No. 3 lumber allows more defects than No. 2 grade and is used for economy pallet construction.
Detailed Definition
No. 3 is a lower visual grade of softwood dimension lumber defined in the grading rules of agencies such as SPIB, WWPA and WCLIB under the American Lumber Standard system overseen by the ALSC. Compared with No. 2 lumber, it allows larger knots and knot holes, more wane, and longer splits and checks, so its published design values are lower. It is often used for pallet parts where loads are moderate and appearance does not matter, but whether a No. 3 board works in a given pallet depends on its size, span and position.
Defects No. 3 allows and why they matter
The extra knots and grain deviation allowed in No. 3 reduce bending strength and stiffness more than they reduce compression strength. In a pallet, that makes No. 3 a more comfortable choice for parts that are well supported, such as deck boards on pallets stored on the floor, than for stringers or boards that must span an open rack. A large knot near the middle of a span, or at a notch in a stringer, is a typical starting point for a break.
Checking a No. 3 delivery
- Look for the grade stamp, or the agreed grade description on the paperwork if the stock is unstamped.
- Check knots at nail lines and at stringer notches, where splitting is most likely.
- Watch for wane on deck board edges that leaves too little wood under the fasteners.
- Confirm moisture condition separately, since the grade does not tell you whether the wood is green or dry.
When to step up to No. 2
If a pallet will be racked, stacked several high or reused many times, the higher design values of No. 2 may let you use thinner boards for the same capacity, or give more margin with the same design. Run both grades through the design, or ask the supplier for rated capacities for each, rather than assuming one is always cheaper.
Authoritative Sources
- American Lumber Standard Committee (ALSC): the committee that accredits lumber grading agencies under the US Department of Commerce voluntary product standard PS 20.
- Pacific Lumber Inspection Bureau (PLIB): the lumber grading agency accredited by the American Lumber Standard Committee for Pacific softwoods used in pallet production.
- Southern Pine Inspection Bureau (SPIB): the lumber grading authority for Southern Yellow Pine, the most common pallet stock in the US Southeast.
Related Glossary Terms
Frequently Asked Questions
Is No. 3 lumber the same as pallet grade lumber?
Not exactly. No. 3 is a defined visual grade under softwood grading rules, with set limits on knots, wane and splits. Pallet grade or pallet stock is a trade description used by mills and pallet makers, and its meaning varies by supplier and region. Some pallet stock is No. 3 or better, and some is ungraded hardwood cants. If the grade matters for your load, ask for a defined grade rather than a trade name.
Will a pallet made from No. 3 lumber meet ISPM 15?
Lumber grade has nothing to do with ISPM 15. The export standard requires solid wood packaging to be debarked, treated by an approved method such as heat treatment to a core temperature of at least 56 C for 30 continuous minutes, and marked by a registered facility. A No. 3 pallet that has been properly treated and marked meets ISPM 15 just as a No. 2 pallet would.