GL28c (EN 14080) - Design Values
GL28c (EN 14080) is a glued-laminated timber grade with reference design values to EN 14080:2013. In Eurocode 5 terms its characteristic bending strength fm,k is 28 N/mm², compression parallel fc,0,k is 24 N/mm², and mean modulus E0,mean is 12.5 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 | 28 N/mm² |
| ft,0,k | Tension parallel | 19.5 N/mm² |
| ft,90,k | Tension perpendicular | 0.5 N/mm² |
| fc,0,k | Compression parallel | 24 N/mm² |
| fc,90,k | Compression perpendicular | 2.5 N/mm² |
| fv,k | Shear strength | 3.5 N/mm² |
| E0,mean | Mean MOE parallel | 12.5 kN/mm² |
| E0,05 | 5th-percentile MOE | 10.4 kN/mm² |
| Gmean | Mean shear modulus | 0.65 kN/mm² |
| ρk | Characteristic density | 390 kg/m³ |
| ρmean | Mean density | 420 kg/m³ |
Source: EN 14080:2013. 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 GL28c (EN 14080) is described by characteristic values: bending fm,k 28 N/mm², shear fv,k 3.5 N/mm², compression parallel fc,0,k 24 N/mm² and perpendicular fc,90,k 2.5 N/mm². These are 5th-percentile figures, not allowable stresses - divide by the partial factor gamma_M (1.25 for glued-laminated timber 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 GL28c (EN 14080) the mean modulus E0,mean is 12.5 kN/mm², and the 5th-percentile modulus E0,05 used for stability is 10.4 kN/mm². Characteristic density is rho,k 390 kg/m³ with a mean of 420 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 glued-laminated timber entries in this catalogue, GL28c (EN 14080) ranks 3 of 5 on bending at 28 N/mm²; the strongest listed is GL32h (EN 14080) at 32 N/mm². Grade choice is usually a trade of cost against section depth, so it is worth checking whether a lower grade in a deeper section is cheaper than a higher grade at the depth you started with.