The 30% rule: overhang, and why your cases crush
In short
Corrugated cases carry load through their vertical corners. When a case overhangs the pallet deck, its corner has no support beneath it and transfers weight onto the case below instead, which was not designed to take it. The commonly cited penalty is around 30 percent of stacking strength, and it compounds with every layer of the stack.
Talk to us about this
If this piece describes a problem you actually have, describe it back to us in the message field. You will get a written answer from a person within one business day.
Why a corrugated case cares
A corrugated box carries almost all of its compression strength in the four vertical corners. The panels contribute very little. Place a case so that a corner sits over the deck and it transmits its load straight down through the pallet into the floor or the rack beam. Place it so the corner hangs past the deck edge and that load has nowhere to go but sideways and down into whatever is beneath it.
In a stacked configuration, "whatever is beneath it" is the top panel of the case below — the weakest part of that box. The damage shows up two or three layers down and looks like a case failure, which is why it so often gets reported as a packaging quality problem.
Spotting it
- Look along the deck edge at eye level. Any case that shades the edge is overhanging.
- Crushed corners appearing consistently on the same side of the load point to a pattern problem, not random handling.
- Damage concentrated in the bottom third of a stack, worsening downward, is the classic overhang signature.
- If the stretch wrap shows a taut line along the pallet edge and slack above it, the load is wider than the deck.
- Ask receiving where the damage lands. They know, and nobody ever asks them.
What actually fixes it
| Situation | Fix | Not a fix |
|---|---|---|
| Load overhangs 48×40 by 1–3 in on the long side | Move to 48×48 or a custom footprint | Heavier corrugate |
| Load overhangs on all four sides | Purpose-built footprint sized to the load | More stretch film |
| Four drums on a rectangle | 48×48 square | Blocking and bracing |
| Bulk bag slumping past the edge | 48×48, or a bag restraint frame | Accepting it |
| Occasional overhang from mixed SKUs | Pattern change, or a top cap and corner board | Telling the loaders to be careful |
Appendix: the data behind this
Every piece on this site closes with the slice of our operating record that bears on what it argues. The full record is published at /resources/operating-record.
Derating factors, with overhang at the top
Thirty percent is the largest single penalty in the table, and it is the one most often accepted without anybody deciding to accept it.
| Condition | Effect | Why it happens |
|---|---|---|
| Load overhangs the deck edge | −30% unit-load stacking strength | Case corners lose their support and transfer load into the layer below. |
| Moisture content above 25% | −15 to −20% strength | Wet cell walls deflect further under the same load. |
| Racked storage beyond 90 days | −25% (creep allowance) | Permanent, progressive deflection under sustained load. |
| Concentrated point load | −20 to −40% | Depends entirely on whether the point sits over a stringer or over a gap. |
| Companion-repaired stringer | −10 to −20% bending | The crack is bridged, not healed. Fine on a floor; not in a rack. |
| Fork entry through the notches | −30 to −40% in that direction | Material removed at the point of highest bending stress. |
| Unit load not stretch-wrapped | −10 to −25% stack stability | The film is a structural member. Most people do not think of it that way. |
| Storage below freezing | Stiffness up, impact resistance down | Cold wood fractures where warm wood would bruise. |