Strength classes you won’t find in EN338

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  Everything you will find in EN14081-4 is out of date / replaced by AGRs / ITTs.

Update 8 May 2023: added some new strength classes and extra information 

Strength class5%ile bending strength (N/mm2)5%ile tensile strength (N/mm2)Mean modulus of elasticity (kN/mm2)5%ile density (kg/m3)Comments
batten10107330A grade for spruce tiling battens from UK and IE
batten12127.5330A grade for spruce tiling battens from UK and IE
batten14147.5330A grade for spruce tiling battens from UK and IE
C16+18.58330A grade for spruce from UK and IE
C25T152511.5360
C36T2236.713390
E122412370Stiffness grade
E12,52512.5370Stiffness grade
E133013380Stiffness grade
E143214400Stiffness grade
E153615420Stiffness grade
E8,5188.5320Stiffness grade
ET242418590For Eucalyptus globulus
ET282819600For Eucalyptus globulus
ET303020610For Eucalyptus globulus
ET343421620For Eucalyptus globulus
ET383822630For Eucalyptus globulus
ET424223640For Eucalyptus globulus
L231310345
L352113400
L362213400
L402614420
L452715440
LD181812370EN1194:1999 Table B.1 (with density)
NapierDA3513460A grade for Douglas-fir from UK and IE
NapierDB3012460A grade for Douglas-fir from UK and IE
NapierDC1610400A grade for Douglas-fir from UK and IE
NapierDD149400A grade for Douglas-fir from UK and IE
NapierLA3013480A grade for larch from UK and IE
NapierLB2812440A grade for larch from UK and IE
NapierLC219400A grade for larch from UK and IE
NapierLD208390A grade for larch from UK and IE
NapierSA2511375A grade for spruce from UK and IE
NapierSB2210360A grade for spruce from UK and IE
NapierSC168320A grade for spruce from UK and IE
NapierSD157310A grade for spruce from UK and IE
TR2628.311370A grade for trussed rafters in the UK
uC12126290A grade for loblolly and slash pine from Uruguay or Brazil

There are also some old tension strength classes with no characteristic density (only “informative values”). These are based on EN1194:1999 Table B.1. Since they are no longer in use, the settings tables with these grades are being withdrawn. These classes are LS11, LS13, LS15, LS18, LS22, LS26. These map on to LD11, LD15, LD18, LD22, LD26 (these is no LD13), which in turn map on to the EN338 T classes (with the exception of LD18, which has slight mismatch of density).

Many old tension strength classes match with EN338 T classes

L16 Match for T10
L17 Match for T11
LD11 Match for T11
LT11 Match for T11
L22 Match for T13
L24 Match for T14
L25 Match for T14,5
LD15 Match for T14,5
LT14 Match for T14,5
L27 Match for T16
L30 Match for T18
LT18 Match for T18
LT21 Match for T21
LD22 Match for T22
LT22 Match for T22
LT24 Match for T24
LD26 Match for T26
LT26 Match for T26

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