Proposal for visual grading criteria of structural timber of sweet chestnut from Spain

Bending strength, modulus of elasticity and density were obtained for 981 specimens of Spanish Sweet Chestnut (Castanea sativa Mill.) sawn timber from five provenances. Four-point bending tests were made with three sizes (40 × 100 × 2,500, 40 × 150 × 3,500 and 70 × 150 × 3,500 mm) according to EN 408 (CEN EN 408:2011). Visual grading criteria were established, resulting in 82 % of the samples being classified as one structural quality, namely MEF. Characteristic values of the density and the mechanical properties were determined according to EN 384 (CEN EN 384:2010a): E0,mean = 12.3 kN mm−2; fm,k = 28 N mm−2 and ρk = 510 kg m−3. Therefore, a strength class D24 was assigned according to EN 338 (CEN EN 338:2010b). The relationship between the modulus of elasticity and bending strength was lower (R2 = 0.26) than for Spanish coniferous species.