C24
Softwood strength class: bending 24 MPa, E0,mean 11 000 MPa, ρk 350 kg/m³.
The default class for structural softwood in Europe (sawn spruce and fir graded S10 to DIN 4074-1).
All values
- Mechanical 10
- Design values 14
- Physical 2
- Moisture and transport not yet
- Thermal not yet
- Fire 2
- Chemical and durability not yet
Mechanical
Elastic
Modulus of elasticity parallel to grain E0,mean
Mean value, for deformation calculations.
| Condition | Value | Evidence |
|---|---|---|
| 11 000MPa | Confirmed |
Shear modulus Gmean
Mean value, for deformation calculations.
| Condition | Value | Evidence |
|---|---|---|
| 690MPa | Confirmed |
Modulus of elasticity, 5th percentile E0,05
Parallel to grain. Used for stability (buckling, lateral torsional buckling).
| Condition | Value | Evidence |
|---|---|---|
| 7 400MPacharacteristic | Corroborated |
Modulus of elasticity perpendicular to grain E90,mean
Mean value, for deformations across the grain.
| Condition | Value | Evidence |
|---|---|---|
| 370MPa | Confirmed |
Strength
Bending strength fm,k
Characteristic bending strength.
| Condition | Value | Evidence |
|---|---|---|
| 24MPacharacteristic | Confirmed |
Tension parallel to grain ft,0,k
Characteristic tensile strength along the grain.
| Condition | Value | Evidence |
|---|---|---|
| 14.5MPacharacteristic | Corroborated |
Compression parallel to grain fc,0,k
Characteristic compressive strength along the grain.
| Condition | Value | Evidence |
|---|---|---|
| 21MPacharacteristic | Corroborated |
Shear strength fv,k
Characteristic shear strength.
| Condition | Value | Evidence |
|---|---|---|
| 4MPacharacteristic | Corroborated |
Tension perpendicular to grain ft,90,k
Characteristic tensile strength across the grain; small, so details avoid it.
| Condition | Value | Evidence |
|---|---|---|
| 0.4MPacharacteristic | Corroborated |
Compression perpendicular to grain fc,90,k
Characteristic compressive strength across the grain: governs bearing at supports.
| Condition | Value | Evidence |
|---|---|---|
| 2.5MPacharacteristic | Corroborated |
Design values
Modification factor for load duration and moisture kmod
Multiplies characteristic strength: fd = kmod · fk / γM. Wood is weaker under long-lasting loads and when wet.
| Condition | Value | Evidence |
|---|---|---|
| 0.6 | Single source | |
| 0.5 | Single source | |
| 0.7 | Single source | |
| 0.55 | Single source | |
| 0.8 | Single source | |
| 0.65 | Single source | |
| 0.9 | Single source | |
| 0.7 | Single source | |
| 1.1 | Single source | |
| 0.9 | Single source |
Deformation factor (creep) kdef
Final deformation = instantaneous × (1 + ψ2 · kdef) for quasi-permanent loads.
| Condition | Value | Evidence |
|---|---|---|
| 0.6 | Single source | |
| 0.8 | Single source | |
| 2 | Single source |
Partial factor for the material γM
Recommended value; each country may set its own in the National Annex (a Nationally Determined Parameter).
| Condition | Value | Evidence |
|---|---|---|
| 1.3 | Single source |
Physical
Characteristic density ρk
5th-percentile density.
| Condition | Value | Evidence |
|---|---|---|
| 350kg/m³characteristic | Confirmed |
Mean density ρmean
Mean density.
| Condition | Value | Evidence |
|---|---|---|
| 420kg/m³ | Corroborated |
Fire
One-dimensional charring rate β0
Charring depth per minute of standard fire exposure on one face.
| Condition | Value | Evidence |
|---|---|---|
| 0.65mm/min | Single source |
Notional charring rate βn
Includes the effect of corner rounding and fissures; used with the reduced cross-section method.
| Condition | Value | Evidence |
|---|---|---|
| 0.8mm/min | Single source |
Sources here are public pages that reproduce EN 338:2016. For design and acceptance, the standard edition named in your specification and the CE marking and Declaration of Performance of the delivered product take precedence. Design factors are recommended values; your National Annex may set others.