Using Southern Pine

Grading Methods

Two different grading methods are used to sort Southern Pine dimension lumber and assign appropriate design values: visually graded lumber and mechanically graded lumber.

Visually graded lumber

• Visually graded lumber is the oldest and most common of the two methods. Consistent visual grading is achieved through proper training, education, and supervision of qualified lumber graders. Design values for visually graded dimension lumber are based on results of the North American In-Grade Program that tested full-size pieces of lumber.

  Southern Pine is the only visually graded softwood species that has been regularly monitored. The Southern Pine Inspection Bureau has conducted an annual monitoring program since 1994.

 

Mechanically graded lumber

• Mechanically graded lumber includes both Machine Stress Rated (MSR) lumber and Machine Evaluated Lumber (MEL). Machine grading reduces the variability associated with assigning stress grades to lumber. MSR and MEL are distinguished from visually graded lumber in that each piece is nondestructively tested and then sorted into various strength classifications. Each piece must also meet certain visual requirements before design values can be assigned. Machine grading requires daily quality control tests as well as annual tests. Due to the precise grading process, MSR and MEL provide advantages in more demanding engineered applications, such as long-span trusses.