Packaging usually leaves us in good condition. What happens to it over the following weeks decides whether it still is when you use it. Most of the damage and nearly all of the mould we get asked about is created on the customer's own site, and it is cheap to prevent.
The five rules that prevent mould
Mould colonises wood above roughly 19% moisture content. Everything below follows from keeping packaging under that line:
- Store covered, dry, ventilated and well lit. All four matter — a covered but unventilated space traps evaporating moisture against the stack.
- Never store packaging in a trailer. This is the single most common mistake. A closed trailer is dark, warm and humid, which is a precise description of an incubator. Packaging parked in a trailer over a weekend can arrive at Monday visibly mouldy.
- Elevate stacks off the ground. Bottom boards standing in a puddle wick water upward through the whole stack. Bearers or a dry hardstanding solve it.
- Space rows for airflow, and orient pallet openings toward the air movement. Even a light draught helps significantly; a fan helps more.
- Remove stretch wrap immediately on receipt. Wrap is for transit. Leaving it on packaging that is still above 19% seals moisture against the wood and guarantees mould — this is the self-inflicted wound we see most often.
Add stock rotation to that list, and remove any mouldy material promptly, because it seeds the clean timber stacked next to it.
Fire — the part most warehouses get wrong
Idle pallet stacks are one of the more serious fire loads in a typical warehouse, and the codes treat them accordingly. A few points worth knowing even if you are not the person who signs the insurance:
- Outdoor storage is preferred. Insurer guidance actively favours keeping idle pallets outside the building, with separation distances from walls that vary by wall construction and stack size.
- In unsprinklered areas, the limits are strict: a maximum single stack of about 1.5 m, with at least 3.0 m between stacks. These apply regardless of pallet material.
- Plastic pallets are treated as a higher hazard than wood, with required outdoor separation distances roughly double. For stores above 200 pallets, that can mean 45 m from a combustible wall against 27 m for wood.
- Protection is based on the most severe pallet type present. This is the detail with real financial consequences: introducing a few plastic pallets into a wood-pallet warehouse can upgrade the sprinkler requirement for the whole area. If you are switching materials, talk to your insurer first.
One statistic circulates widely and is worth handling carefully: insurer loss data shows around 91% of idle-pallet fire losses involving wood and 9% plastic. That reflects population share — roughly 90% of pallets are wooden — not per-pallet risk. It is misused by both sides of the wood-versus-plastic argument.
The same data contains a more useful figure: where protection was adequate, the average monetary loss was about 12% of losses where protection was absent or ineffective.
Handling: where damage actually comes from
Almost all pallet damage is handling damage, not load damage:
- Forks entered at an angle split blocks and lever boards off. This is the leading cause.
- Dragging rather than lifting tears bottom boards.
- Dropping from height onto a hard floor cracks blocks that then fail later, under load, somewhere else.
- Storing outdoors on bare ground rots the bottom boards first.
If one site or one shift keeps producing broken pallets, the pallets are reporting a handling problem. It is usually cheaper to fix the handling than to keep replacing the pallets, and the damage pattern tells you which it is.
Stacking empties safely
Empty pallet stacks are unstable in a way loaded ones are not — there is no weight holding them together, and a stack that has been built by throwing pallets on top of one another leans. Keep empty stacks to a sensible height, square them up rather than letting them lean, and do not stack empties against racking uprights, where a collapse takes the racking with it.
For collars, one specific warning: only stack collars from a single manufacturer together. There is no European standard for collars, so tolerances differ between makers, and mixed stacks do not sit square.
A short receiving checklist
- Unwrap on arrival.
- Check a sample from different parts of the load, including a stack bottom.
- Move to covered, ventilated storage off the ground.
- Segregate anything showing mould or damage before it sits next to clean stock.
- Use oldest first.
None of that takes long, and it removes most of the reasons packaging fails to perform. If you are receiving packaging that arrives damp or stained repeatedly, tell us — the cause is sometimes at our end, and if it is, we would rather know.
