Green lumber
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 green: a GMA-style 48x40 in green mixed hardwood weighs about 59 lb, versus about 37 lb once it dries to 12%.
Also called green wood, unseasoned lumber
Reviewed
On this page
What green means on a pallet spec
PDS records moisture content at manufacture, and "Green" is a common entry for hardwood pallets built from fresh cants. Green wood is heavier, slightly weaker and will shrink as it dries.
| Species | lb per board foot, green | kiln dried |
|---|---|---|
| Mixed hardwood | 4.37 | 2.91 |
| Oak | 5.25 | 3.90 |
| Southern yellow pine | 4.45 | 3.40 |
| SPF | 3.24 | 2.30 |
These are the weight factors palletdesign.ai uses, including nails.
What happens as it dries
- Shrinkage: about 1% of dimension for every 5% drop in moisture content below about 28%. A 5-1/2 in board loses about 1/8 in drying to 19%.
- Strength: stiffness and strength increase as wood dries.
- Nails: smooth-shank nails driven into green wood that then dries lose most of their withdrawal resistance (the Uniform Standard applies a 0.25 factor), which is one reason threaded nails dominate.
- Mold: green pallets in closed containers or humid storage can mold.
When green is acceptable
Domestic, short-cycle use is typical. For containers, some buyers set limits: Costco requires moisture content under 19% for containerized shipments. See moisture content and kiln-dried lumber.
Questions
- Are green pallets bad?
- Not for most domestic uses, but they are heavier, shrink as they dry and can mold in closed containers. Specify kiln-dried when moisture matters.
Related
- Moisture contentMoisture content (MC) is the water in wood as a percent of its oven-dry weight. Dry pallet service means 19% MC or less; green wood is above about 28%.
- Kiln-dried lumberKiln-dried (KD) lumber is dried in a heated kiln to a target moisture content such as 19%. KD is not the same as ISPM 15 heat treatment unless marked KD-HT.
- Pallet lumber moisture contentPallet lumber moisture content drives weight, shrinkage, mold and nail holding. Kiln drying to 19% (KD19) cuts a GMA pallet from about 59 lb to about 39 lb.
- How much does a wood pallet weigh?A standard 48x40 GMA-style wood pallet weighs about 59 lb in green mixed hardwood and about 39 lb kiln dried. How to calculate pallet weight from board feet.
- Heat treatmentHeat treatment (HT) heats pallet wood until its core reaches 56 °C for 30 minutes, the ISPM 15 treatment that lets wood pallets cross borders. Marked HT.
- Helical nailA helical nail has a spiral thread on its shank that turns as it is driven, resisting pull-out. It is the standard pallet nail for medium and dense hardwoods.
Sources
- Guide to Understanding the PDS Specification and Analysis (stringer, inches)
- Uniform Standard for Wood Pallets (NWPCA, now Woodpack Global), 2012 edition
- Costco pallet policy