the timber network

North American hardwood (NHLA)

  • The standard grades are defined by the National Hardwood Lumber Association (NHLA).
  • Hardwood lumber is usually graded on basis of the size and number of cuttings (pieces) that can be obtained from a board when it is cut.
  • Surface measured is the surface area of a board in square feet. To determine surface measured, multiply the width of the board in inches (") by the length of the board in feet (') and divide the sum by 12 .
Minimum dimensions of the pieces. Clear cuttings Yield Sound sapwood Heart Wane Shakes Knots and holes Deformations
FAS - First And Second Width of 6 " and wider - length of 8 ' and longer 4 " x 5 ' or 3 " x 7 ' 83 1/3 % (10/12ths) to 100% clear-wood cuttings over the entire surface of the board Tolerated without limits Tolerated outside cross cut if the length in inches is smaller than the surface measured. Must not exceed 1/2 of the width of the piece on each edge. Tolerated if the size does not exceed 1/2 of the surface measured The cumulated length must be smaller than 2 times the surface measured. Not considered if not exceeding 1 inch on each extremity. The diameter of each knot or hole must be < 1/3 of the surface measured Tolerated if made straight again during process
FAS One Face - F1F The better face must meet all FAS requirements while the poor face must meet all the requirements of the Number 1 Common grade
SELECTS Width of 4 " and larger - length of 6 ' and longer This grade is virtually the same as F1F except for the minimum board size required
No 1 COMMON Width of 3 " and larger - length of 4 ' and longer 4 " x 2 ' or 3 " x 3 ' from 66 2/3 % ( 8/12ths) up to 83 1/3 % Tolerated without limits < 1/2 of the length Without limits Without limits    
No 2 COMMON Width of 3 " and larger - length of 4 ' and longer 3 " x 2 ' from 50% ( 6/12ths) up to 66 2/3 %. Without limits Without limits Without limits Without limits    
Reference: National Hardwood Lumber Association (NHLA - http://www.natlhardwood.org/)