MSR lumber is evaluated by mechanical stress-rating equipment to measure modulus of elasticity (E), but it also must meet certain visual grade requirements. Unlike visual lumber grades, the evaluated properties become the grade identifier, and are placed on the stamp.
MSR lumber is intended for any engineered application where low variability in strength and stiffness properties is primary product consideration, e.g. trusses, floor or ceiling joists or rafters. Grades are designated by Fb and E. The grade stamp may also include allowable stress parallel-to-grain (Ft), and specific gravity (SG), for horizontal shear (Fv) and compression perpendicular-to-grain (Fc | ) values, when any of these additional properties are specifically qualified through testing and daily quality control. Grades are: