Applies to visually graded softwood (F11 stress grading) and hardwood (F11 and F17 stress grades) planks and to mechanically stress graded softwood and hardwood planks. The strength basis is that of a 225 x 38 mm plank for F11 material and a 225 x 32 mm plank for F17 material. A section on proof testing for structural adequacy is included, and an appendix lists suitable species, with an indication of their strength group, moisture content and Lyctus susceptibility.