North American hardwood (NHLA)


  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/)