timber structure inspection and assessment for conservation.

The diagnosis of timber structures must always be based on a project divided into two distinct analytical levels: the first level consists of a visual inspection performed by technicians using simple instruments to identify the wood species, the thermohygrometric conditions and the natural or artificial durability; the second level of diagnosis employs appropriate instruments to obtain information that cannot be deduced from the first inspection level.

Instrument-aided diagnosis for full-size timber structures has not yet reached a correct level of procedural organisation and nor have reliable techniques evolved to assess either the state of conservation or the load-bearing capacity. Consequently, only when these techniques are adequately widespread among operators will they contribute to the conservation of many timber structures, rehabilitated and conserved in static terms, by works that fully respect both the original conception and the historical-technological role of the structures, as well as the material with which they are constructed

2.1 Visual inspection (first level diagnosis)

The first level is aimed at a general evaluation of the entire structure without an

accurate analysis of the individual timbers. This level helps orient the second, by

identifying the specific needs and priorities for further inspections. The general

evaluation requires simple tools for investigating the wood and appropriate conditions

for the inspection, i.e., accessibility to the structures, sufficient light and clean

surfaces. Furthermore, the availability of a plan of the structure is essential for

mapping the information and for indentifying classes of priorities for the next step.

2.2 Instrument-aided inspection (second level diagnosis)

The second level is based on the information provided in the first level. It

entails a detailed evaluation of the condition of each timber and the joints within the

structure. It requires the same general conditions and involves a thorough visual

inspection of the timber characteristics and a more sophisticated instrument-aided

analysis: e.g., moisture measurements of the wood, microscopic analysis of fragments

for the identification of the species, micro-drilling analysis, etc. Among these, the use

of a portable micro-drilling instrument (e.g. Resistograph? or DDD200?) is

particularly interesting for assessing the state of conservation of the material. The

joints are subject to a detailed assessment at this level of analysis, especially where

previous restorations introduced other materials, so as to evaluate and monitor the

compatibility with the original wood. The second level of analysis is translated into a

comprehensive and - where possible - quantitative mapping of the conditions (in