Not all strength classes are listed in EN338. Here are the main characteristic properties of some strength classes that appear in machine settings tables for machine controlled grading in Europe. (The other design properties can be calculated from the equations in EN384). Many of these are not available on the general market, or even in current use in a manufacturing process – but TR26 is a prime example of a commonly traded non-EN338 strength class (at least in the UK market).
Note this previous advice though – in this case, the primary references will be the latest tables of machine settings (known as AGRs or ITTs). These are available most easily from grading machine manufacturers, but can also be obtained through the SG18 group of Notified Bodies. Everything you will find in EN14081-4 is out of date / replaced by AGRs / ITTs.
| Strength class | 5%ile bending strength (N/mm2) | 5%ile tensile strength (N/mm2) | Mean modulus of elasticity (kN/mm2) | 5%ile density (kg/m3) | Comments |
|---|---|---|---|---|---|
| C36T22 | 36.7 | 13 | 390 | ||
| E15 | 36 | 15 | 420 | ||
| NapierDA | 35 | 13 | 460 | A grade for Douglas-fir from UK and IE | |
| E14 | 32 | 14 | 400 | ||
| E13 | 30 | 13 | 380 | ||
| NapierDB | 30 | 12 | 460 | A grade for Douglas-fir from UK and IE | |
| NapierLA | 30 | 13 | 480 | A grade for larch from UK | |
| TR26 | 28.3 | 11 | 370 | A grade for trussed rafters in the UK | |
| NapierLB | 28 | 12 | 440 | A grade for larch from UK | |
| C25T15 | 25 | 11.5 | 360 | ||
| E12.5 | 25 | 12.5 | 370 | ||
| NapierSA | 25 | 11 | 375 | A grade for spruce from UK and IE | |
| E12 | 24 | 12 | 370 | ||
| NapierSB | 22 | 10 | 360 | A grade for spruce from UK and IE | |
| NapierLC | 21 | 9 | 400 | A grade for larch from UK | |
| NapierLD | 20 | 8 | 390 | A grade for larch from UK | |
| C16+ | 18.5 | 8 | 330 | A grade for spruce from UK and IE | |
| E8.5 | 18 | 8.5 | 320 | ||
| NapierDC | 16 | 10 | 400 | A grade for Douglas-fir from UK and IE | |
| NapierSC | 16 | 8 | 320 | A grade for spruce from UK and IE | |
| NapierSD | 15 | 7 | 310 | A grade for spruce from UK and IE | |
| batten14 | 14 | 7.5 | 330 | A grade for spruce tiling battens from UK and IE | |
| NapierDD | 14 | 9 | 400 | A grade for Douglas-fir from UK and IE | |
| batten12 | 12 | 7.5 | 330 | A grade for spruce tiling battens from UK and IE | |
| batten10 | 10 | 7 | 330 | A grade for spruce tiling battens from UK and IE | |
| L40 | 26 | 14 | 420 | ||
| LD26 | 26 | 14 | 410 | ||
| L36 | 22 | 13 | 400 | ||
| LD22 | 22 | 13 | 390 | ||
| L30 | 18 | 12 | 380 | ||
| LD18 | 18 | 12 | 370 | ||
| L27 | 16 | 11.5 | 370 | ||
| L25 | 14.5 | 11 | 350 | ||
| LD15 | 14.5 | 11 | 350 | ||
| L22 | 13 | 10 | 340 | ||
| L17 | 11 | 9 | 320 | ||
| LD11 | 11 | 9 | 320 |
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