Softwood is divided into different classes according to DIN 4074-1. The following criteria are assessed according to their occurrence in the piece of wood: tree edges, branches, tree ring widths, fibre inclination, cracks, discolouration, pressure wood, insect damage, curvatures and pith tubes.
Softwood is divided into classes S7, S10 and S13, with the S standing for "visual sorting" and the quality increasing from S7 to S13. The designations MS7, MS10 and MS13 refer to "machine-sorted" wood. The introduction of CE certification, which requires the requirements of the European standard DIN EN 14081-1 for construction timber, requires the classification into strength classes according to EN 338. These are divided into C14, C16, C18, C22, C24, C27, C30, C35 and C40, with C16 roughly corresponding to sorting class S7, C24 to sorting class S10 and C30 to sorting class S13.
The grades of hardwood bear the designation LS according to DIN 4074-5 and the designation D according to EN 338.
Source: bauwion
