Pallet stacking patterns: column vs interlock

How a carton carries load

A corrugated carton is strongest at its corners and vertical walls; the middle of the top panel is weak. When the corners of each carton sit directly on the corners below, the load runs straight down through the walls. When they do not, the walls bend and the carton loses a large part of its stacking strength.

Column stacking

Every layer is identical, so each carton sits squarely on the one beneath. This gives the highest compression strength and is the usual choice for heavy goods and tall stacks. The weakness is stability: columns can lean or separate, so use stretch wrap, strapping, corner boards or a top cap.

Interlocked (brick) stacking

Alternate layers are turned or shifted so cartons bridge the joints below, like bricks in a wall. The stack locks together and resists sliding, which helps for light cartons and short trips. The cost is strength: corners land on the weak middle of the cartons below, so heavy or tall interlocked stacks crush more easily.

Which should you use?

Overhang and underhang

Cartons that hang over the pallet edge lose support at their strongest point and are easily crushed by forklift tines or neighbouring pallets. Cartons that leave a large gap at the edge (underhang) can shift. Aim for the layer to cover the deck closely without overhanging.

Height limits

Plan the stack height from the tightest limit in the chain: racking beams at the warehouse, truck height, the container door (inside height about 2,393 mm in a 20GP or 40GP and 2,698 mm in a 40HQ, typical) or an airline's unit load device. Many sea shipments are stacked to around 1.6–1.8 m including the pallet.