How to stop cargo from shifting in a shipping container

When we first started exporting at Popsmalaya, one of our importers pulled me aside at Anuga (the world's biggest F&B trade fair) and complimented our warehouse team. He had received our container the month before. The cartons were stacked in straight rows, layer by layer, with no gaps. No shift damage. No crushed corners. He said our team clearly knew what they were doing.

That compliment made me proud. Maybe too proud. We had just started shipping internationally, and it was the first time a buyer had said something specific about how the cargo arrived, not just that it had arrived.

I think something jinxed it.

The next shipment to that same buyer, he called me when the container was opened on his end. The first box fell out of the door. We had missed the dunnage bags.

Here is what I have changed since, and why no container leaves our warehouse now without a written dunnage plan.

Five things this post covers

1. What dunnage actually is, and why F&B containers need it more than you would expect
2. The exact thing my warehouse team missed on the next shipment after Anuga
3. Why it was my mistake, not theirs
4. The dunnage plan I now write for every shipment
5. The free tool that does the dunnage maths for me

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What dunnage actually is

Dunnage bags are inflatable airbags that fill the void space between the cargo and the open side wall of the container. You inflate them after the cargo is loaded. They lock the cargo in place so cartons cannot shift during the eight to forty days it takes a container to reach destination.

Without dunnage, cargo moves. A loaded container goes through the dock, onto the ship, through swell on the open ocean, off the ship, and onto a truck. Every one of those steps puts side-to-side and front-to-back force on the stack. If there is space between the cartons and the wall, the stack slides into the space. If the stack slides far enough, the cartons closest to the door land against the door. When the importer opens the container at the other end, that is the box that falls out.

For light cargo like F&B, dunnage matters more than people expect. The lighter the cargo, the easier it is to shift. A pallet of ceramic tiles will sit where you put it. A pallet of biscuits, sauces, or snack bars will skid sideways with surprisingly little force.

What we missed at Popsmalaya

The shipment to that buyer was a standard 20ft of Popsmalaya. The carton count was right. The pattern on the floor was right. The total weight was inside the container's max payload.

What was wrong: our warehouse team had loaded the container, closed the doors, and not inflated any dunnage bags. There were two reasons.

The first: the dunnage bags were not on the loading checklist that I had written. The checklist had carton count, orientation, total weight, and seal number. It did not have a line that said: "inflate the dunnage bags between the cargo and the open side wall, spaced evenly along the length of the load."

The second: our team had not been told that dunnage was load-day instruction, not optional. They thought the bags were a "good idea if there is time", not a fixed step in the loading sequence.

Both came back to the same gap. The brief I had written did not list dunnage as a required step, and the team had not been trained on why dunnage was non-optional for F&B cargo.

Where the brief fell short

Our warehouse team at Popsmalaya is reliable. They stack cartons in straight, even rows. They handle product carefully. The Anuga compliment had come from a buyer with thirty years of receiving containers, so it was a serious one.

What they did not have was a written brief that listed the dunnage bags as a required step with a number and a position. Without that, the bags were treated as optional. When the loading window was tight (which it always is on shipping day), the optional step got dropped.

You cannot rely on a verbal "make sure to use dunnage" from the founder six months ago. That brief lives in someone's head, and someone is not always there on the day the container loads. The instruction needs to be on the piece of paper the warehouse team is loading from.

This is the lesson I tell every founder I talk to now. If a step is not on the loading checklist, it does not happen. If you do not put it on paper, it relies on memory. Memory is the most expensive way to manage a warehouse.

The dunnage plan I now write

Every container Popsmalaya ships now leaves with a one-page loading brief. The brief lives in a PDF that I send to our team the day before loading. It has:

1. Container type (20ft Standard, 40ft Standard, 40ft High Cube, reefer)
2. Carton dimensions, weight, and total quantity
3. Orientation (which way the cartons sit on the floor, with a diagram)
4. Stack height (how many layers)
5. Total weight against the container's max payload
6. A top-down diagram showing dunnage bag placement
7. The number of dunnage bags to inflate
8. A line that says: dunnage is a required step, not optional

That last line is the most important one on the brief. It tells the warehouse team that the bags are part of loading, not something to do "if there is time".

We added desiccant strips to the checklist around the same time. Desiccant absorbs moisture during the voyage. Tropical routes, which most F&B export lanes hit at some point along the way, are particularly humid. Condensation inside the container damages packaging and product. The strips are cheap. Skipping them is expensive.

Get a written loading plan for every container. Try the Container Loading Calculator →

What dunnage costs (so you can budget for it)

Inflatable dunnage bags run roughly USD 4 to USD 12 per bag, depending on size and material. A standard 20ft container loaded flush against one side wall typically needs two to four bags along the opposite void. A 40ft typically needs four to eight.

Desiccant strips are similar. A 20ft container with moisture-sensitive cargo (chocolate, biscuits, dried herbs, single-origin coffee) typically needs ten to twenty strips depending on the route climate. At roughly USD 1 to USD 3 per strip, that is USD 10 to USD 60 per container.

The total protection bill is small in every scenario I have shipped. A 20ft on a temperate route lands around USD 30 to USD 60. A 40ft on a tropical route with moisture-sensitive cargo can reach USD 200. Either way, it is under one percent of a typical shipment value. The cost of one box falling out, damaging product, and bruising the importer relationship is higher than that on every measurable axis.

The tool I now use to plan the load

I built the Container Loading Calculator because I did not want to keep opening a spreadsheet to work out carton fit, weight, dunnage, and desiccant for every shipment. You enter carton dimensions, weight, quantity, route climate, and moisture sensitivity. The calculator outputs:

1. Whether the order fits in a 20ft, a 40ft, or needs to split across two containers
2. The best carton orientation and how many stack layers fit
3. Total weight against the container's max payload, with corner-post deductions applied
4. The number of dunnage bags to inflate, with a top-down diagram showing where they go
5. The number of desiccant strips, based on cargo volume and route climate
6. A 3-page A4 PDF brief that goes straight to the warehouse team

The PDF is the brief I wish I had when we first started. It tells the team exactly what to load, in what orientation, how many cartons per layer, with how many dunnage bags at which positions, and how many desiccants. The "dunnage is required, not optional" line is on every brief the tool generates.

If you are an F&B exporter who has ever sent a container without a written loading plan, that PDF is what we now send our team the day before every shipment.

The Anuga compliment was for how our team stacked the cartons. But stacking neatly is only half of loading a container right. The other half is the written plan that lists every step, including the ones that are easy to skip. That is the part I now make sure is on the brief.

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Yasmin Karim is the founder of XportStack and Popsmalaya, a Malaysian freeze-at-home sorbet brand shipping to 35 countries across 6 continents over 8 years.