THE prEN 17121: Historic timber structures - guidelines for the on-site assessment of load-bearing timber structures

The intention of this paper is to present the summary of the prEN 17121, a European standard proposal that will be published within 2019. The scope of the standard is to give guidelines on the criteria to be used for the on-site assess- ment of load-bearing timber structures in heritage buildings. It is intended for all those con- cerned with the conservation of heritage buildings that contain wooden elements, from the building owners or authorities who are responsible for them to the professionals employed. The assessment procedure is based on two phases. The first phase involves: a desk study, a visual survey and a measured survey; the surveys to inform the preliminary structural analysis and the preparation of the preliminary report. The preliminary structural analysis and report should then be used to identify areas of the structure subject to high stresses where a careful inspection is necessary to determine the extent of any damage or deterioration and hence the residual capacity of the members. This is the second phase, which will produce a diagnostic report from the infor- mation obtained by the detailed survey. The detailed survey is aimed at identifying the wood species, at measuring moisture content and moisture gradients, at characterising the biological damage and at assessing the strength of tim- ber. The detailed survey of timber joints closes the survey.