Moisture content (pallet lumber)
Also called: MC, wood moisture, EMC
Moisture content (MC) is the weight of water in wood expressed as a percentage of the wood's oven-dry weight. Pallet specs usually call for 19% or less when dry wood is needed; green lumber is above about 28%.
In depth: Pallet lumber moisture: green vs kiln-dried, shrinkage, weight and mold
Moisture content drives pallet weight, shrinkage, strength, nail holding and mold. It is measured on a dry basis, so the numbers look high compared with everyday "percent water".
Key thresholds
| MC | Meaning |
|---|---|
| Above about 28% | Above fiber saturation: green, no shrinkage yet |
| 19% | Common "dry" limit (KD19, PDS dry service) |
| 15% | Stricter dry spec (KD15) |
| 12% | Indoor, climate-controlled equilibrium; PDS reports weights at this level |
Why it matters
Below fiber saturation, wood shrinks about 1% of its dimension for each 5% of moisture lost, and it gains strength and stiffness. A PDS example 48 × 40 mixed-hardwood pallet weighed 59 lb (27 kg) green and 37 lb (17 kg) at 12% MC. Above about 19–20%, mold becomes a risk in warm, closed spaces. The Uniform Standard does not set a moisture limit; buyers set one. See pallet lumber moisture.
How it is measured
The reference method is oven-drying samples (ASTM D4442). In practice, receiving docks use hand-held pin or pinless meters, corrected for species and temperature (ASTM D7438 covers field calibration).
On a spec sheet
PDS records MC at manufacture and assembly (for example "Green") and the service environment (dry or wet). An RFQ should state the maximum MC, at what point (manufacture or delivery) and the test method.
Frequently asked questions
How is wood moisture content calculated?
MC = (wet weight − oven-dry weight) ÷ oven-dry weight × 100%. Because it is based on dry weight, green wood can exceed 100%.
What moisture content should pallets be?
For dry service, food, pharmaceutical and containerized export, 19% or less is the common requirement. Some buyers ask for 15% or lower.
What is EMC?
Equilibrium moisture content is the moisture level wood settles at in given air temperature and humidity. PDS uses EMC to describe the service environment: dry is 19% or less, wet is above 19%.
Related
- GuidesPallet lumber moisture: green vs kiln-dried, shrinkage, weight and moldGreen pallet lumber can hold 50–80% moisture; kiln-dried (KD) lumber is dried to about 19% or less. Drier wood is lighter, stiffer and far less prone to mold, but green wood nails more easily and costs less. Heat treatment (HT) for ISPM 15 kills pests; it does not dry the pallet. Specify moisture separately.
- GlossaryWhat does kiln-dried mean for pallets?Kiln-dried (KD) lumber has been dried in a heated kiln to a target moisture content, most often 19% or less (KD19). Kiln drying reduces weight, shrinkage and mold risk, but a KD stamp alone does not show ISPM 15 compliance.
- GlossaryGreen lumber (pallets)Green lumber is freshly sawn wood that has not been dried, with moisture content above the fiber saturation point of about 28%. Many hardwood pallets are built from green lumber because drying adds cost.
- GuidesPallet mold: causes, prevention and what to do with moldy palletsPallet mold grows when wood stays above about 20% moisture in warm, still air: green pallets in containers, wrapped loads or covered yards. The fix is dry wood: specify kiln-dried pallets (19% or less), store them dry and ventilated, and check moisture before loading. HT alone does not prevent mold.
- GuidesHow much does a pallet weigh? Weights by type, material and moistureA standard 48 × 40 wood stringer pallet weighs about 30 to 60 lb (14 to 27 kg). New green hardwood pallets sit at the top of that range and dry ones near the bottom. A EUR pallet weighs about 25 kg (55 lb), pooled 48 × 40 block pallets about 60 to 70 lb, and plastic pallets 14 to 70 lb depending on type.
More in Materials
- GlossaryBark (on pallet lumber)Bark is the outer layer of a tree trunk. ISPM 15 requires wood packaging to be made from debarked wood, allowing only small remnants: pieces under 3 cm wide of any length, or wider pieces with a surface area under 50 cm².
- GlossaryCant (pallet lumber)A cant is a log that has been sawn flat on two or four sides. In the pallet industry it usually means the low-grade center of a hardwood log, left after grade lumber is cut from the outside, which is resawn into pallet parts.
- GlossaryComposite block (pallet)A composite block is a pallet block made from wood chips, particles or fibers bonded with resin under heat and pressure. It does not split like solid wood and, as processed wood, is exempt from ISPM 15 on its own.
- GlossaryCorrugated fiberboard (pallets and slip sheets)Corrugated fiberboard is a board made of a fluted paper medium glued between flat paper liners. It is used for boxes, and in pallet work for corrugated paper pallets, slip sheets, tier sheets and pallet runners.
- GlossaryCut stock (pallet components)Cut stock is lumber already sawn to the finished thickness, width and length of pallet parts, such as 5/8 × 3-1/2 × 40 in deckboards, ready for nailing. It is also called pallet stock or shook.
- GlossaryDouglas-fir (pallet lumber)Douglas-fir is a dense, strong softwood from western North America, also grown in Europe. It is species class 11 (Douglas-fir–larch) in the Uniform Standard and PDS, and class 33 in the European species list.
Last reviewed 2026-09-24. 229 words.