Non-Stackable Cargo: What Cannot Be Stacked During Transport

When calculating the cost of international shipping, it’s important to know more than just the weight, volume, and number of pallets. Another factor that affects cargo placement and shipping costs is stackability.

Two pallets of the same size and weight can take up different amounts of space in a truck. If one pallet can be placed on top of another, the cargo area is used more efficiently. If the cargo cannot be stacked, the space above it cannot be used.

This is especially important when transporting consolidated shipments, where goods from multiple shippers are loaded onto a single vehicle.

Let’s examine which types of cargo cannot be stacked, whether pallets containing hazardous materials can be placed on top of one another, and why stacking restrictions must be taken into account before booking transportation.

What Is Cargo Stacking?

Stacking is the placement of cargo units on top of one another in multiple tiers. This method allows for more efficient use of space in a truck, container, or warehouse. However, the lower cargo unit must be able to support the weight of the one above it without deforming the packaging, damaging the goods, or losing stability.

Cargo can be broadly divided into three categories:

• stackable—other cargo may be placed on top;
• conditionally stackable—there are restrictions on load capacity or the number of tiers;
• non-stackable—placing cargo on top is prohibited.

Important: A standard 1200 × 800 mm Euro pallet does not, in and of itself, mean that the cargo can be stacked. What matters are the properties of the goods, the packaging design, and the permissible load.

What Cargo Cannot Be Stacked

There is no universal list of non-stackable goods. The same cargo in different packaging may have different restrictions. However, there are several categories for which the issue of stacking is particularly important.

Fragile Cargo

Glass, ceramics, optics, instruments, electronics, and other sensitive goods may not withstand vertical loads. Pressure from the pallet above is transmitted through the packaging and can lead to deformation of boxes, damage to protective elements, or damage to the goods themselves.

That said, fragile cargo is not always non-stackable. If rigid transport packaging with sufficient strength is provided, a second tier may be permitted. Therefore, one must rely on the packaging specifications and the manufacturer’s labeling.

Industrial Equipment and Machinery

Machine tools, pumps, electric motors, production units, and other equipment are often transported on pallets or in wooden crates.

When transporting industrial equipment, it is necessary to consider not only the strength of the outer packaging but also its design.

For example, a wooden crate may look sturdy, but its top is not necessarily designed to support the weight of another pallet. If the equipment is secured on an open pallet and there is no rigid supporting structure on top, another load cannot be placed on it without an additional load-distribution solution.

Cargo in Cardboard Boxes

Cardboard boxes may only be stacked within the load limits that the packaging can withstand. The weight of the top tier, the quality of the cardboard, the arrangement of the boxes, and the even distribution of pressure are all important factors.

For example, a tightly packed pallet with identical boxes can withstand a vertical load. However, if the boxes are of different heights or the pallet is not fully filled, the top tier may damage the packaging.

Cargo in flexible packaging

Bags, big bags, and certain types of polymer packaging can deform under load. If a heavy load is placed on top, the lower tier may deform, and the entire stack may lose stability. The feasibility of such placement depends on the characteristics of the specific packaging and cargo.

Pallets with Overhanging Cargo

If the cargo extends beyond the pallet’s edges, the load from the top tier may be transferred directly to the cargo rather than to the supporting structure. This increases the risk of damage and compromises the stability of the stack. This situation often occurs when transporting metal parts, structures, and equipment of non-standard dimensions.

Non-standard and oversized cargo

Coils, rolls, metal structures, long parts, and irregularly shaped cargo typically require a customized placement plan.

When transporting oversized cargo, special frames, cradles, or other support structures may be used to create multiple levels. Without such preparation, cargo cannot be considered stackable simply because it is capable of withstanding a heavy load.

Liquids in Barrels and Canisters

Liquid cargo is not automatically non-stackable. Barrels, canisters, and other containers can be stacked in multiple tiers if the packaging is designed to withstand the corresponding load.

Otherwise, pressure may cause the container to deform, damage the sealing elements, or compromise the container’s airtightness. Particularly serious consequences are possible when transporting chemical products.

Can ADR hazardous cargo be stacked?

Hazardous cargo does not automatically preclude stacking. If the containers comply with the applicable requirements and are designed for multi-tier stacking, hazardous cargo may be stacked.

The requirements regarding this matter are set forth, in particular, in subsection 7.5.7.2 of the ADR. Packages must not be stacked unless they are designed for that purpose. When loading different types of packages together, their compatibility must also be taken into account.

If necessary, spacer boards or other solutions are used between layers to distribute the load and protect the lower packages. Therefore, when transporting ADR dangerous goods, not only the hazard class of the substance is taken into account, but also the type of container, its marking, permissible load, and stability.

