At a glance:

• Mould grows when timber pallets are exposed to moisture, warmth, and poor ventilation.
• Regular inspections help identify discolouration, odour, and texture changes that signal mould growth.
• Proper storage, ventilation, and heat treatment are key to preventing mould formation.
• If mould appears, isolate, clean, or decommission affected pallets to protect your shipments.

Mould may seem like a minor concern compared to mechanical damage or handling errors, but in logistics and warehousing, it poses one of the most persistent and overlooked challenges. When pallets become damp or poorly ventilated, microscopic mould spores find ideal conditions to grow and spread.

Beyond the visible surface issue, mould contamination can jeopardise product integrity, disrupt shipping timelines, and even damage a business’s reputation, particularly when hygiene and product integritye are at stake.

This article explains why mould grows on wooden pallets, how to detect it early, and what preventive measures and treatment steps can protect your supply chain.

Why Mould Grows on Wooden Pallets?

Wood is a natural, porous material made up of cellulose fibres, which serve as an ideal food source for mould spores. When these spores land on damp wood and find warmth and low airflow, they quickly multiply, leading to visible discolouration, odour, and gradual structural decline.

In industrial environments, a combination of humidity, temperature fluctuations, and poor ventilation creates the perfect conditions for growth. Some of the most common triggers include:

• Prolonged exposure to humidity or rain, particularly when pallets are stored outdoors or uncovered.
• Poor airflow in warehouses where pallets are stacked too tightly or placed against walls.
• Inadequate drying after washing or treatment, which traps moisture between boards.
• Stacking wet or freshly treated pallets, preventing natural evaporation.

Untreated timber is particularly susceptible because it retains more natural moisture than heat-treated or kiln-dried wood. Heat-treated pallets go through a controlled drying process that drives out internal moisture and kills pests, making them much more resistant to mould.

In Australia, environmental factors add an extra layer of risk. Coastal humidity, combined with condensation in enclosed warehouses during cooler months, can quickly turn stored pallets into breeding grounds for mould. For companies operating in regions like Melbourne, New South Wales or Queensland, where coastal humidity and seasonal condensation are common, mould prevention should be viewed as a core part of pallet maintenance, not an afterthought.

How to Detect Mould in Wooden Pallets?

Early detection is key to preventing mould from spreading across multiple pallets or compromising stored goods.

Below are the most reliable and practical ways to identify mould early and keep your pallet stock safe for ongoing use.

Visual and Physical Indicators

Look for black, green, or white fuzzy patches on the pallet’s surface, particularly along deck boards and stringers where moisture collects. These are the most common indicators of surface mould. Sometimes the wood may appear stained, darkened, or patchy without visible fuzz, which is an early sign that mould is beginning to develop below the surface.

Run a hand across the surface to check for unusual texture changes; wood that feels soft, slightly damp, or uneven may be holding moisture. Mould can also cause a thin powdery layer or fine dust-like residue that wipes off easily.

Odour and Hidden Moisture Signs

A strong, musty or earthy odour is one of the most reliable warning signs, especially in enclosed storage areas. If a smell persists even after cleaning, it often means the spores have penetrated deeper into the timber fibres.

For more advanced operations, UV light scanning can help reveal early mould presence on dark or treated wood, while moisture meters provide quick readings of internal humidity levels. A moisture content above 20% typically indicates conditions where mould growth can begin.

Routine Inspection

Effective mould detection depends on consistent and disciplined inspection. Build inspection routines into the pallet cycle whenever units are returned, loaded, or restacked. Encourage warehouse teams to make quick visual and odour checks during handling, especially in humid or wet conditions.

A regular inspection schedule helps prevent isolated mould issues from spreading across inventory. Identifying a problem early protects product quality, keeps shipments moving, and avoids costly delays or quarantine incidents. In busy warehouse environments, even a few affected pallets can disrupt the entire supply chain.

How to Prevent Mould in Wooden Shipping Pallets?

Preventing mould is far more effective and economical than treating it later. A few disciplined and well-managed practices can make wooden shipping pallets significantly more resistant to moisture, bacteria, and biological decay.

Use Heat-Treated Pallets

Heat-treated pallets meet ISPM 15 international standards, which require heating to at least 56°C for 30 minutes to eliminate pests and reduce fungal and mould risk by removing internal moisture. This process leaves the timber drier and more stable, making it ess likely to develop mould. These pallets are ideal for export operations and domestic warehousing that require a more hygienic, long-lasting solution.

Maintain Airflow and Ventilation

Good airflow prevents humidity from being trapped between stacks. Avoid stacking pallets too closely or directly against walls. In enclosed warehouses, install fans, vents, or dehumidifiers to maintain balanced air movement. Periodic rearrangement of pallet stacks helps air circulate to the lower levels, where moisture tends to accumulate.

Store Pallets Off the Ground

Ground moisture can seep upward into timber, especially when pallets rest on soil or unsealed concrete. Storing pallets on racking, bearers, or elevated platforms prevents contact with damp surfaces and allows airflow underneath. This small adjustment dramatically reduces the risk of moisture absorption, which is a key factor in proper pallet storage and handling.

Clean and Dry Properly

Washing pallets can help maintain hygiene, but if they are not fully dried afterwards, the residual water may encourage mould growth. Always allow pallets to dry completely in sunlight or under controlled airflow before reuse. Avoid high-pressure washing that forces water deep into the wood grain.

Rotate Inventory Regularly

Storing pallets in one place for extended periods encourages condensation and hidden mould growth. Rotating pallet stock ensures even air exposure and reduces the likelihood of moisture pockets forming within older stacks. This simple practice also helps maintain and extend pallet lifespan.

Apply Protective Coatings or Use Desiccants

Humid or coastal environments demand extra protection. A light mould-resistant coating helps seal the timber, while desiccant packs or silica gel absorb excess moisture in storage areas. These small steps make a measurable difference during long-term or export storage.

What to Do if You Find Mould on Wooden Pallets?

Even with solid preventive measures, mould can still appear after heavy rain or unexpected exposure to moisture. Acting quickly limits the spread and keeps contamination contained.

• Isolate Affected Pallets: Immediately separate any mouldy pallets from clean stock to prevent cross-contamination. Place them in a well-ventilated area for inspection and cleaning.
• Clean and Disinfect: For light mould, scrub the surface with a mild vinegar or diluted bleach solution, then rinse with clean water. Let the pallet dry completely in sunlight or a dry, controlled space. Avoid over-wetting, as excess water can penetrate deeper into the timber and encourage further mould. (For industrial or food-contact use, confirm that cleaning methods meet site hygiene standards.)
• Inspect the Surrounding Area: Check nearby pallets, walls, and floors for dampness, leaks, or condensation. Mould on multiple pallets often indicates an environmental issue, such as poor drainage or insufficient ventilation.
• Decommission Heavily Affected Pallets: If mould has penetrated deep into the wood or produces strong odours, do not reuse those pallets, especially in food, pharmaceutical, or export operations. Decommission and recycle them through authorised timber recovery, mulching, or composting channels in Australia.
• Train Staff and Implement Routine Checks: Train warehouse personnel to identify early signs of mould and report them promptly. Implement scheduled inspection intervals, especially after rainfall, humid weather, or major cleaning activities. Consistent oversight prevents minor mould from escalating into large-scale contamination.

Mould on wooden pallets is a silent threat that can ripple through the entire supply chain. Left unchecked, it leads to product losses, compliance failures, and unnecessary downtime. Through early detection, consistent storage discipline, and preventive maintenance, businesses can maintain product integrity and strengthen operational reliability.

Proactive pallet management is not just about extending pallet lifespan; it’s about ensuring every shipment, delivery, and handling process runs smoothly, safely, and in compliance with hygiene standards.

For reliable heat-treated wooden pallets designed to resist moisture and meet ISPM-15 export standards, contact Waterstone Pallets. We supply durable pallet solutions to help your business maintain safety, compliance, and long-term efficiency across Australia.

FAQs

How quickly can mould develop on wooden pallets?

Mould can begin to grow on pallets within 24 to 48 hours of exposure to high humidity or moisture. Growth accelerates in warm, poorly ventilated spaces, which is why prompt drying and airflow management are essential after rain, washing, or spill incidents.

Can heat treatment completely prevent mould growth?

Heat treatment greatly reduces the likelihood of mould formation by removing most internal moisture, but it does not make pallets permanently immune to mould. If heat-treated pallets are later stored in damp environments, they can still absorb moisture and develop mould over time.

Are there standards or regulations for mould prevention in export pallets?

Yes. Export pallets must comply with ISPM-15 standards, which require heat treatment to kill pests and reduce moisture content. While ISPM-15 does not directly regulate mould, compliance helps minimise the risk.

What should I do with pallets that are beyond cleaning or repair due to mould?

Severely contaminated pallets should be decommissioned and recycled responsibly. In Australia, most recycling facilities convert damaged timber into mulch, composite wood products, or fuel material, keeping waste out of landfills and supporting sustainability goals.

How can warehouses reduce mould risk long-term?

Long-term prevention relies on environmental control and regular monitoring. Maintain consistent ventilation and humidity levels, inspect for leaks or condensation, and implement a pallet rotation schedule to avoid long-term stacking. Periodic inspections, combined with staff training on mould prevention, can greatly reduce the risk of recurring mould on wooden pallets.