Timber can be graded by visuality and strength. The grading evaluates the properties of all four sides of sawn timber. The most important factors affecting the quality are knots, fissures and deformation.
Quality requirements also include the moisture content and dimensions within tolerances.
Structural timber refers to spruce or pine timber that is used for load-bearing structures or part of such a structure and for which there are set minimum strength and elasticity requirements. Structural timber is graded either visually or by machine.
Machine strength grading is based on mechanical measurements of the timber’s density and knots.
Mainly the same features affect the visual quality and strength but blue stain, discolouring and pitch pockets do not affect the strength of timber.
