This standard provides information on the criteria to be used in the assessment of load-bearing timber structures in heritage buildings. It is intended for all those concerned with the conservation of heritage buildings which contain wooden elements, from the building owners or authorities who are responsible for them to the specialists employed. It should also help decision-making regarding the need for immediate measures. Its aim is to guarantee that condition survey and assessment provide the necessary data for historical analysis, structural safety assessment and planning of intervention works. The guidelines can be also applied to any kind of timber member, except the structural members made of engineered panels, such as glued laminated timbers. This standard applies to roof structures and to heavy timber frames with non-structural infilling. It excludes both light stud structures, which often rely upon a boarded cladding for lateral stability, and log buildings.