Lumber, Plywood, and Other Wood Products - Carpenter's and Builder's Math, Plans, and Specifications - page 69

use, pieces of lumber of similar mechanical properties can be placed
in a single class called a stress-grade.
Visual grading is the oldest stress-grading method. It is based
on the premise that mechanical properties of lumber differ from
mechanical properties of clear wood because of characteristics that
can be seen and judged by eye. These visual characteristics are used
to sort the lumber into stress grades (see Table 3-2). The following
are major visual sorting criteria:
Density
Decay
Heartwood and sapwood
Slope of grain
Knots
Shake
Checks and splits
Wane
Pitch pockets

Nonstress-Graded Lumber
Traditionally, much of the lumber intended for general building pur-
poses with little or no remanufacture has not been assigned allow-
able properties (stress-graded). This category of lumber has been
referred to as yard lumber . However, the assignment of allowable

Ta ble 3-2 Visual Grades Described in the National

Grading Rule ∗

Lumber Classification Grade Name

Light framing (2 to 4 inches thick, 4 inches wide) † Construction

Standard Utility

Structural light framing (2 to 4 inches thick, 2 to
4 inches wide)

Select structural, 1,
2, 3

Studs (2 to 4 inches thick, 2 to 4 inches wide) Stud

Structural joists and planks (2 to 4 inches thick,
6 inches and wide)

Select structural, 1,
2, 3

Appearance framing (2 to 4 inches thick, 2 to
4 inches wide)

Appearance

∗ Sizes shown are nominal.
† Widths narrower than 4 inches may have different strength ratio.