Container Loading and Stowage Guide: Weight Distribution, Securing and Moisture Control

Container loading and stowage is the step that most often decides whether cargo arrives intact, yet it is the one most frequently rushed. Ship motion, quayside cranes and hard braking on the road push cargo in every direction, and one badly placed pallet can put the whole box at risk. This guide gives you a practical checklist, from weight distribution and securing to moisture control and final checks.

Why container loading matters

A container travels by ship, through terminals, on trucks and sometimes by rail. At every stage the cargo is exposed to forces acting forwards and backwards, sideways and vertically. Poorly stowed cargo can slide, tip, crush or push against the container walls, damaging your goods and potentially neighbouring containers too.

The international reference here is the CTU Code (the IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units). It is not binding legislation but a code of practice; insurers, carriers and surveyors nevertheless treat it as the benchmark for good practice. Following its principles also strengthens your position if a damage claim is ever disputed.

Choose the right container and inspect it

Loading starts the moment you receive the empty box. Check our container types page to pick the right equipment for your cargo. Before loading, inspect the container for:

CSC plate: the Safety Approval Plate must be present and valid. It shows the maximum gross mass and the tare (empty) weight.
Structural condition: no holes, cracks or major dents in walls, roof or floor. If you can see daylight from inside with the doors closed, water can get in too.
Cleanliness and odour: residues, dust or smells from previous cargo can ruin food, textiles and other sensitive goods.
Floor and lashing points: the timber floor should be sound and the lashing rings intact.
Doors and seals: doors should open and close smoothly, and the rubber gaskets should be undamaged.

Photograph any defect and ask for a replacement straight away; objecting after loading has started is much harder.

Weight distribution and centre of gravity

The golden rule of container loading is to spread the weight evenly across the floor and keep the centre of gravity low and as close to the middle of the container as possible.

Heavy at the bottom, light on top: place heavy, robustly packed items on the floor and lighter or fragile items above.
Lengthwise balance: do not concentrate weight at one end. A box that is heavy at the front or rear causes problems for cranes and for truck axles.
Side-to-side balance: avoid a noticeable weight difference between left and right.
Concentrated loads: for machinery or other items that put a lot of weight on a small area, spread the load with timber beams, or the floor may be damaged.
Maximum mass: cargo, packaging and securing material together must not exceed the payload shown on the CSC plate. On the road leg, national axle and gross vehicle weight limits also apply.

Loading sequence for mixed cargo

If you are packing items of different sizes and weights into one box, decide the loading sequence in advance. Think about unloading too: goods that must come out first at destination should be near the doors. Keep containers of liquids in a separate section, upright and never above dry cargo, so a leak cannot spread. Avoid shipping goods that can transfer odours (chemicals and food, for example) in the same container. Always respect "this way up", "do not stack" and maximum stacking height markings; if the bottom carton's strength is exceeded, the whole stack collapses.

To visualise the layout before loading, try our 3D load planner, and work out volume and weight in advance to avoid surprises on loading day.

Securing (lashing) and filling voids

The most common mistake is assuming that "the box is full, so nothing can move". Even a gap of a few centimetres lets moving cargo build up momentum and hit with real force.

Securing methods

Blocking: stopping movement by bracing cargo against the container walls or against other cargo, typically with timber chocks and frames.
Lashing: tying cargo to the container's lashing points with ratchet straps, steel wire, chains or textile belts. The working load of the lashing material must suit the cargo.
Increasing friction: anti-slip mats reduce sliding on the floor but are not enough on their own.

Dunnage

Dunnage is the general term for materials used to fill gaps, support and protect cargo: timber, plywood, cardboard, inflatable airbags and foam. Keep in mind:

Airbags must be inflated to the right pressure and kept away from sharp edges.
Cargo must not lean against the doors; build a barrier at the door end so nothing falls out when the box is opened.
Wooden packaging and pallets used in international shipments must meet the destination's plant health rules, usually ISPM 15 heat-treated and marked.

Moisture and condensation (container rain)

Moisture inside the box condenses on the roof and walls as temperatures change, a phenomenon known as container sweat or "container rain". Droplets fall onto the cargo and cause mould, rust, damaged labels and collapsing cartons. The risk is highest on long sea voyages between hot and cold climates.

To reduce condensation:

Keep cargo and packaging dry and avoid loading in the rain.
Do not use damp timber pallets or dunnage.
Use desiccant bags or strips where needed.
Protect sensitive goods with moisture-barrier packaging or stretch film; covering the top layer with paper or sheeting adds protection against dripping.
For temperature-sensitive products, consider a reefer or ventilated container.

Dangerous goods and special cargo

For dangerous goods, the rules on packing, segregation, labelling and documentation are much stricter, and sea transport falls under the IMDG Code. Check your product's class on our dangerous goods classes page and always confirm with your forwarder before booking. Heavy machinery and out-of-gauge cargo usually need flat rack or open top equipment and a dedicated securing plan, which we plan separately as project logistics.

Post-loading checklist

Record the total weight of cargo, packaging and securing material; you will also need it for the VGM (Verified Gross Mass) declaration.
Photograph the loading stages and the final view before the doors are closed.
Close and seal the doors, and match the seal number with the load list and shipping documents.
Make sure the packing list matches exactly what is in the container.

Frequently asked questions

Is compliance with the CTU Code mandatory?

The CTU Code is not binding legislation in itself; it is a code of practice issued by the IMO, ILO and UNECE. Because it is used as the benchmark in damage and insurance cases, following it is strongly recommended.

If the container is completely full, do I still need securing?

Yes. Even a tightly packed box needs measures at the door end and on the upper layers. Small gaps should be filled with dunnage or airbags.

Is damage from container sweat covered by insurance?

It depends on your policy and on the cause of the damage. Losses caused by inadequate packing or poor stowage may be excluded, so discuss the details with your cargo insurance adviser.

Who should prepare the load plan?

The shipper (exporter) is usually responsible for packing. Getting planning support from your forwarder significantly reduces errors, especially with mixed or heavy cargo.

At Medius we support your FCL shipments before loading with container selection, load planning and securing advice. See our sea freight page or send us a quote request.