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Two different grading methods are used to sort Southern Pine dimension lumber and assign appropriate design values: visually graded lumber and machine 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 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 is regularly monitored, ensuring consistent product quality. The Southern Pine Inspection Bureau has conducted an annual In-Grade Resource Monitoring Program since 1994. The results demonstrate how Southern Pine values have remained at a high level, year after year.
Visually graded lumber adequately meets the structural requirements for most typical component applications. For better appearance, specify a higher grade of visually graded lumber, or machine graded lumber.
Machine 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.
Most Southern Pine manufacturers of machine graded lumber already put more restrictive limits on wane than the No.2 visual grade limits required by the SPIB Standard Grading Rules for Southern Pine Lumber. However, one option to guarantee better appearance is to specify that the wane limits meet a No.1 visual grade. Look for the 1W added to the grade mark.
Reinspection Availability
In absence of a special agreement between buyer and seller, the SPIB Standard Grading Rules for Southern Pine Lumber requires that the purchase, sale, or shipment of lumber follow all provisions of the rules, including inspection of any lumber. For complete reinspection information, contact:
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