Other Common Grade Marks
Other common grade marks identify the following:
Machine Graded Lumber
Traditionally, lumber has been graded visually. However, machines developed over the past 30 years can quickly test lumber for strength and stiffness. Their levels of predictability are important for roof and floor truss systems and laminated components.
- MSR (Machine Stress Rated or Machine Rated): Typical MSR grades give values for bending strength (Fb) and modulus of elasticity (E), ranging from 1200Fb-1.2E to 3000Fb-2.4E. Facility qualifications and daily quality control must meet the requirements of NLGA Special Product Standard – SPS 2, as approved by CLSAB.
- MEL (Machine Evaluated Lumber): Defined in a slightly different way, MEL grades are identified as M-10 to M-26. Requirements are included in NLGA SPS 2, as approved by CLSAB.
The availability of reliable gluing technology has resulted in a number of new products which take advantage of combining smaller pieces of wood to produce engineered lumber as strong as solid sawn lumber. Requirements for finger joints, edge-glued, face-glued and fingerjoined flange stock are covered by NLGA SPSs or similar product standards, as approved by CLSAB. Two common marks are CERT FGR JNT – SPS 1 (structural fingerjoint) and CERT FGR JNT – SPS 3 (vertical stud use only).