Paper Pallets and Humidity: What Moisture Does and How to Plan

Published 26 October 2026 · By Ranjeet Kumar, Proprietor, Solution Enterprises

Short answer: paper absorbs moisture from the air, and the more it holds, the less load it carries. Humid air on its own is manageable if the pallet is sized with margin. Liquid water — rain, a wet floor, or condensation dripping inside a container — and repeated wet-dry cycles do most of the damage. Store paper pallets indoors and off the floor, keep them wrapped, ship them in dry containers, and do not plan on their dry-room rating in the monsoon.

What the research says

• Stability falls steeply. The CTU Code, the joint IMO/ILO/UNECE code for packing containers, says ordinary cardboard that is not waterproof loses up to 75% of its stability as humidity rises from 40% to 95%.
• It starts early. A Clemson University study of about 3,000 corrugated boxes found compression strength falling as moisture content rose, and notes that paper fibres are affected above roughly 30% relative humidity.
• Honeycomb behaves the same way. Laboratory work on paper honeycomb panels found dried samples resisting compression by up to 70% more than undried ones.
• Cycling is worse than steady humidity. US Forest Products Laboratory research linked repeated humidity swings to significant loss of compressive strength in loaded paperboard, and suggested a load level above which each cycle does progressive damage.

Put together: humidity does not make a paper pallet fail suddenly. It lowers the safe load, and long stacking under changing humidity lowers it further. The practical warning sign is creep: a stack that slowly leans, or feet that slowly shorten, over days rather than minutes. If a stored stack has started to lean, take the top units off before handling it, not after.

Moisture also reaches a pallet unevenly. Feet standing on a damp floor take up water long before the deck does, and the top of a load under a sweating container roof gets wet while the middle stays dry. That is why the response depends on the source of the moisture, as the table below sets out.

Three kinds of moisture, three responses

Exposure	What happens	What to do
Humid air	Slow uptake, gradual loss of strength	Size with margin; limit stacking time
Rain or wet floor	Fast local soaking, often at the feet	Cover, wrap, keep off wet ground
Container sweat	Drips from the roof onto the top of the load	Dry pallets, desiccants, top sheet

Inside a sea container

A closed container is a sealed box of air. The CTU Code explains that even dry dunnage, pallets and packing material hold about 12–15% moisture, and that this alone brings the air inside to around 60–75% relative humidity once the doors are shut. When the container cools at night or on a route to colder water, the steel roof cools first and moisture condenses on it — the “container rain” that soaks the top layer.

The Code gives useful thresholds: below 75% relative humidity prevents mould growth, and below 40% prevents corrosion. Its advice is to keep packing materials dry, avoid wet timber, pallets or packaging, and use desiccants together with sealed plastic wrapping where the cargo is sensitive. It also warns that plastic sheeting can promote mildew if the overall moisture inside is too high, so wrapping is not a substitute for loading dry. The same principles are covered for the whole load in how to pack pallets for sea freight containers.

Indian conditions to plan for

• Monsoon loading. Containers stuffed in the rain start their voyage already damp. Load under cover, or pause during heavy rain.
• Open-body trucks. A tarpaulin keeps off direct rain but not splash from the road. Wrap the full unit, pallet included.
• Floors and yards. Freshly washed floors and open yards wet the feet first, and the feet carry the load.
• Air-conditioned to outdoor. Moving a cool pallet into warm, humid air causes condensation on its surface, much like a cold glass.

The same season affects the rest of the load; see our guides on packaging for the monsoon season and edge protectors in monsoon humidity.

Storage rules for empty paper pallets

1. Store indoors, on a dry floor or on a raised base, never directly on concrete that is washed or sweats.
2. Keep stacks away from outside walls and roller shutters.
3. Leave the supplier’s wrap on until the pallet is needed.
4. Use the oldest stock first so nothing sits through a whole season.
5. Reject any pallet that feels soft, swollen or cool and damp to the touch.

Design for the wet case

Give a supplier the route, season and storage time along with the load, so the pallet is sized for its worst day. A higher grade, a thicker deck or more support under the load all buy margin. Moisture-resistant coatings exist, but ask what the coating is and whether your consignee can still recycle the pallet with paper waste; a buyer that chose paper for recyclability may not want a coated one. Our article on paper pallet load capacity explains how humidity interacts with each load rating.

We make honeycomb paper pallets to order. Tell us the route and the months you ship in on the quote form, and we will take humidity into account from the start.

Common questions

Are paper pallets waterproof?

No. Good ones resist humid air and brief splashes, but long exposure to water weakens any paper pallet. One maker states plainly that its pallets are not waterproof and should not be left exposed to water for long periods.

Will a paper pallet go mouldy at sea?

Mould needs sustained high humidity. The CTU Code puts the threshold at about 75% relative humidity, so dry loading, desiccants and a dry pallet keep the risk low.

Can paper pallets go into cold storage?

Cold rooms are often humid, and moving a cold pallet into warm air causes condensation. Use them there only after checking the design with your supplier for that exact cycle.

Sources

• IMO/ILO/UNECE, Code of Practice for Packing of Cargo Transport Units (CTU Code), 2014 — Annex 3 (condensation) and Annex 7 (packing and securing).
• G. A. Brown, Clemson University (2019), Relative Humidity Effects on the Compression Strength of Corrugated Boxes (MS thesis).
• S. Grigalinienė et al., Vadyba Journal of Management 38(1), 2022, Investigation of the Strength Properties of Composite Materials Based on Paper Honeycomb.
• D. E. Gunderson and J. M. Considine, USDA Forest Products Laboratory (1986), Measuring the mechanical behavior of paperboard in a changing humidity environment.
• PALLITE Group, Paper pallets: your questions answered.

Last verified: 26 October 2026. General guidance only. Humidity effects vary with design and materials; confirm the suitability of any pallet for your route and season.