Ask a warehouse team why they interlock pallet layers and the answer is stability. It is a good answer and it is buying stability with a currency most people do not realise they are spending.
Where corrugated strength actually lives
A corrugated box carries vertical load almost entirely at its four vertical corners. The panels contribute, but the corners are the columns. This is why corner condition is weighted so heavily in grading and why strapping damage at a corner is so destructive.
Stack a box so its corners sit directly on the corners of the box below and the load path is continuous: column to column, all the way down. Offset it so the corners land mid-panel, and the panel below has to carry a load it was never designed for.
| Pattern | Strength retained | Stability | Typical use |
|---|---|---|---|
| Column (aligned) | Up to 100% | Low; needs wrap or banding | Heavy uniform loads into racking |
| Brick (offset rows) | ~60% | Good | Mixed weight, manual handling |
| Pinwheel | ~60 – 70% | Highest | Odd footprints with a centre void |
| Full interlock, alternating | ~45% | Highest | Light loads where toppling is the real risk |
The trade, stated plainly
Interlocking throws away roughly 55% of the compression strength you paid for, in exchange for lateral stability that stretch film and banding can also provide — and provide without the structural cost.
Column stack and wrap properly beats interlock and hope, almost every time.
When interlocking is still right
- Light loads where toppling, not crushing, is the actual failure mode.
- Manual handling where layers get removed one at a time and the stack must stay stable at every height.
- Loads with no wrapping or banding available at all.
- Mixed-weight pallets where the load path is irregular anyway.
The overhang multiplier
Pattern choice interacts badly with pallet overhang. A column-stacked box flush with the deck retains full strength. The same box with an inch of overhang loses around 30% before you have chosen a pattern at all, and interlocking on top of that leaves you with well under a third of the rated figure.
Which is why we keep saying the same thing: measure the pallets you actually own. A 48 × 40 GMA pallet in the real world runs from 47.5 to 48.5 inches. Specifying a container flush to 48 guarantees an overhang on half your fleet.
Practical sequence
- Measure your pallets. Not the standard — yours.
- Specify box dimensions flush to the smallest pallet you actually have.
- Column stack by default.
- Wrap with proper containment force, using corner boards so the film does not crush the corners you just protected.
- Interlock only where you have a specific reason, and know what it costs.
- If you need both strength and stability and cannot wrap, step up the wall construction rather than interlocking — it is usually cheaper than the 55% you were about to give away.
A note for reuse programmes
All of this matters roughly twice as much for reusable containers, because the damage is cumulative. A single-trip box that is 45% over-stressed survives its one journey. A pool container in the same position arrives back softened, gets graded down, and retires several trips early. Pattern discipline is one of the cheapest levers on trips-per-container there is.
Our pieces are written by the people who do the work rather than by a content agency, which is why they contain more numbers and fewer adjectives than is fashionable. If a figure here does not match your experience, we would genuinely like to hear about it — two of our published coefficients have changed that way.