Guaranteed Strength and Superior Straightness
MSR (machine stress rated) Pacific HemFir is rated for highly demanding engineering applications.
MSR Pacific HemFir has been tested and rated for engineered applications where low variability in strength and stiffness properties are a primary product consideration, such as roof trusses, floor or ceiling joists or rafters. MSR Pacific HemFir 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.
The grading system for MSR lumber is based on the established relationship between the stiffness of a piece of lumber and its bending strength. A MSR machine non-destructively tests each piece of MSR lumber to determine its stiffness so that it can be assigned a permitted design stress. Grades of MSR lumber are assigned “f-E” values (e.g. 1950f-1.7E). The “f” value designates the predicted strength in pounds per square inch (psi) and the “E” value designates the average stiffness measured in millions of pounds per square inch (106 psi).
Products like roof trusses will use different grades of MSR lumber within their structure, depending on the particular stresses experienced by the chords composing each roof truss. Most MSR lumber is 2×4; 2×6 and 2×8. MSR lumber is also produced in smaller quantities.
900 Fb-1.0E 1950 Fb-1.7E
1200 Fb-1.2E 2100 Fb-1.8E
1350 Fb-1.3E 2250 Fb-1.9E
1450 Fb-1.3E 2400 Fb-2.0E
1500 Fb-1.4E 2550 Fb-2.1E
1650 Fb-1.5E 2700 Fb-2.2E
1800 Fb-1.6E 2850 Fb-2.3E
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