Visual grading of timber elements in service

The UNI 11119/2004 standard indicates some classification rules based on the observation of physical or defect characteristics of existing timber structural elements in service, in order to assign the analysed elements to a strength class. The wooden element is inspected from at least three sides, it must be free from opaque coatings (paintings, varnishes, etc.) and some parameters are defined quantitatively, such as: the presence of cracks, the presence of material decay, the presence and dimensions of bevels, single and grouped knots, the inclination of the grain. In order to be assigned to a particular category (I, II or III), all the characteristics and/or defects must fall within the limits specified for each category, or the element must be unclassifiable. Therefore, on the basis of a category assignment, the standard indicates, for timber members of different species, the maximum stresses that can be assumed for the application of the allowable stress method and the average values of the flexural modulus that should be used for the calculation of the deformations of the structure in the serviceability limit states.

Reference standards: UNI 11119:2004; UNI 11035:2022.