Stacking Strength: The Box That Holds the Pallet Together
Stacked pallets subject bottom boxes to the cumulative weight of everything above — which is why box compression strength (BCT) must exceed the stack load with a safety margin. Humidity, time, and handling all reduce that strength in the real world.
The Scenario: The collapse at the warehouse
A pallet of heavy goods collapsed after two weeks in a humid warehouse. The boxes passed lab compression at 65% RH but the warehouse ran at 85% — humidity had cut their stacking strength below the load.
Pain Points
- Stack loads are underestimated by counting layers, not dynamics;
- Humidity and time erode box strength after the lab test;
- Pallet patterns concentrate load on corners and edges.
The Solution: The stacking-strength equation
Box stacking design balances load against real-world derating:
1. Calculate stack load Layer count × box weight, plus dynamic handling factors, sets the required compression.
2. Derate for humidity High humidity can cut corrugated strength by 30–50% (corrugated industry data), so specify for the worst environment.
3. Design pallet pattern Column stacking concentrates load; interlocking patterns spread it but change the stress path.
The Result: Pallet integrity, verified
After re-specifying board for the humid warehouse and adjusting the pallet pattern, the collapse disappeared. Stacking strength is load math plus environmental honesty.