Column stacking keeps cartons vertically aligned from one layer to the next. Interlocking pallet stacking patterns change the relationship between adjacent layers, for example by alternating carton orientation so cartons bridge joints below.
The useful comparison is not simply “which fits more boxes?” A layer count, a carton’s ability to carry vertical load, and a pallet load’s resistance to movement answer different questions. This guide separates them with two original layouts you can reproduce.
Column stacking vs interlocking: what changes?
| Question | Column pattern | Interlocking pattern |
|---|---|---|
| How do layers relate? | The carton footprint repeats at the same positions. | Adjacent layers overlap differently through a changed arrangement or orientation. |
| What matters for compression? | Alignment of carton load-bearing edges and the support below them. | Where the upper cartons transfer load onto the cartons below. |
| What matters for stability? | The complete unit load, including its packaging and restraint. | The complete unit load; overlap alone is not a stability test. |
| Does the name establish capacity? | No. Validate the actual package and distribution conditions. | No. Validate the actual package and distribution conditions. |
A single layer viewed from above does not show the full stacking pattern. To distinguish the methods, compare at least two successive layers and identify which carton edges remain aligned.
Worked example: both patterns have 12 cartons per layer
Use an illustrative 120 × 80 cm pallet footprint and cartons with a 40 × 20 cm packed base. For this geometry example, assume zero clearance and no protrusions. Real measurements and handling allowances may change the result.
- Layer A: 120 ÷ 40 = 3 cartons along the length, and 80 ÷ 20 = 4 across the width: 3 × 4 = 12.
- Layer B: turn the carton footprint through 90 degrees: 120 ÷ 20 = 6 along the length and 80 ÷ 40 = 2 across the width: 6 × 2 = 12.
Each carton covers 800 cm². Twelve cover 9,600 cm², equal to the 120 × 80 cm footprint. Both layouts have the same nominal area coverage and no overhang in this drawing.
Column example: layer A followed by layer A
Repeating A keeps the same seams and carton positions on each successive layer. The diagrams are separate top views, not a drawing of cartons placed side by side on one oversized pallet.
Alternating example: layer A followed by layer B
The second layout changes the seams while keeping the same carton count. It is a simplified alternating-orientation example, not a catalogue of every interlocking pattern. Some boundaries still align; a pattern name does not tell you the support at every carton edge.
Download the original layer coordinates (CSV) to reproduce both examples. Each row gives the carton’s position and footprint in centimetres, measured from the same pallet origin. Carton numbers identify positions within each layer.
What the example proves: changing adjacent layers does not necessarily change cartons per layer. It does not prove equal compression strength, stability, permissible stack height or transport suitability. There is no physical test or strength model behind these drawings.
Why compression and lateral stability need separate checks
Compression concerns the package’s response to vertical load. Lateral stability concerns movement of the complete unit load during handling and transport. A geometry drawing measures neither.
FedEx’s freight packaging guide, page 4, discusses column stacking for top-to-bottom compression and makes its interlocking stability recommendation conditional on rigid carton contents. That condition matters: the goods and packaging inside a carton can affect how it supports a stack. The guide is a packaging reference, not a substitute for checking current service requirements for your shipment.
Do not turn a general comparison into a universal “100% strength retained” rule. The Fibre Box Association’s July 2021 research summary describes tests of specific box designs and board grades, comparing pallet stacking patterns with individual-box compression tests. Even aligned column stacks showed a reduction relative to the individual-box result. Those laboratory results do not supply an allowable load for a different carton.
What to establish before choosing a pallet pattern
Give the packaging or operations team a clear description of the proposed load, rather than only its TI value:
- Packed carton specification: dimensions, mass, construction, contents and applicable orientation or stacking instructions.
- Support: the actual pallet deck, gaps, carton edges and any overhang in the proposed arrangement.
- Layer sequence: the arrangement of each layer, the intended number of layers and the completed load height.
- Distribution conditions: expected storage and handling, environmental exposure and the relevant packaging validation.
- Unit-load preparation: the restraint and packaging procedure selected by the responsible team.
Use the team’s approved package and shipment requirements to decide what is acceptable. Neither a higher carton count nor more overlap is, by itself, approval to increase the load.
Use TI/HI and the free calculator for their actual purpose
TI counts cartons per layer; HI counts layers. For the terminology and height calculation, see Pallet TI HI Explained. Two loads can share the same TI and HI while arranging their layers differently.
The free pallet configuration calculator compares two uniform grid orientations for one carton size. It does not search interlocking or mixed-carton patterns, predict carton compression, or validate load stability. Use it to establish a geometric starting point and retain the separate packaging decisions.
For the broader workflow, review StowMetric pallet load planning. To discuss your cargo inputs and arrange a seven-day trial, contact the team.
Common questions
Does rotating a layer always change TI?
No. In the example above, the two orientations both give 12 cartons per layer. Other pallet and carton dimensions can produce different counts or gaps. Calculate with the packed dimensions and the allowances applicable to your load.
Does interlocking mean the pallet can carry more weight?
No capacity follows from the pattern name. A change that affects lateral movement can also change how cartons carry vertical load. Use appropriate package and unit-load validation for the actual configuration.
Can the free calculator generate an interlocking pallet plan?
No. Its two uniform-grid comparisons are not an interlocking-pattern search. The alternating-layer drawings in this article are original teaching examples, not output from an additional free-tool feature.