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Pallet lumber: species, grades and moisture

Reviewed

In short

Pallet lumber is specified by three things: species class (from Annex B of the Uniform Standard), grade, and moisture content at manufacture. In North America the common choices are mixed Eastern hardwoods, oak, southern yellow pine, SPF and Douglas fir, and weight runs from about 3.2 lb per board foot for green SPF to about 5.3 lb for green oak.

On this page
  1. How pallet lumber is specified
  2. Common species classes
  3. Species compared in palletdesign.ai
  4. Choosing a species
  5. Hardwood vs softwood at a glance
  6. Nails follow the species

How pallet lumber is specified

Pallet parts are usually cut to size from cants or rough lumber, a product the industry calls shook, rather than bought as finished dimension lumber. A pallet spec therefore describes the lumber with three properties rather than a trade size:

  1. Species class: a number from Annex B of the Uniform Standard for Wood Pallets, also used by PDS. A spec can list a mix of up to five class, grade and percent rows.
  2. Grade: the minimum quality, such as Standard &BTR. See lumber grades.
  3. Moisture content at manufacture, such as green or kiln dried to 19%. See moisture content.

Dimensions on the drawing are always actual, not nominal. See nominal vs actual lumber.

Common species classes

Class Group Sort group Examples
1 High-density Eastern hardwoods Medium/high density beech, ash, birch, hickory, hard maple
3 Medium-density Eastern hardwoods Medium/high density soft maple, sweetgum, sycamore, tupelo
7 Low-density Eastern hardwoods Low density aspen, basswood, cottonwood, poplar
21 Eastern oaks Medium/high density red oak, white oak
29 Yellow poplar Low density
11 Douglas fir-larch Medium/high density
12 Hem-fir Low density
13 SPF and similar softwoods Low density spruces, firs, eastern white pine, eastern hemlock
14 Low-density softwoods Low density cedars
22 Southern yellow pine Medium/high density loblolly, longleaf, shortleaf, slash

European and other international species have their own classes (31 to 37, and 41 to 46). The sort group matters for nail choice and for some buyer rules; Home Depot, for example, is documented as excluding classes 7 and 14.

Species compared in palletdesign.ai

palletdesign.ai offers five species. The figures below are the engine's default assumptions, applied to the same GMA-style 48 x 40 stringer pallet (13.5 board feet, 3 notched 1-3/8 x 3-1/2 in stringers).

Species Allowable bending stress (psi) lb per board foot, green / KD19 GMA weight, green / KD19 Lumber price per MBF
Mixed hardwood 1,100 4.37 / 2.91 59 / 39 lb $700
Oak 1,200 5.25 / 3.90 71 / 53 lb $850
Southern yellow pine 1,300 4.45 / 3.40 60 / 46 lb $750
SPF 850 3.24 / 2.30 44 / 31 lb $800
Douglas fir 1,150 3.90 / 3.00 53 / 40 lb $900

How to read this table:

  • Bending stress values are the conservative allowable values palletdesign.ai uses for indicative checks. On the same design, the indicative bending check scales with this value: oak checks about 9% stronger than mixed hardwood, SYP about 18% stronger, Douglas fir about 5% stronger and SPF about 23% weaker. The check catches clearly weak designs; ratings come from a PDS analysis or physical testing.
  • Weights include nails. The mixed hardwood and SPF factors are calibrated against published PDS sheets; the others come from species density tables.
  • Prices are the engine's default assumption for green, standard-grade stock, not market quotes. Kiln drying adds 15% in the estimate.
  • The indicative beam check is a simple, deliberately conservative screen (uniform load, 2 in of bearing on each beam) that catches clearly weak designs. It is not a substitute for a PDS analysis or an ASTM D1185 test.

Choosing a species

  • Weight-sensitive or export loads: lighter softwoods (SPF) or kiln-dried stock cut freight weight.
  • Heavy or racked loads: denser species (oak, SYP, high-density hardwoods) give more bending strength and nail holding.
  • Cost: regional supply matters as much as species. Mixed hardwood is typical in the East, SYP in the South, and SPF and Douglas fir in the North and West.
  • Buyer rules: check retailer guides for banned classes and moisture limits.

Hardwood vs softwood at a glance

Hardwoods (mixed, oak) Softwoods (SYP, SPF, Douglas fir)
Typical form Cut-to-size shook from cants Often dimension lumber (2x4, 1x6)
Typical stringer 1-1/4 or 1-3/8 x 3-1/2 in 1-1/2 x 3-1/2 in
Usual nail Helical Annular for most softwoods
Often supplied Green Kiln dried

Nails follow the species

Helically threaded nails are recommended for medium- and high-density hardwoods. Annularly threaded (ring shank) nails are recommended for low-density hardwoods and most softwoods. See pallet nails.

Questions

What wood is used for pallets?
In North America mostly mixed Eastern hardwoods, oak, southern yellow pine, SPF and Douglas fir. Specs describe them by Uniform Standard species class, grade and moisture content.
What is the strongest common pallet lumber?
Of the five species palletdesign.ai offers, southern yellow pine has the highest allowable bending stress in the engine (1,300 psi), followed by oak (1,200 psi). Actual capacity depends on grade, dimensions and nails.
How much does pallet lumber weigh?
Including nails, about 3.2 lb per board foot for green SPF up to about 5.3 lb for green oak. Kiln drying to 19% cuts that by roughly a quarter to a third.

Sources