Since 1997 the use of wood in bridge construction has been increasingly criticized by the Hamburg federal state authority supposedly because of shortened service life due to decay. With regard to wood research, however, it is often suggested that use of timber is suitable for weathered structures as long as constructive protection measures will be observed. In order to unravel the reasons for the shortened service life in Hamburg, several bridges were examined by visual assessment focussing on decay and especially on design. Thus, details of design which affect the durability of individual bridge components and favour damage propagation as well as subsequent decay were primarily detected. In this respect, faulty planning measures and insufficient wood protection is consequently considered as the main cause of the short service life in Hamburg. Giving examples of pedestrian timber bridges, this practical report illustrates several essential faults of protective design which are still being made in planning and construction of naturally weathered timber structures. However, proven solutions are already available and emphasis is placed on constructive solutions with a positive influence on structure durability.

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