressure washer cleaning up to 80 °C and 200 bar, which removes mud, soil residue or hydrocarbon splashes without degrading the material.

Stacking and modularity

The ability to stack up to five supports is an asset for compensating for a slope or localized subsidence. This modularity allows fine adjustment of a container's base without having to level the ground. When several supports are stacked, however, it is important to check that the assembly remains stable and that the supports are properly aligned.

On very soft ground, using a distribution plate or a bed of compacted gravel improves load-bearing capacity and prevents gradual sinking. The support can also be used to shim other heavy equipment, such as generators, site cabins or prefabricated modules, as long as the loads remain within the stated limits.

Compatibility with all ground types

A versatile support must be usable on earth, gravel, compacted sand, concrete, asphalt or pavers. However, the ground's load-bearing capacity directly influences the allowable load. On soft ground, the maximum load of 5.5 tonnes cannot be reached without risk of sinking. The working load of 2.1 tonnes is a more conservative reference for normal use, but it also assumes sufficiently stable ground.

For very soft ground, it is recommended to place a distribution plate under the support or create a bed of compacted gravel. This distributes the load over a larger area and limits sinking.

How to determine the number of supports needed

For a standard 20-foot container, four supports are generally sufficient if the ground is uniform. They are placed under the four corner fittings. For a 40-foot container or uneven terrain, additional supports may be useful to support the rails at regular intervals. A 40-foot container is more flexible and can deform if only the corners are supported.

The number of supports also depends on the load carried. A heavily loaded container will require finer distribution. It is advisable to provide at least one support every 2 to 3 metres along the rails, in addition to the four corners.

This product is sold individually, allowing the quantity to be adjusted as needed. The price of 38 euros per unit places this accessory in an accessible range, consistent with its protective and levelling function.

Best practices for installation and setup

Prepare the ground

Before placing the supports, it is essential to check the flatness and load-bearing capacity of the ground. Remove obstacles, protruding stones and vegetation. If the ground is soft, compact it or add a layer of gravel. For sloped ground, stacking supports can compensate for a slight incline, but it does not replace earthworks for significant slopes.

Position the supports

Place the supports under the four corner fittings of the container. For a loaded container, arrange the supports symmetrically and check levelness with a spirit level. A lack of levelness can make the doors difficult to operate and, over the long term, stress the structure. If additional supports are used under the rails, they must be aligned and of the same height.

Check stability

Once the container is placed, check that it does not tip and that the supports do not sink. On very soft ground, monitor gradual sinking in the days following installation. If necessary, add distribution plates.

Maintenance and service life

Maintaining the support is simple. Polypropylene is not affected by water and withstands pressure washer cleaning up to 80 °C and 200 bar. It is advisable to store the supports away from direct sunlight over long periods, not because the material melts, but because UV eventually alters the surface appearance of most plastics. Regular visual inspection helps identify cracks, deformations or abnormal wear that could reduce load capacity. A cracked or crushed support must be replaced, as its residual strength is no longer guaranteed.

After use in muddy terrain, rinsing with clean water is usually sufficient. For stubborn dirt, a pressure washer can be used within the stated temperature and pressure limits. It is not advisable to use aggressive solvents or wire brushes that could scratch the surface. Flat, stacked storage in a dry or sheltered location prevents deformation.

Comparison with other shimming solutions

Wooden supports are easy to find and inexpensive, but they rot on contact with moisture, attract insects and lose their mechanical properties over time. Concrete supports are very resistant to compression, but heavy, difficult to move and brittle on impact. Steel plates are strong but rust, slide on some grounds and can mark surfaces.

Polypropylene supports like this one offer an interesting compromise: lightweight, durable, unaffected by moisture, impact-resistant and recyclable. Their shape and material allow stable stacking, which is not always the case with heterogeneous materials. Their resistance to high-pressure cleaning is an asset for outdoor or dusty uses.

What supports do not replace

Supports are not securing devices. They do not replace straps, chains or twist-locks used to secure a container on a chassis or on a ship. Their role is limited to static placement on the ground. When a container must be transported, it must be securely lashed in accordance with road, rail or maritime transport rules.

The support is a passive safety accessory. It does not replace a soil study for heavy or permanent installations. For a container intended for regular use with heavy loads, it is recommended to consult a building or geotechnical professional to verify the ground's load-bearing capacity and size the base. In some cases, a concrete slab or concrete blocks will be preferable to supports, especially if the container is to hold heavy equipment, if it is stacked or if it is subjected to significant lateral forces.

Regulations and urban planning

Placing a container on private land generally falls under urban planning law. In France, a container used as a storage unit or dwelling may require authorization depending on its surface area, height and duration of installation. It is advisable to check with the local urban planning department before any installation. Supports do not exempt you from complying with local rules, but they facilitate installation in line with best practices, particularly regarding stability and safety.

For professional use, the employer must ensure that the installation does not present a risk of tipping or collapse, in accordance with the general prevention principles of the Labour Code. Particular attention should be paid to areas exposed to wind, where an empty container may be susceptible to overturning if the supports are not correctly arranged or if the container is not ballasted.

Sector-specific use cases

In the construction sector, site offices and welfare units are often installed on temporary, unstabilized ground. Supports allow a container to be placed quickly without pouring a slab, while providing a sufficiently stable base for personnel and equipment. In events, containers are used as ticket offices, dressing rooms, control rooms or technical rooms on sites that are not always prepared: lawns, sports fields, parking lots. Supports prevent damage to the ground and facilitate removal at the end of the event.

In agriculture and rural areas, containers are used to store grain, animal feed, equipment or plant protection products. Supports slightly raise the structure, limiting direct contact with damp ground and reducing moisture rising into the floor. In retail and logistics, containers serve as storage annexes or temporary sales points on parking lots or brownfield sites. Supports allow rapid installation, without construction work, and easy restoration of the site. Finally, for individuals, the support is useful for installing a garden container, workshop or storage unit on a lawn or slightly sloped ground.

Buying checklist

• Check the stated load: the maximum load on hard ground (5.5 tonnes) and the working load (2.1 tonnes) must be compatible with your use.
• Check flatness and absence of molding defects: a quality support has clean edges, a regular surface and uniform color. Recycled polypropylene supports may show slight color variations, without affecting their performance.
• Provide a sufficient number of supports: four for a 20-foot container on uniform ground, more for a 40-foot or uneven ground.
• Anticipate handling: a 6 kg support is easy to move, but storage space must be provided.
• Check compatibility with the ground: on soft ground, provide distribution plates.
• Ensure cleaning resistance: resistance to 80 °C and 200 bar is a plus for dusty or muddy environments.

Conclusion

Choosing a container support suitable for any ground type is based on a few simple criteria: dimensions, allowable load, material, stacking and ease of maintenance. The recycled polypropylene model measuring 40 × 26 × 45 cm, weighing 6 kg, with a maximum load of 5.5 tonnes on hard ground and a working load of 2.1 tonnes, meets most needs. Sold individually at 38 euros, it allows the quantity to be adjusted precisely and a container to be placed under good conditions on unprepared ground. Remember to check the ground's load-bearing capacity, comply with local urban planning rules and regularly inspect the condition of the supports.