The use grades defined in standard NF EN 335-2 list the various timber use situations corresponding to a greater or lesser degree of exposure to damaging biological agents. Each species, according to its natural or treatment-obtained durability, may be used in one or more use grades.
The visual grading of the appearance of European softwoods, defined in European standard NF EN 1611-1 and applying to European softwoods, is based on visual criteria concerning the appearance of timber surfaces and edges in relation to the type, amount and location of any unusual feature, cutting imperfection and distortion.
The visual structural grading defined by standard NF B 52-001 distinguishes between 3 options referred to as ST-I, ST-II, ST-III, corresponding to the designations C30, C24 and C18. The letter C (grade) is followed by the number that corresponds to the characteristic flexural strength value expressed in megapascals (Mpa). Grade C18 is suitable for use as traditional sawn timber, grade C24 is used mainly for structural sawn timber products (roof trusses) and grade C30 is recommended for high-performance glued-laminated timber products.