Hardwood lumber is a catch-all term encompassing the processed wood from deciduous or leaf-bearing trees. After the trees are harvested they are cut on a head rig into boards of green lumber. Green lumber refers to the fact this wood still contains a high percentage of moisture. Most species require air drying of the boards prior to drying them in kilns. As a general rule, the denser the species, the longer the air drying process is. Most hardwood lumber bought by end-users is kiln dried to the industry standard of 6% to 8% moisture content. At this point the lumber is stable and less subject to movement.

The National Hardwood Lumber Association or NHLA is the primary authority regarding the grading rules for hardwood lumber in North America. Most species, including imported hardwoods sold in the U.S. are graded using these standards as a guide. The NHLA rules book considers the yield of the lumber as related to defects such as knots, splits, wane, cup, twist, side bend, stain and other issues arising from the processing of the wood and from factors inherent in the wood itself.

The three main grades of lumber are FAS (Firsts and Seconds) / Select and Better, which calls for clear face cuttings (free of defects) of 83 1/3% or better. This is the top grade, but it is important to note that it is not graded as completely clear. This grade is used for where long clear cuttings are required for such things as mouldings, windows and doors.

The next grade down is #1C (1 common). This grade requires a minimum of 66 2/3% – 83% clear face cuttings. It is primarily used by cabinet and furniture manufacturers that require shorter […]