ProWood pressure treated lumber with grade ink stamp

Grades of Dimensional Lumber & Decking

Different projects require different types of pressure-treated lumber. Lumber mills ink-stamp each board with a lumber grade. Grades refer to the quality, strength and appearance of the wood.

#1 Grade Lumber

Use when both strength & appearance are important.

Characteristics
  • Boards contain small and few knots
  • Knots may be no larger than 2 ¾"
  • One hole is permitted every 3 feet
  • No splits larger than the width of the board
  • Stronger than #2 grade because it has fewer and smaller knots

#2 Grade Lumber

Use when appearance is not important.

Characteristics
  • Grain slope must meet a minimum 1/8-grain slope (the less deviation from straight grain parallel to the edge, the stronger the piece of lumber).
  • Boards contain splits no larger than 1.5 times width of board
  • Knots may not be larger than 3 1/2"
  • One hole is permitted every 2 feet
  • May have wane (bark edge) on corners
  • More knots and bark edges than #1 grade

Prime Grade Lumber

Use when appearance is important.

Characteristics
  • Prime grade lumber provides the same structural properties as #1 grade lumber, but has fewer knots and better appearance
  • #2 Prime grade has the strength of #2 grade lumber, but will look better, with fewer knots

Radius Edge Decking

5/4" wood decking is graded for both strength and appearance and is available in Premium and Standard grades.

Premium Grade

Use when small knots are desired and appearance is very important.

Characteristics
  • Best appearance (compared to Standard)
  • High-quality lumber
  • Smaller and fewer knots

Standard Grade

Use when a rustic appearance is desired.

Characteristics
  • More knots than Premium grade
  • Knots may be larger
Key points
  • Treated wood is typically still wet when it’s delivered to the lumberyard or job site. As it dries, you should expect slight changes in width and length.
  • As lumber dries, it may split, cup and warp. This is more likely to occur to occur in lower-grade boards, where knots and uneven grains are already present.
  • Most lumber and building materials dealers stock only a few grades of lumber but usually allow customers to special-order non-stocked grades of lumber.