Lumber types and grades provide information meant to identify the quality of a piece of lumber. Specific rules have been established in regards to hardwoods and softwoods and how they are graded. The most prominent are provided by the National Hardwoods Lumber Association or NHLA.
The post-Civil War era saw huge expansion in this country, with the railroads heading west. The railroads needed quality timber for the ties that hold the long steel tracks in place. A consistent method for measuring and grading needed to be established. These was some of the first grading rules that are now common to all lumber sold in the United States.
Grading rules designate just how many knots and checks are allowed in a given number of running feet. A knot is where a limb has grown from the tree. Checks can occur when the board is allowed to dry to quickly. Other specifics of the grading rules designate the finished thickness and width of the board.
According to the rules, there are two basic types of wood: softwood and hardwood. Hardwoods are classified as trees that lose their leaves every year; softwoods are conifers or evergreens. There are some exceptions, such as Eastern Red Cedar, which has it own sets of rules for grading. Red Cedar is commonly used as a lining for closets due to its natural oil that repels insects.
Grading symbols are stamped onto individual pieces of lumber.
Clear Face Cutting: the best of the best, all clear boards on both sides FAS: clear but may contain some very small splits FAS ONE FACE (FIF): same as FAS but only on one side Selects or No.1 Common: a 75% clear face on one side No. 2 Common: 66.3 % clear face on one side No. 3 Common: 33.3% clear face on one side Below Grade or Sound Cuttings: greater than 80% of the board has defects, checks, splits, knots Sound Wormy: full of small wood worm holes but still a solid piece of wood
When purchasing any type of lumber, be sure to find the grade mark. If a piece of lumber does not have a grade stamp, ask the salesperson for the lot's grading paper. Each lot of lumber is traced from cutting to the drying kiln and identify with grading papers when shipped. If the lumber is not stamped, you may be purchasing inferior lumber that has not been properly graded.