MSR Lumber Producers Council
Today I am a MSR Lumber Producers Council presenter in Charlotte, North Carolina. Lumber grades take into account natural characteristics, including knots, splits, checks, shake, and wane. Lumber design values are assigned to lumber grades to provide a means for using this material in structural applications. These values are published in Design Values for Wood Construction, a supplement to National Design Specification® (NDS) for Wood Construction. These six design values are bending (Fb), shear parallel to grain (Fv), compression perpendicular to grain (Fc⊥), compression parallel to grain (Fc), tension parallel to grain (Ft), and modulus of elasticity (E and Emin).
Because machine graded lumber has strength properties assessed during production, Machine Evaluated Lumber (MEL) and Machine Stress Rated Lumber (MSR) grading automatically adjusts to changes in internal quality of lumber. Changes to visual grades have no impact on design values of MSR and MEL because of how these products are manufactured and tested.
Produced for six decades, MSR lumber has documented and tested structural design values. In contrast to visual grades, machine graded lumber is produced by measuring physical properties of each piece of lumber in production lines. Manufacturers are required to test samples during each shift and this entire quality assurance process is audited by independent third parties to confirm conformance with published design values. MSR and MEL lumber consistently meet design value requirements even as timber growing practices and environmental conditions change.
Sadly, we’ve had this technology available to reliably test lumber for strength, independent of human eye variability (visual grading) for well over half a century – and we do not universally use it. Visit any local lumber yard, and ask if they have MSR lumber for sale. Chances are your answer will be a resounding “no”. Pick up a “visually graded’ 2×6 at a lumberyard, and you have no idea how strong it really is. Did this lumber grader have a bad day? Was he or she really paying attention on when they were grading lumber? Does it have a huge defect hidden from naked eyes? Can you depend on it to perform how it you think it should?
Engineers and architects are confident in both strength and performance of MSR and MEL lumber. Designers can rely on machine graded lumber properties, use full-design strength, and avoid overbuilding. MSR and MEL lumber have proven to be cost-effective, quality lumber products for component manufacturers and builders. As MSR Lumber Producers Council tag line says, “We Stress Quality”.
Read more about MSR Lumber Producers Council at: http://www.msrlumber.org/
