BRE DG492 PDF

Timber is an immensely useful but naturally variable material. Wood can contain features, such as knots and sloping grain, that may not be suitable for certain end uses. Dimensional defects and distortion can also affect the use of timber. To use timber reliably for structural purposes, it is important that the strength properties of any member fall within certain limits. Machine grading is a form of non-destructive testing that allows timber to be sorted into strength classes, also enabling timber unsuitable for construction to be rejected. Timber for non-structural uses, such as furniture or flooring, may also be sorted to meet certain appearance grades. This Digest details advances in grading and scanning technology, for both logs and sawn timber, and changes to structural timber grading due to European harmonisation of standards.