lumber. Table 3-5 lists the subdivisions for each grade in descending order of quality.
Grades of hardwood lumber are established by the National Hardwood Lumber Association. FAS (firsts and seconds) is the best grade. It specifies that pieces be no less than 6-inches wide by 8-feet long and yield at least 83 1/3 percent clear cuttings. The next lower grade is selects, which permits pieces 4-inches wide by 6-feet long. A still lower grade is No. 1 common. Lumber in this group is expected to yield 6623 percent clear cuttings.
Standard lumber sizes have been established in the United States for uniformity in planning structures and in ordering materials. Lumber is identified by nominal sizes. The nominal size of a piece of lumber is larger than the actual dressed dimensions. Referring to table 3-6, you can determine the common widths and thicknesses of lumber in their nominal and dressed dimensions.
Table 3-5.-Grades and Subdivisions of Lumber
|Grade A||This lumber is practically free of defects and blemishes|
|Grade B||This lumber contains a few minor blemishes|
|Grade C||This lumber contains more numerous and more significant blemishes than grade B. It must be capable of being easily and thoroughly concealed with paint|
|Grade D||This lumber contains more numerous and more significant blemishes than grade C, but it is still capable of presenting a satisfactory appearance when painted|
|No. 1||Sound, tight-knotted stock containing only a few minor defects. Must be suitable for use as watertight lumber|
|No. 2||Contains a limited number of significant defects but no knotholes or other serious defects. Must be suitable for use as grain-tight lumber|
|No. 3||Contains a few defects that are larger and coarser than those in No. 2 common; for example, occasional knotholes|
|No. 4||Low-quality material containing serious defects like knotholes, checks, shakes, and decay|
|No. 5||Capable only of holding together under ordinary handling|