C30 (EN 338) - Design Values
C30 (EN 338) is a dimensional lumber grade with reference design values to EN 338:2016. In Eurocode 5 terms its characteristic bending strength fm,k is 30 N/mm², compression parallel fc,0,k is 24 N/mm², and mean modulus E0,mean is 12 kN/mm² (EN 338 / EN 14080). Values are shown before adjustment factors; apply the relevant NDS C-factors or EC5 k_mod and γ_M for your load case.
| fm,k | Bending strength | 30 N/mm² |
| ft,0,k | Tension parallel | 19 N/mm² |
| ft,90,k | Tension perpendicular | 0.4 N/mm² |
| fc,0,k | Compression parallel | 24 N/mm² |
| fc,90,k | Compression perpendicular | 2.7 N/mm² |
| fv,k | Shear strength | 4 N/mm² |
| E0,mean | Mean MOE parallel | 12 kN/mm² |
| E0,05 | 5th-percentile MOE | 8 kN/mm² |
| Gmean | Mean shear modulus | 0.75 kN/mm² |
| ρk | Characteristic density | 380 kg/m³ |
| ρmean | Mean density | 460 kg/m³ |
Source: EN 338:2016. Reference values are shown before adjustment factors (NDS C-factors / EC5 k_mod, γ_M) - apply these per your load case in design.
Understanding these values
Under Eurocode 5 C30 (EN 338) is described by characteristic values: bending fm,k 30 N/mm², shear fv,k 4 N/mm², compression parallel fc,0,k 24 N/mm² and perpendicular fc,90,k 2.7 N/mm². These are 5th-percentile figures, not allowable stresses - divide by the partial factor gamma_M (1.3 for solid timber for dimensional lumber under the recommended values) and multiply by k_mod for the service class and load duration, so the usable strength is materially lower than the number shown.
For C30 (EN 338) the mean modulus E0,mean is 12 kN/mm², and the 5th-percentile modulus E0,05 used for stability is 8 kN/mm². Characteristic density is rho,k 380 kg/m³ with a mean of 460 kg/m³, which is the value that drives fastener and connection capacity rather than any of the strength figures - two grades of similar bending strength can give quite different screw and dowel resistances if their densities differ.
Within the dimensional lumber entries in this catalogue, C30 (EN 338) is the strongest in bending at 30 N/mm², against 16 N/mm² for C16 (EN 338) at the other end of the range.
The closest alternative in the same family is C24 (EN 338) at 24 N/mm² in bending, 25% below this grade. If availability drives the choice rather than capacity, that is the substitution to price first - but re-run the deflection check as well, because stiffness and strength do not always move together.