Dunnage is any material placed in a trailer or container to keep cargo from moving, rubbing or absorbing shock in transit. It includes airbags, wood blocking, load bars, edge protectors, foam, kraft paper and honeycomb panels. It is not packaging — packaging protects an individual item, dunnage stabilizes the load as a whole.
Most container damage claims trace back to inadequate dunnage rather than rough handling.
Why loads shift
A container at sea is subject to rolling, pitching and heaving; a container on a chassis is subject to hard braking, potholes and lateral force in turns. Forward force under emergency braking is the largest single load case, and it is why the front bulkhead area and any void behind the last row of cargo matter so much. A 6-inch gap is enough for a pallet to build momentum and split a stack.
Types of dunnage
Air bags
Inflatable kraft or polywoven bladders placed in the void between pallet rows or between the cargo and the container wall. They are the workhorse of container loading — fast, reusable in some grades, and effective against lateral and longitudinal movement. They must be sized to the actual gap; an over-stretched bag will burst and a loose one does nothing.
Wood blocking and bracing
Lumber nailed or wedged to the container floor to fix heavy or irregular items in place. Essential for machinery, coils and anything with a high center of gravity. Note that any wood used as dunnage in international movements is subject to ISPM-15 treatment requirements — untreated blocking is a common reason a container is refused entry at destination.
Load bars and straps
Adjustable bars tensioned between trailer walls, plus ratchet straps and E-track. Standard in LTL trailers where the load is repeatedly opened and reconfigured at terminals.
Cushioning and separation
Foam, corrugated layer pads, honeycomb board, edge protectors under strapping, and slip sheets. These prevent abrasion and crush rather than movement, and they matter most for stacked or shrink-wrapped consumer goods.
Regulatory basis
In the United States, FMCSA cargo securement rules require that cargo be firmly immobilized or secured so it cannot shift or fall. The rules specify aggregate working load limits for tiedowns relative to cargo weight, and set commodity-specific rules for logs, metal coils, concrete pipe, vehicles and large boulders. For ocean containers, the CTU Code provides internationally recognised packing guidance, and carriers increasingly reference it in their liability terms.
The practical consequence: if a claim is filed and the load was packed without adequate blocking and bracing, the carrier will argue improper packing and the carrier liability defence usually holds.
Loading practice that reduces damage
- Load heavy items low and centered; keep the load balanced side to side within a few percent.
- Fill voids as you go rather than at the end. Voids at the door are the hardest to fill well.
- Do not rely on shrink wrap for stability. It holds a pallet together; it does not secure it to the container.
- Use edge protectors under every strap on cartoned goods.
- Photograph the load at three stages — front wall, mid-load, and at the doors before sealing.
- Record the seal number on the paperwork; the bill of lading is where a clean load record starts.
Dunnage and weight
Dunnage counts toward your gross weight. Airbags are negligible, but heavy wood blocking on a machinery load can add hundreds of pounds. If you are calculating verified gross mass by summing item weights, dunnage must be included in the total — omitting it is one of the most common VGM calculation errors.
Cost versus claim exposure
Dunnage for a typical container runs from a modest airbag spend to several hundred dollars for a full blocking and bracing package on machinery. Set against the value of the cargo and the cost of a contested claim, it is almost always the cheaper decision. Go Freight blocks, braces and documents every container it loads at its bonded Miami facility as part of its warehousing and cross-dock services.
Frequently asked questions
What is the difference between dunnage and packaging?
Packaging protects an individual item inside its own box or crate. Dunnage is the blocking, bracing and cushioning placed around and between items inside a trailer or container to stop the load as a whole from shifting, rubbing or absorbing shock.
Does wood dunnage need ISPM-15 treatment?
Yes, for international shipments. Any solid wood used as blocking, bracing, pallets or crating must be heat treated or fumigated and stamped with the ISPM-15 mark. Untreated wood dunnage is a common reason a container is refused or held at destination.
Does dunnage count toward container weight limits?
Yes. Dunnage is included in the gross weight of the container. If you are calculating verified gross mass by summing individual item weights rather than weighing the packed container, you must add the weight of all blocking, bracing and cushioning material.
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Go Freight is an asset-based Miami 3PL founded in 2004, running 100+ owned trucks, our own chassis pool, and a 104,000 sq ft bonded warehouse at 6901 NW 26 Ave, Miami, FL 33147. Request a rate or call (786) 445-0150.