Egg Carton Pallet Patterns: Why the Fifth Layer Collapses

It Is Usually the Pattern, Not the Carton

A pallet that collapses in the middle of a stack usually has a pattern problem, not a carton problem. The cartons were strong enough individually.

Interlocked patterns transfer load through the carton walls rather than the posts, and the walls are much weaker in compression.

Changing the pattern costs nothing and often recovers more capacity than a board upgrade.

Column vs Interlock

Column stacking puts every carton directly above the one below, so load runs through the posts. It carries 30 to 50 percent more than interlocking for the same cartons.

Interlocking offsets each layer, which spreads load across the lid and the walls. It is more stable laterally but weaker vertically.

For cartons with well-defined posts, column stacking with strapping is almost always better.

Overhang and Underhang

A carton overhanging the pallet edge loses post support, and the overhanging corner carries almost nothing while the inner corner carries double.

A 25 mm overhang can cost 15 to 25 percent of stack capacity. Underhang is also a problem because the outer cartons then carry more than their share.

Match the pallet footprint to the carton footprint within 10 mm, and put a carton corner over each pallet corner.

Corner Boards and Strapping

Corner boards convert the outer layer into a load-bearing column and stop the stack from racking. They are cheap and effective.

Vertical strapping holds the stack together but does not add capacity unless it is tensioned against corner boards.

Strapping alone can crush the top layer if tensioned too hard. Tension is a setting, and it should be written down.

The Layer Where It Fails

Failure usually appears at the fourth or fifth layer from the top, not at the bottom. The bottom cartons are supported; the upper ones are the ones that deflect.

That is why a collapsed pallet often looks like a top-layer problem. The cause is cumulative deflection through the stack.

Measure the stack height after 24 hours. A gain of more than 3 percent means the stack is settling beyond its capacity.

Slip Sheets and Layer Pads

A layer pad between every fourth layer distributes load and reduces the deflection that leads to collapse.

Slip sheets help lateral stability but add a handling step. For a pallet that is machine-stacked, layer pads are usually the better choice.

Both add material cost and remove cartons from the pallet height. Calculate the trade, not just the pad price.

Verification

Load a pallet to the planned pattern and height, leave it 48 hours at the route humidity, and measure the height change and any lean.

Photograph the pallet from two sides. A lean of more than 10 mm over the height is a pattern or dunnage problem.

Record the pattern with the pallet number so a failure can be traced to the pattern used, not just to the carton specification.

Questions Buyers Ask

Which pallet pattern is strongest for egg cartons?

Column stacking, because load runs through the posts. It carries 30 to 50 percent more than interlocking for the same cartons.

Why does a pallet fail at the fifth layer rather than the bottom?

Cumulative deflection through the stack. The bottom cartons are supported while the upper layers deflect, so the failure looks like a top-layer problem.

How much capacity does overhang cost?

About 15 to 25 percent for a 25 mm overhang, because the overhanging corner has no post support.

Do corner boards help?

Yes. They turn the outer layer into a load-bearing column and resist racking. They are one of the cheapest capacity additions available.

How is a pallet pattern verified?

Load it, leave it 48 hours at route humidity, then measure the height change and any lean. A lean above 10 mm indicates a pattern or dunnage problem.

Next Step

Send the carton footprint, the pallet size and the stack height. You will receive a pattern recommendation with the expected capacity and dunnage, in one reply.

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