Lumber Grades

ProWood Lumber with Black End Tag Side View

CHoosing the right Lumber For your Project

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.

  • Boards contain few, small 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
    Grades of Professional Lumber and Decking

#2 Grade Lumber:   

Use when appearance is not important.

  • 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.

  • 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

Premium Grade:

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

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

Standard Grade:

Use when a rustic appearance is desired.

  • More knots than Premium grade
  • Knots may be larger

Radius Edge Decking

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


  • 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 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.


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