This report is a publication of the European Network COST E55 "Modelling of the Performance of Timber Structures".

The COST Action E55 (website: www.cost-e55.ethz.ch) entitled "Modelling the Performance of Timber Structures" is a research network established under the aegis of the COST domain "Forests, their Products and Services". The main objective of COST Action E55 is to provide the basic framework and knowledge required for the efficient and sustainable use of timber as a structural and building material. The Action is structured into three working groups, 1) assessment of failures and malfunctions, 2) vulnerability of timber structures and 3) robustness of timber structures.

This report represents the results of work and discussions in working group 1) assessment of failures and malfunctions. This report covers summaries of studies on structural failures on timber structures around Europe and elsewhere. Additionally guidelines on implementing inspections on structures and on the building process concepts to obtain quality and avoid failures are given. These assessment studies and guidelines were drafted by the Cost members (or member institutions).