Machine Stress Rated lumber (MSR) is evaluated by mechanical stress rating equipment. MSR lumber differs from visually graded lumber in that each piece is nondestructively evaluated and assigned to Bending and Modulus of Elasticity classes. Additionally, each piece must also meet certain visual requirements before it can be labeled.
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 is adequate in most traditional applications, but for more demanding engineered uses, such as commercial/industrial roof and floor systems, glued laminated beams, etc., MSR lumber can often be used instead of steel and concrete.
MSR lumber produced under SPIB's quality control procedures is accepted by regulatory agencies and all major building codes. Two important factors controlling the specification of MSR lumber are bending strength and modulus of elasticity. When ordering grade-marked MSR lumber, specify the bending design (Fb) value and corresponding Modulus of Elasticity (E) value.
Machine Evaluated Lumber (MEL) is similar to MSR in that each piece has been evaluated by non-destructive grading equipment. In addition to meeting certain visual requirements, each piece is sorted into various strength classifications in a MEL production-approved machine. The process also includes daily quality control for bending strength and stiffness, which is required for MSR, plus daily quality control tests for tension strength that are specifically 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 the required design values. The grade names and associated design value combinations are found in the SPIB Grading Rules. Alternately, you can contact individual suppliers for the grades which they produce.
Design Values for MSR-MEL 2014
Contact SPIB today for more information on MSR or MEL.
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