Simply put: ADR cargo is not necessarily non-stackable. The decision is made on a case-by-case basis for a specific cargo and specific packaging.

Can IBC containers be stacked?

IBCs are widely used for transporting chemical cargo, so the ability to stack them is particularly important. This must be determined based on the marking of the specific container.

For IBCs intended for stacking, the maximum permissible top load is specified. If the design is not intended for stacking, the corresponding marking indicates that stacking is prohibited, and the test load value for such a design is specified as “0.”

The presence of a metal cage around the tank does not in itself mean that another IBC may be placed on top of it. Before loading, it is necessary to check the markings on the packaging being used.

How is cargo marked as non-stackable?

Transport packaging may bear the marking “Do Not Stack,” indicating that other cargo must not be placed on top. Markings indicating the maximum permissible load during stacking are also common.

However, the absence of a prohibition symbol does not automatically mean that the cargo can be stacked in multiple tiers. If the permissible load is unknown, you must verify this information with the manufacturer, shipper, or packer.

This is especially important for expensive equipment, chemical products, IBCs, and non-standard cargo.

Can Different Pallets Be Stacked on Top of Each Other?

Even if both pallets are designed for stacking, you must verify their compatibility.

For example, a small, heavy wooden crate placed on a pallet with cardboard boxes can create excessive point loading.

Therefore, the following factors are considered:

• the weight of the upper layer;
• the contact area;
• the strength of the lower packaging;
• the center of gravity;
• the stability of the structure.

If necessary, spacer boards and separation materials are used to distribute the load.

Why non-stackable cargo can cost more

The ability to stack cargo directly affects the amount of space it occupies in a truck.

Consider a pallet measuring 120 × 80 × 80 cm and weighing 300 kg.

If a second pallet can be placed on top, the carrier uses the cargo area in two tiers. If the cargo is non-stackable, the space above it may remain empty all the way up to the semi-trailer’s roof.

This particularly affects the cost of delivering consolidated shipments from Poland. In LTL shipping, it’s not just the physical volume of the cargo that matters, but also the floor area it occupies. Therefore, two pallets that are identical in size and weight may have different shipping costs.

Example: Why Volume Alone Isn’t Enough

Let’s say you need to ship four pallets:

120 × 80 × 100 cm — 4 loading units.

Total physical volume:

4 × 1.2 × 0.8 × 1 = 3.84 m³.

If the pallets can be stacked in two tiers, the four cargo units will potentially occupy the floor space of two pallets. If all four pallets are non-stackable, each must be placed separately on the floor.

This means that, for the same volume and weight, the required cargo space can differ by nearly a factor of two. This is precisely why, when requesting a quote, it is not enough to simply provide the carrier with the cubic volume.

What to Provide to the Logistics Specialist Before Calculating the Shipment

For an accurate cost calculation, it is advisable to provide the following information right away:

1. the number of cargo units;
2. the dimensions of each unit;
3. the weight of each unit;
4. the type of packaging;
5. stackability;
6. the maximum allowable top load, if known;
7. photos of the cargo;
8. ADR information;
9. loading and unloading requirements.

For equipment and non-standard cargo, photographs are particularly important: they allow you to identify protruding elements and potential placement restrictions in advance.

The main rule for stacking cargo

Stackability cannot be determined based on the assumption that “if the packaging looks sturdy, it will hold up.” It is essential to consider the characteristics of the goods, the packaging design, the permissible vertical load, labeling, and transportation conditions.

Fragile goods, equipment, non-standard cargo, liquids, chemical products, and ADR and IBC dangerous goods should be checked with particular care.

If reliable information is unavailable, it is best not to plan to place another shipment on top until confirmation is received from the shipper or manufacturer.

Properly determining stackability helps protect goods from damage, select appropriate transportation, and accurately calculate the cost of international freight.

FAQ

What types of cargo cannot be stacked?

Restrictions most often apply to fragile goods, equipment, non-standard cargo, and products in packaging that is not sufficiently sturdy or is prone to deformation. However, there is no universal list: stackability is determined on a case-by-case basis for each specific cargo and its packaging.

Can pallets be stacked?

Yes, if the goods and packaging are designed to withstand the corresponding vertical load. The standard size of a Euro pallet alone does not confirm that it can be stacked.

Can ADR dangerous goods be stacked?

Yes, if the packaging is designed for stacking and the applicable ADR requirements are met. The fact that a shipment is classified as dangerous goods does not in itself prohibit stacking in multiple tiers.

Can IBCs be stacked on top of each other?

Only if the specific IBC is designed for stacking. You must check its markings and the maximum allowable top load.

Why might non-stackable cargo cost more?

Because the space above it cannot be used to store other goods. In consolidated shipments, this increases the floor space required for the shipment.