Wood is a biologically originated material and because of that is characterized by natural decay when exposed and not protected. Decay agents like UV rays and rain makes wood loose its material characteristics and decay. Of course, decay processes affect in some way all the construction materials, but in different forms and with different timing. For wood the main risk is represented by rotting and less frequently by xylophages insects. Rotting takes places only for high moisture content, usually when the relative humidity of the wood element is higher than 20%. Xylophages insects usually don’t attack engineered wood products like glulam, CLT, OSB and plywood.
In general durability of timber constructions can be guaranteed with appropriate precautions and proper maintenance so that the service life of a wooden construction is long as required. To guarantee the necessary durability are fundamental a good design of details and a proper maintenance.
In general, it should be avoided directly to expose wooden structures to the weathering. Roofs should be protected by a package of roofing materials, and vertical columns or walls should be kept insulated from ground moisture with appropriate interface elements. Good detailing can minimize or even eliminate the need of maintenance treatments.