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CLT C24 laminations (EN 16351) - Design Values

CLT C24 laminations (EN 16351) is a cross-laminated timber (clt) grade with reference design values to EN 16351 / EN 338 (C24 laminations). In Eurocode 5 terms its characteristic bending strength fm,k is 24 N/mm², compression parallel fc,0,k is 21 N/mm², and mean modulus E0,mean is 11 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)
24 N/mm²
fc,0,k (compr.)
21 N/mm²
E0,mean
11 kN/mm²

Representative values. Based on C24 laminations (EN 338). Effective panel bending/shear stiffness follows the shear-analogy method for the specific layup - use the manufacturer's ETA or a design engine.

Characteristic values (EN 338 / EN 14080)
fm,kBending strength24 N/mm²
ft,0,kTension parallel14.5 N/mm²
fc,0,kCompression parallel21 N/mm²
fc,90,kCompression perpendicular2.5 N/mm²
fv,kShear strength4 N/mm²
E0,meanMean MOE parallel11 kN/mm²
E0,055th-percentile MOE7.4 kN/mm²
ρkCharacteristic density350 kg/m³
ρmeanMean density420 kg/m³

Source: EN 16351 / EN 338 (C24 laminations). 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 CLT C24 laminations (EN 16351) is described by characteristic values: bending fm,k 24 N/mm², shear fv,k 4 N/mm², compression parallel fc,0,k 21 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 cross-laminated timber (clt) 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 CLT C24 laminations (EN 16351) the mean modulus E0,mean is 11 kN/mm², and the 5th-percentile modulus E0,05 used for stability is 7.4 kN/mm². Characteristic density is rho,k 350 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.

The CLT C24 laminations (EN 16351) figures above are representative of cross-laminated timber rather than of any one manufacturer's product. cross-laminated timber is proprietary: published design values differ between suppliers, and for CLT they also depend on the layup and the panel thickness you actually specify. Use this page for scheme design and take the specific product's evaluation report for the final check.

Common questions

CLT C24 laminations (EN 16351) has a characteristic bending strength fm,k of 24 N/mm² to EN 16351 / EN 338 (C24 laminations). This is a characteristic (5th-percentile) value, not a design strength: divide by the partial factor gamma_M and multiply by k_mod for your service class and load duration before using it in a check.

The mean modulus of elasticity parallel to grain E0,mean is 11 kN/mm², with a 5th-percentile value E0,05 of 7.4 kN/mm² for stability checks. Use E0,mean for deflection under the characteristic combination and E0,05 wherever buckling or lateral-torsional stability is being assessed.

Use the characteristic density rho,k of 350 kg/m³. Fastener capacities in Eurocode 5 - dowel embedment strength, screw withdrawal, nail capacity - are functions of rho,k rather than of the bending or shear strength, which is why two grades with similar fm,k can give different connection resistances. The mean density of 420 kg/m³ is used for self-weight and for serviceability calculations.

Use them for scheme design only. CLT C24 laminations (EN 16351) is an engineered product whose design values are set by each manufacturer's own evaluation report and vary between suppliers and layups, so the figures here are representative of the product class rather than of a specific product. Confirm against the supplier's published data before finalising.

Other Cross-Laminated Timber (CLT) grades

CLT Grade E1 (PRG 320)CLT Grade E2 (PRG 320)CLT Grade V1 (PRG 320)
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