A customer once sent us a photograph of a pallet of bagged product where every bag in the bottom layer had a visible dip in the middle. The question was whether our pallets were defective. They were not: the platform was a five-board economy deck under a product that needed seven, and the bags were doing exactly what physics asks of them.
Two numbers that sound the same
Board count is how many deck boards there are. Deck coverage is what percentage of the footprint those boards actually cover. A seven-board deck of narrow boards can have lower coverage than a five-board deck of wide ones, and coverage is what the load feels.
A standard GMA 7/5 deck typically runs somewhere around 70 to 75% coverage. An economy 5/3 deck can be under 55%. Flooring-grade solid decks approach 100% and are used where product genuinely cannot bridge.
What bridging means
A rigid carton spans the gap between two boards and transfers its load to the board edges. That works fine until the gap exceeds what the case bottom can span. Then the base deflects into the gap, the carton loses its flat footing, and everything stacked above it starts to lean.
Rigid cases bridge well. Bagged product, soft-pack, loose-fill and anything with a flexible base bridges badly. Drums concentrate their entire load on four small contact patches, which is a completely different problem and the reason drum pallets use full perimeter support.
Matching coverage to product
- Rigid corrugated cases, well-stacked → 7/5 standard deck is fine and anything more is waste.
- Bagged product, sacks, soft-pack → you want higher coverage: nine boards, or narrower gaps, or a solid top deck.
- Drums and point loads → perimeter support and a reinforced deck; board count alone will not save you.
- Small-footprint items placed directly on the deck → high coverage or a slip sheet, otherwise individual items drop into gaps.
- Anything that gets wrapped tightly → remember that film compresses the load downward into the gaps, making bridging worse.
The economy-deck trap
Economy 5/3 construction is genuinely useful: light product, one-way shipments, short journeys. It is also the default cheap option that gets ordered on price for applications it does not suit, and the resulting damage is almost never attributed to the deck.
If you are seeing dished bottom layers, crushed bottom cases or unstable stacks that nobody can explain, measure your gap width before you blame the wrap, the loader or the carrier. The gap is usually the answer and it is the cheapest thing on that list to change.
Working out your own gap width
Measure the clear distance between two adjacent deck boards — not board width, the gap. On a standard GMA 7/5 deck that is typically around two to three inches. On an economy 5/3 it can be four inches or more. Then look at the base of your case or bag and ask whether it can span that unsupported.
For rigid corrugated cases the answer is almost always yes. For a 25 kg paper sack of powder the answer is no, and the sack will drape into the gap, and the layer above will sit on an uneven surface, and by the fourth layer the stack has a lean.
The three products that catch people out
- Bagged and sacked goods. No structural base at all. These want high coverage — nine boards, narrow gaps, or a solid top deck.
- Shrink-bundled units without an outer case. Common in beverage. The film holds the bundle laterally and does nothing for the base, so the bottom row of cans or bottles sits on board edges.
- Small-footprint items placed directly on the deck. Buckets, pots, nursery containers. Anything with a base narrower than the gap will simply fall into it, which sounds obvious and happens weekly somewhere.
Drums are a separate category: four 55-gallon drums concentrate their entire mass on four small contact patches, which is a point-load problem rather than a bridging one. That is why drum platforms use full perimeter support and a reinforced deck rather than simply more boards.
The wrap interaction nobody accounts for
Stretch film applied under tension does not only hold a load together laterally; it compresses it downward. A load that bridges acceptably when loose can be pulled into the gaps by aggressive wrap tension, and the resulting dishing gets blamed on the platform. If you have recently changed wrap machine settings and started seeing dished bottom layers, look there before you look at the pallet.
The cheapest fix, usually
A slip sheet or a fibreboard pad between the deck and the product. It costs very little, it spans every gap simultaneously, and it means you can keep buying the cheaper deck for a product that technically wants a dearer one. We suggest this to customers regularly and it costs us a sale of a higher-specification platform roughly every month, which is a reasonable price for the advice being correct.
Jonah, millwork · Pallets Recycle, 1113 Ingram Ave, Richmond VA · published July 30, 2024 · 827 words. Corrections welcome — tell us if we have this wrong.