Why stacking is the risky part
A full Gaylord can weigh a ton, and a stack of them stores enormous energy. When one gives way, it does so fast and heavy. Stacking is where most bulk-bin incidents happen, and nearly all of them trace back to a few ignored rules.
The good news is that those rules are simple, and following them prevents almost every failure.
Respect the wall rating
Every bin has a limit to how much weight it can bear stacked on top of it, driven by its wall count and edge-crush strength. The bin at the bottom of a stack carries everything above it, so the stack height must respect the bottom bin’s rating.
When you do not know the rating, be conservative. A double-wall bin is not a triple-wall bin, and stacking it as if it were is how columns collapse.
Heavy on the bottom, corners aligned
Corner alignment is the rule people cheat and regret. Corrugated is strong down its corners and weak across its panels. Offset the stack and you load the weak direction.
- Put the heaviest, strongest bins on the bottom of any stack.
- Align corners tier to tier so weight transfers straight down the strong vertical edges.
- Use lids or closed flaps between tiers to spread load and protect tops.
- Keep stacks plumb — a lean multiplies the force on one side.
“Load travels down through the corners. Misalign them and the panels take a force they were never meant to.”
Derate for the real world
Published strength assumes fresh, dry board in good condition. The real world is humid, and boxes age. Both reduce capacity, sometimes sharply — a bin that stacked safely when new and dry may not once it has absorbed a summer of humidity.
Build in a margin. Stack a little lower than the theoretical maximum, especially in unconditioned space or with boxes that have been in service a while.
The absolute no-gos
Never stack a bin that is crushed, out of square, or has been wet — its rating is gone even if it looks usable. Never mix a weak bin under a strong one. And never leave a leaning stack "to deal with later"; restack it or break it down now.
These are not bureaucratic rules. They are the difference between a routine day and a serious injury on the floor.