Container shims for any ground: uses, conversions and possible fit-outs

Why shimming a container is a crucial step

A shipping container, whether used for storage, transport or fit-out, rests on four standardised corner blocks. These support points are designed to take all loads, whether during lifting operations or when set on the ground. However, on uneven, soft or sloping ground, these corners can sink, slip or create asymmetrical stresses. Over time, this can lead to structural deformation, difficulty opening doors, or even tipping risks. The container shim works precisely to distribute loads, level the whole and guarantee a stable footing, whatever the type of ground.

In this article, we explore the many uses of this recycled polypropylene shim, its possible conversions and the fit-outs it makes possible, whether you are a construction professional, a container park manager, a farmer or an individual wishing to install a housing module.

Uses of the container shim depending on the type of ground

The versatility of this shim lies in its ability to adapt to all types of ground, from the hardest to the softest. Here is how it behaves and what uses it allows in each configuration.

On concrete and asphalt

On a hard surface such as concrete or asphalt, the main risk is localised puncturing. The weight of the container, concentrated on the corner blocks, can mark the surface, or even crack it, especially if the surface is old or thin. The polypropylene shim, with its 40 x 26 cm bearing surface, distributes the pressure over a wider area. It thus prevents damage and ensures perfect stability. In addition, its non-slip surface prevents any accidental movement of the container, particularly in strong wind or vibrations.

On this type of ground, the shim is also useful for compensating for slight slopes. By stacking up to five shims, a slope of a few centimetres can be compensated without carrying out any work. This is a quick and economical solution for installing a container on a car park or existing slab.

On gravel

Gravel is a granular ground that tends to give way under a concentrated load. Without a shim, the container corners gradually sink, creating an imbalance. The shim, through its widened bearing surface, limits this sinking. It provides a stable base that prevents the container from sagging over time. For an optimal result, it is advisable to compact the gravel before installation and to check stability regularly, especially after heavy rain.

In a gravel container park, the use of shims makes it possible to store units without damaging them and to facilitate their later retrieval. Stackable shims also simplify storage when not in use.

On soil and soft ground

On natural ground, soil or recent backfill, the ground is often heterogeneous and has low bearing capacity. The container corners can sink by several centimetres, causing a loss of level and stresses on the structure. The polypropylene shim, thanks to its rigidity and width, limits sinking. It creates a stable bearing surface that keeps the container level.

For very soft ground, it may be necessary to supplement with a layer of compacted gravel or a distribution plate under the shim. This combination provides sufficient bearing capacity for most static installations. The shim then becomes a key element for installing a container on unstabilised ground, whether for a temporary site or long-term use.

Conversions and fit-outs made possible by reliable shimming

A correctly shimmed container opens the way to many conversions and fit-outs. With stability ensured, you can consider various projects, from simple storage to modular housing.

Secure and durable storage

For storage use, shimming is essential to protect your goods. A level container prevents water infiltration through doors and seals, as well as floor deformation. The shims also prevent direct contact between the metal and the ground, reducing the risk of corrosion. Whether for construction equipment, agricultural harvests or sensitive goods, a well-shimmed container guarantees optimal preservation.

In storage parks, shims make it possible to stack containers on several levels safely. The first row, perfectly stable, supports the weight of the upper units. Without adequate shimming, stacking would be risky and could lead to collapses.

Site office and living base

Containers are often used as site offices or living bases. On unstabilised ground, precise shimming is essential for doors and windows to work correctly. A level container prevents friction and malfunctions. The shims also make it possible to compensate for ground irregularities without earthworks, which speeds up installation and reduces costs.

In addition, a stable container is more comfortable for users and limits vibrations. This is an important aspect for living bases that must remain in place for several months.

Modular housing and permanent offices

Converting a container into housing or a permanent office requires a perfectly stable base. Shimming is the first step before any insulation, partitioning, plumbing or electricity. A level container facilitates the installation of utilities and guarantees the sealing of the whole. Polypropylene shims, durable and moisture-resistant, are particularly suitable for this type of project, as they do not rot and do not deform over time.

For housing, it is recommended to consult a professional to validate stability and comply with planning rules. Shims do not replace a soil study, but they are a practical solution for most grounds.

Events and temporary installations

In the events sector, containers are often installed on lawns, car parks or dirt ground. Shimming makes it possible to level the whole quickly without work. The shims are easy to transport and set up, which facilitates assembly and dismantling. They can be reused from one event to another, making them a cost-effective investment.

For temporary installations, speed of installation is a major asset. The shims stack and position in a few minutes, reducing preparation time.

Agriculture and equipment storage

In the agricultural sector, containers are used to store equipment, harvests or fodder. On waterlogged ground, the corners can sink and create an imbalance. The shims prevent this sinking and limit corrosion by isolating the container from the damp ground. They are also easy to clean, which is appreciated in a dusty or muddy environment.

For farms, the robustness and durability of polypropylene shims are important criteria. They resist common chemicals and freeze-thaw cycles, which extends their service life.

Possible conversions: beyond simple shimming

The container shim is not just a stabilisation accessory. It can be integrated into broader conversions to improve the installation.

Creating a levelling platform

By combining several shims and distribution plates, it is possible to create a levelling platform for a container on sloping ground. Stackable shims allow the height to be adjusted precisely, while the plates distribute the load over a larger area. This technique is useful for uneven ground where earthworks would be costly.

