Across Europe is very common to find exterior structures build in sawn and glue-laminated wood. Most of these exterior structures used softwood wood species such as fir, spruce, larch and pine. In Spain wood exterior structures, as for example bridges, became more and more popular since eighties, when sawn and glue-laminated wood were utilized for building exterior wooden structures in overall Spain. This material, sawn and glue-laminated wood, are made in a lot of cases of fir (Abies alba) and spruce (Picea abies), generally from central and northern European production and without a correct treatment to improve their low natural durability because their use is previewed in use classes 1-2 according to the standard EN 335: 2013. The diversity of wood species, preservative treatments and designs, combined with the variability of environmental conditions (different climatic zones and exposure to weathering), has led to the emergence of pathological processes associated primarily with fungal decay (wood destroying fungi) and wood destroying insects in lesser extent. In some exterior wooden structures, the magnitude and extent of the damage due to decay was such that it has reduced the cross section and strength of wooden components, directly affecting the safety of these structures. This paper, with different cases of early decay in exterior structures located in North Spain, tries to summarize the situation of these structures built in the eighties and nineties. In some cases, damages had appeared before ten years of service life. As it will be shown, in this warm and wet area of Spain, wooden parts or joints that create water traps, including the structural elements, present such a destruction level that most of the times the substitution of the bridge is mandatory. So the aims of the study of these cases are to understand the cause of early severe decay. It is important to remark that the definition of a proper approach to degradation of wood exterior structures, different competences such as architects, civil engineers, wood technologists, biologists, etc. are needed. The cases of study have always been analyzed according to the occurrence of decay or failure, but this fact does not mean that all northern Spain exterior structures have this kind of problems, or that are not well designed.

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