Lumber intended for general construction is subdivided into stress graded, non-stress graded, and appearance categories. Stress graded and non-stress graded lumber are required to have consistent structural integrity. With appearance lumber, visual quality of the piece is most important and structural integrity is a secondary requirement.

The term "yard lumber" is often applied to the non-stress graded and appearance lumber that is sold by retail lumberyards. With such lumber, grading is done on the better side of a piece after drying and surfacing, and grades are designated by specifying the allowable size and number of defects (e.g., knotholes). This contrasts with hardwoods where most grades are determined from the poorer side of each piece on the basis of a specified number of clear cuttings. Another distinction is that hardwoods are typically graded prior to drying and surfacing.

Non-Stress Graded Lumber

With non-stress graded lumber, pieces are graded primarily for serviceability but appearance is also considered, especially in the higher grades. Imperfections such as knots and knotholes are allowed to become larger and more frequent as the grade drops. The primary product is boards that are less than 2 inches in nominal thickness and 2 inches or more in nominal width. Common nominal widths are 2, 3, 4, 6, 8, 10, and 12 inches. Lengths are usually from 6 to 18 feet in increments of 2 feet. Three to five different Common grades may be applied to boards in this group depending upon the species and the lumber manufacturing association involved. In descending order of quality, the grades are: