Should cartons overhang a pallet or be set back from the edge? For most corrugated unit loads, cartons should be positioned close to the perimeter of the pallet without unintentionally hanging over the edge. Overhang can leave carton edges and corners unsupported, reducing compression strength and increasing the chance of product damage. Excessive setback, or underhang, isn’t necessarily better. The goal is to match the carton pattern and pallet footprint so the load uses the deck efficiently while remaining well supported.
It is a familiar palletizing problem. The case pattern doesn’t quite match the pallet. Let the cartons extend a little beyond the edge and everything fits nicely. Pull them back onto the pallet and you end up with unused deck space, or perhaps you can’t get as many cases onto the load. Pallet underhang can also create problems when loaded pallets are double-stacked.
So which is preferable? In most cases, deliberately overhanging corrugated cartons isn’t a great solution. But simply pulling everything well inside the pallet perimeter isn’t necessarily the answer either. The better approach is to look at the cartons, pallet and stacking pattern as parts of the same unit load.
Why Carton Overhang Can Be a Problem
Corrugated boxes derive much of their stacking strength from their vertical edges and corners. When a carton hangs beyond the pallet deck, part of that structure may no longer have the support it was intended to receive. The effect can be greater than it looks.
Research from Virginia Tech’s Center for Packaging and Unit Load Design has repeatedly demonstrated the interaction between pallets and the packages they support. Its work on pallet stiffness and corrugated box compression strength found that a flexible pallet deck deflects under load and creates uneven support beneath the boxes, concentrating pressure along box sidewalls instead of spreading it evenly. Boxes supported by high-stiffness pallets showed 29 to 35 percent greater compression strength than identical boxes on low-stiffness pallets. In other words, two loads using the same corrugated grade can have meaningfully different real-world strength depending on how the pallet beneath them supports the load.
That same unit-load principle applies when cartons aren’t fully supported by the pallet in the first place. The pallet isn’t simply something underneath the boxes. How it supports them can affect how the packaging performs.
This becomes particularly important in the lower layers of a tall load, where cartons are carrying the weight of everything stacked above them. Add high humidity or extended storage time, both of which can reduce corrugated strength, and a marginal support condition can become more important.
Overhanging cartons are also more exposed. When a pallet brushes a rack upright, another pallet or a forklift, the pallet itself would ideally take the incidental contact. With product hanging beyond the deck, the carton may get there first. Our companion article, How Much Pallet Overhang Is Too Much?, looks more closely at the clearance and handling problems created when the load extends beyond the pallet footprint.
Does That Mean Cartons Should Always Be Set Back?
Not necessarily. Leaving some pallet deck exposed can provide useful clearance and may be intentional in a properly designed unit load. But excessive setback, often called underhang, creates its own trade-offs.
If a 48×40-inch pallet is carrying a substantially smaller load, you’re moving unused pallet space through the supply chain. Multiply that by a trailer full of pallets and the lost cube can become significant. The same issue can affect warehouse positions and the number of pallets required to ship a given amount of product.
Pulling cartons inward also doesn’t automatically guarantee good support. A box may be completely inside the outside dimensions of the pallet and still bridge large gaps between deckboards. Pallet construction, deckboard spacing and pallet deflection all affect what is actually supporting the carton. This is one reason pallet capacity can’t be considered independently of the load and support condition, as discussed in How Much Weight Can a Pallet Hold?
This is also why the Virginia Tech Center for Packaging and Unit Load Design has long promoted a systems approach to unit-load design. The pallet, packaging and load-stabilization system interact. Optimizing one component without considering the others can simply move the problem somewhere else.
There are situations where exposed pallet decking creates concerns of its own. Retail display pallets are one example, where exposed pallet edges and deck area can create pedestrian hazards. We look at that issue separately in 4 Tips for Pallet Safety in Retail.
Sometimes the Real Problem Is the Case Pattern
Suppose a layer of cartons needs 41 inches of deck width but the pallet is 40 inches wide. Allowing half an inch of overhang on either side might seem like the easiest solution.
Before accepting it, however, ask why the pattern doesn’t fit.
Could the cartons be turned? Would a different layer pattern work? Has the case dimension changed while the pallet specification stayed the same? Is the product being placed on a standard 48×40-inch pallet simply because that is what the plant has always used?
There may be good reasons why none of those things can change. But recurring overhang is often a signal that the package and pallet specifications deserve to be looked at together. If pallet dimensions themselves are part of the question, see our guide to standard pallet sizes.
The reverse is also true. If a load consistently leaves several inches of unused pallet deck on every side, it may be worth asking whether the pallet is larger than the product really requires.
Neither question should be answered solely by trying to squeeze the greatest possible number of cartons onto a pallet. Package strength, pallet performance, load stability, material-handling requirements and transportation efficiency all have to survive the decision.
Think in Terms of the Complete Unit Load
There isn’t a universal rule requiring every carton to finish perfectly flush with every edge of every pallet. Products, packaging systems and distribution environments vary too much for that.
But unintended overhang deserves attention, particularly when corrugated cases are carrying significant stacking loads. Excessive underhang deserves a second look as well if it is wasting pallet deck and transportation cube. Underhang can also matter when loads are double-stacked, because the lower load and its packaging must safely support what is placed above it.
If the carton pattern and pallet footprint repeatedly don’t match, the best answer may not be deciding which imperfection to tolerate. It may be revisiting the unit-load design.
Use the pallet deck efficiently, keep critical carton structure properly supported and design the pallet and package to work together rather than treating them as two unrelated purchasing decisions.
Find answers to more questions about pallet overhang, load stability, pallet capacity and unit-load design at our Pallet Problems hub.
Rick LeBlanc, EMBA, is the founder and editor of Reusable Packaging News (subscribe to the free newsletter) and editor of Western Pallet Magazine. A supply chain journalist with more than 30 years of experience, he specializes in pallets, reusable packaging, material handling and related operations. Rick is co-author of Pallets: A North American Perspective and Pallets & Progress: A Collected History of Pallets and Palletized Handling 1922–1945. He is also an advisory board member of the Virginia Tech Center for Packaging and Unit Load Design. Read Rick’s full bio.