Conservation of historic timber roofs: knowledge, monitoring, strengthening

The lack of knowledge of structural behaviour often led to their substitution with modern structures, or to invasive strengthening operations. If ignorance was the first cause of this loss, knowledge is the first goal to be reached. In unfavourable environmental conditions wood can undergo rapid decay, thus it is necessary a monitoring plan. The theories of preventive conservation underline the need to reaffirm the maintenance practices, and modern technologies could help to lower the cost and increase effectiveness of this operations. In absence of decay processes, historic structures are still suitable to carry out their bearing function. However the need to prevent damage due to exceptional loads, the increase of loads, or the progress of decay could lead to the necessity of strengthening. Strengthening must be viewed as a part of the discipline of restoration, thus it must aim to the conservation of the structure in its material and immaterial features.