Integration into a light foundation system

For semi-permanent installations, shims can be used as a light foundation. They raise the container, facilitating air circulation underneath and reducing humidity. This can be supplemented with joists or beams to create a technical floor. This approach is common for containers fitted out as offices or housing.

Landscaping and visual integration

A container raised by shims can be integrated into landscaping. The shims can be concealed with wooden cladding or plants, while retaining access for inspection. This conversion makes it possible to integrate the container aesthetically into its environment.

Comparison with other shimming solutions

There are several alternatives to polypropylene shims: wood, rubber, concrete or metal. Each has its advantages and disadvantages.

• Wood: resistant to compression but sensitive to moisture, insects and fungi. Requires regular treatment and can rot.
• Recycled rubber: grippy and flexible, but crushes under very high loads and deforms in heat.
• Concrete: very resistant but heavy, difficult to move and can crack the surface.
• Metal: robust but can rust and scratch surfaces.

The recycled polypropylene shim offers a balance between rigidity, lightness and durability. It does not rot, does not rust and resists chemicals. Its stacking up to five units allows precise height adjustment, which few other solutions offer as simply.

How to choose and use your container shims

The number of shims required depends on the size of the container and the configuration. For a standard 20 or 40 foot container, four shims are enough, one under each corner. For longer containers or special modules, it may be necessary to use more or to supplement with distribution plates.

Before installation, make sure the ground has sufficient bearing capacity. On very soft ground, add a layer of compacted gravel. Position the shims under the corner blocks, ensuring they are flat. If you stack shims, check that the whole is stable and does not create any overhang. Finally, check stability regularly, especially after rain or frost.

For maintenance, cleaning with clean water or a high-pressure jet (up to 200 bar) is sufficient. Avoid aggressive solvents and metal tools. Inspect the shims before each use and replace them if cracked or deformed.

Regulations and safety

In France, installing a container for housing or office use may be subject to planning rules. It is advisable to check with the town hall. For transport, ground stabilisation shims are not approved securing devices. They must not be used to shim a container on a moving truck. For sea transport, containers are secured with twist-locks. Shims are only used for static storage on the ground.

On a site, an unstable container can cause accidents. Correct shimming contributes to worker safety and facilitates maintenance operations.

Common mistakes to avoid when shimming

Even with a suitable accessory, certain implementation errors can compromise the stability of the container. Identifying them in advance helps avoid costly problems.

Placing the shim anywhere other than under the corner blocks

The container is designed to transmit its loads to the four corner blocks. Placing a shim in the middle of a cross member or under the floor creates an unintended support point that can deform the structure. Always aim for the plumb of the corners, even if this requires slightly moving the whole.

Neglecting the bearing capacity of the ground

A shim does not make ground load-bearing: it distributes the load. On recent backfill or a marshy area, the ground must first be stabilised (compacted gravel, distribution plate) before placing the shims. Without this precaution, the whole sinks differentially and the container deforms.

Stacking without checking the level

Stacking up to five shims is practical, but each superposition must remain perfectly aligned. Even a slight offset creates a lever effect and weakens the base. A spirit level or rotating laser allows the horizontality to be checked after each adjustment.

Forgetting to check stability over time

Correct shimming at the time of installation can deteriorate after a rainy winter, a freeze-thaw episode or the passage of heavy machinery nearby. A seasonal visual check, with adjustment if necessary, is part of good operating practice.

How many shims to plan depending on the configuration

The number of shims depends on the type of container, its use and the ground. Here are some practical guidelines for sizing your order.

• 20 or 40 foot container installed alone: 4 shims, one per corner.
• Container installed on slightly sloping ground: 4 shims, possibly doubled or tripled on the downstream corners.
• Container stacked on two levels: 4 shims under the lower row, checking that the load per corner remains within the working limit.
• Reefer or flat rack container: allow a margin and check the load per corner, or even double the shims.
• Housing or office module with heavy equipment: add intermediate shims only if the structure allows it, otherwise reinforce the foundation.

If in doubt, it is better to oversize the shimming than to undersize it. An extra set of shims costs little compared with structural and safety risks.

Maintenance, durability and end of life of shims

Recycled polypropylene is a stable material that requires little maintenance. Periodic cleaning with clean water or a high-pressure jet is enough to remove mud, sand or hydrocarbon residues. It is not advisable to use aggressive solvents or sharp metal tools that could scratch the surface and create points of weakness.

For prolonged storage, it is preferable to stack the shims away from intense direct sunlight, even if the material remains UV-stable under normal conditions. A visual inspection before each reuse allows any cracks, deformation or abnormal wear to be detected. If a shim has a visible defect, it is prudent to replace it rather than use it under load.

At end of life, since polypropylene is recyclable, the shims can be integrated into a hard plastics recycling stream. This characteristic is part of a circular economy approach consistent with the prolonged use of the container itself.

Conclusion

The recycled polypropylene container shim is a simple but essential accessory for guaranteeing the stability and longevity of your container, whatever the ground. Whether you are a professional or an individual, it allows you to confidently consider various conversions and fit-outs. Available exclusively on our site, it is delivered with a video tutorial for correct implementation. Do not hesitate to contact us to determine the number of shims suited to your project.