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Machine Stress Rated (MSR) and Machine Evaluated (MEL) Lumber

Grading of lumber in North America

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MSR - Machine Stress Rated Lumber

MSR is lumber that has modulus of elasticity E evaluated by mechanical stress equipment, with each piece being marked to indicate the modulus of elasticity E.

Grade NameFb
(106 psi)
1350f-1.3E 1350 1.3 750 1600
1450f-1.3E 1450 1.3 800 1625
1650f-1.5E 1650 1.5 1020 1700
1800f-1.6E 1800 1.6 1175 1750
1950f-1.7E 1950 1.7 1375 1800
2100f-1.8E 2100 1.8 1575 1875
2250f-1.9E 2250 1.9 1750 1925
2400f-2.0E 2400 2.0 1925 1975
2550f-2.1E 2550 2.1 2050 2025
2700f-2.2E 2700 2.2 2150 2100
2850f-2.3E 2850 2.3 2300 2150
  • Fb - allowable 10-year load duration bending stress parallel to grain
  • E - modulus of elasticity
  • Ft - allowable 10-year load duration tensile stress parallel to grain
  • Fc - allowable 10-year load duration compressive stress parallel to grain

MEL - Machine Evaluated Lumber

MEL is lumber where a parameter like density is evaluated nondestructively by mechanical grading equipment to predict certain mechanical properties. A MEL machine evaluates each piece and sorts each piece into various strength classification grade categories.

Grade NameFb
(106 psi)
M-10 1400 1.2 800 1600
M-11 1550 1.5 850 1675
M-14 1800 1.7 1000 1750
M-19 2000 1.6 1300 1825
M-21 2300 1.9 1400 1950
M-23 2400 1.8 1900 1975
M-24 2700 1.9 1800 2100
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