MACHINE STRESS RATED LUMBER
Machine Stress Rated lumber (MSR) is lumber that has been evaluated by mechanical stress rating equipment. MSR lumber is distinguished from visually graded lumber in that each piece is nondestructively evaluated and scored in Modulus of Elasticity classes. Following this "E" assignment, each piece must also meet certain visual requirements before it can be assigned engineering design values.

Under the SPIB Mechanically Graded Lumber Procedures, each producer must meet rigid certification and quality control requirements. MSR lumber must be sampled from production on a daily basis, and tested to over twice the rated bending value. SPIB's quality supervisors monitor each mill's conformance to SPIB procedures for in-plant quality control through regular, unannounced inspections.

Visually graded lumber more than adequately meets the needs in most traditional applications, but for those more demanding engineered uses, such as commercial/industrial roof and floor systems, glued laminated beams, etc., MSR lumber can be advantageous in competing against steel and concrete.

MSR lumber produced under SPIB's quality control procedures is accepted by regulatory agencies and all major building codes. Bending strength and modulus of elasticity are two important factors controlling the specification of MSR lumber. When ordering grade-marked MSR lumber, specify the bending design (Fb) value and corresponding Modulus of Elasticity (E) value.

MACHINE EVALUATED LUMBER
Machine Evaluated Lumber (MEL) is similar to MSR in that each piece has been evaluated by non-destructive grading equipment. A machine approved for MEL production evaluates each piece, sorting the material into various strength classifications. Each piece is also required to meet certain visual requirements. In addition to daily quality control for bending strength and stiffmess which is required for MSR, daily quality control tests for tension strength are required for MEL lumber.

MEL Lumber produced under SPIB's quality control procedures is accepted by regulatory agencies and all major building codes. When ordering grade-marked MEL lumber, specify the grade name corresponding to your required design values. The grade names and associated design value combinations are found in the SPIB Grading Rules, or contact individual suppliers for the grades which they produce.

Contact SPIB today for more information on MSR or MEL.