Guide: mould
Pallet mould in Florida's rainy season
ORLANDO — Pallets grow mould when the wood stays wet, and in Orlando the rainy season makes that the default for anything left in an open yard. Keep wood below 20 percent moisture and it will not support decay fungi.
The rain by month
| Month | Rainfall | What it does to a yard |
|---|---|---|
| June | 8.05 in | The first soak of the season: covers and dunnage go on now |
| July | 7.46 in | Daily afternoon cells; an open stack never dries |
| August | 7.69 in | Mould shows; stock left since May is often cores |
| November | 1.79 in | The dry spell; a damp stack can finally dry out |
What mould needs
Moisture, warmth and still air. Orlando supplies the first two between June and September, so the third is the only one a yard can change. Wood with a moisture content below 20 percent will not support decay fungi, which is the line to manage.
Even slight air velocity, a few feet per second, helps prevent mould on stored pallets. A stack packed tight against a wall, under plastic, with no gap at the ground, does the opposite.
Signs a stack has turned
- Dark, fuzzy or powdery patches on boards, usually near the ends and joints.
- A damp, musty smell when you pull a pallet out of the middle.
- Boards that feel soft or cup when pressed.
- Pallets that are visibly heavier than they should be.
Heat treatment is not a cure
Heat-treated pallets loaded into trailer vans while still hot are susceptible to mould, and heat treatment does not make wood immune. A stamp says what the wood went through, not what it will go through next.
What to do about it
- Keep new stock on dunnage, off the ground, with air through the stack.
- Cover from above but leave the sides open.
- Check the middle of the stack, not just the outside.
- Pull out mouldy pallets; replace the boards or sort them out. Drying alone does not clean a board.
- Dry the rest below 20 percent before it goes to a food or pharmaceutical load.
No guarantees
No stack in an Orlando summer can be promised mould-free. The honest standard is to manage moisture and check, which is why food, pharmaceutical and plant loads always ask how the pallets were stored.
Questions, answered
How do I keep pallets from getting moldy in Florida?
Keep them under 20 percent moisture: off the ground, covered from the top, with open sides and moving air.
Is mould dangerous?
It is a reason to keep pallets away from food and pharmaceutical freight. Treat any stack with visible mould as unfit for those loads until the boards are replaced.
Three summer months carry nearly half the year's rain
June, July and August add up to 23.2 inches on the monthly normals in the table, which is about 45 percent of the 51.45-inch annual figure. November, at 1.79 inches, carries about 3 percent. A yard therefore has a clear calendar: it needs its drainage, dunnage and cover in place before the first week of June, not after the first soaking.
Why used wood starts with an advantage
The Forest Service survey found used pallets with moisture content typically between 10 and 12 percent when tested, against 17 to 20 percent for new ones. That leaves room under the 20 percent line, but not much time: a stack that is open to the afternoon storms of July can climb that eight to ten points while it waits for a truck.
Sources
Last reviewed 11 November 2026.