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 Name | Fb (psi) | E (106 psi) | Ft (psi) | Fc (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 Name | Fb (psi) | E (106 psi) | Ft (psi) | Fc (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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