Status of machine stress-rating of lumber 25 years after commercial implementation

Machine stress-rating (MSR) of lumber has been in commercial use for 25 years. This grading process has grown very moderately during its initial phase of development. However, since 1980, MSR has experienced a rapid expansion internationally as more emphasis is being placed on the reliability of timber as an engineering material. This paper examines the current status and trends of MSR from the equipment and production standpoints. Literature review, coupled with a survey conducted by the authors in 1988, reveals that MSR is now implemented in all major industrial countries. The number of grading machines installed through 1987 approaches 400, that is, a threefold increase from 1980. MSR production has also tripled over the last 10 years. However, this production remains small, averaging 1.5 percent of total softwood lumber production in North America. Continued growth is expected with advancements in grading equipment technology and an increase in the sophistication of timber building practices.

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