The container packing checklist a weighbridge can't argue with

Packing to the CTU Code means running seven checks before the doors close: verified gross mass, weight distribution, centre of gravity, segregation, securing, stack strength, and container condition. A container can be legally loaded yet make an illegal truck: most failures are where the weight sits, not how much.

The worst place to learn you packed a container wrong is a weighbridge in another country. The box left origin looking fine: doors shut, seal on, paperwork clean. Then a drive axle comes up two tonnes over on a road you’ve never driven, and now it’s a fine, a re-work under a crane you didn’t budget for, and a delivery that’s a day late because nobody looked at where the weight actually sat.

I’ve watched that happen more than once. It is almost never the amount of cargo that’s the problem. It’s the packing; packing is the one part of the journey still done largely from memory and a tape measure. This is the checklist I run before the doors close, framed around the rules cargo actually ships under.

What is the CTU Code?

The CTU Code, the IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units, is the international rulebook for stuffing a box. It isn’t a certificate you pass; it’s the standard everyone downstream is entitled to assume you met. When something shifts, crushes, leaks, or tips a truck, the CTU Code is the document the investigation opens first. Getting it right is cheaper than the alternative every single time.

The seven checks that decide whether a load moves legally: run them before the seal goes on.

The seven checks, in order

Verified gross mass. Weigh it: VGM is a legal figure, not an estimate.
Weight distribution. Spread the load and watch the axle at destination.
Centre of gravity. Keep it low and centred: heavy under light, never over.
Segregation. Keep IMDG classes apart, and decide the layout before placing anything.
Securing. Fill the voids and lash to EN 12195. Friction is not a plan.
Stack strength. Respect crush limits and don’t bury the fragile.
Condition and moisture. Start with a dry, sound box, and add dunnage and desiccant as needed.

The one that catches everyone: weight distribution

A container has a payload limit: a 40′ high-cube tops out around 26.5 tonnes. Stay under it and the box is legal. But the box then sits on a truck, and a truck is legal by axle, not by total. Push your pallets to one end to make loading easier and you can be comfortably under the container’s payload while the drive axle is over the road limit. Same tonnage, different verdict. The verdict that matters is the one at the roadside on the far side.

Identical weight. The only difference is where it sits. That's the difference between moving and being impounded.

The fix isn’t complicated, but it has to happen before the pallets go in: know each item’s weight, spread the heavy ones along the floor, and check the axle split against the limits at the destination, not just the origin.

Centre of gravity: low, centred, and actually calculated

The other quiet failure is height. A tall stack with the heavy items up top gives you a high centre of gravity, and a high CoG is what puts a box on its side on a roundabout or a ramp. The rule every experienced loader knows by feel, heavy low, light high, is really a CoG rule. The difference now is that you can put a number on it instead of trusting the feel.

Same items, stacked two ways. The dashed line is the centre of gravity: keep it in the lower third.

Then the rest of the list

Segregation is a decision you make before anything is placed, not a Tetris problem you solve after. IMDG separation between incompatible dangerous goods can’t be fudged once the pallets are in. If two classes have to stay apart, that governs the whole layout.

Securing is where “it looked tight” gets people. Friction alone typically holds only about a third of an item’s weight against sliding, so a snug fit is not restraint. Fill the voids, block and brace, and lash to EN 12195 loads, not to what feels solid by hand.

Stack strength is the crush limit nobody prints on the box: put the dense freight on the floor and keep it off anything that deforms. And the unglamorous last one, container condition and moisture: a sound, dry, watertight box, with dunnage and desiccant where the cargo or the voyage calls for it. Container rain has ruined more shipments than most people admit.

Do it in the plan, not by eye

None of this is new to a good loader. What’s new is that you no longer have to hold it all in your head at the doors. A load plan can carry the rules with it: VGM, the axle split, the centre of gravity, the segregation, the securing list. Then it hands your team a stuffing order they can actually follow, wall by wall.

That’s what we built LoadingMCP to do: right-size the container, place the cargo in 3D, and run the CTU, VGM, axle and centre-of-gravity checks as the plan is built. Then export a work order your warehouse and your carrier both read. You can plan it in the cockpit, or call plan_load from your own system and get the same answer. Either way the compliance is in the plan before the seal goes on; there are no surprises at the weighbridge.

If you want the shorter argument for why the rules belong in the plan rather than the post-mortem, we made it here: Packing to the CTU Code, not by eye.

Common questions about packing to the CTU Code

What is the CTU Code?

The CTU Code, the IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units, is the international rulebook for stuffing a container. It isn’t a certificate you pass; it’s the standard everyone downstream is entitled to assume you met.

What are the steps to pack a container to the CTU Code?

Run seven checks before the doors close: verified gross mass, weight distribution, centre of gravity, segregation of incompatible dangerous goods, securing to EN 12195, stack strength, and container condition and moisture. Sign only what you’d defend at the weighbridge.

Why can a legally loaded container still be an illegal truck?

A container is legal by total payload; a truck is legal by axle. Push the pallets to one end and you can be under the container’s payload limit while the drive axle is over the road limit: same tonnage, different verdict. Spread the heavy items and check the axle split against the destination’s limits.

What does “heavy low, light high” mean?

It’s a centre-of-gravity rule. A tall stack with the heavy items up top gives a high centre of gravity, which is what tips a box on its side on a roundabout or a ramp. Keep the dense freight on the floor and the centre of gravity in the lower third.