Some experiences with attack of microorganisms on wooden constructions supporting foundations of houses and bridges
Reconstructions of bridges and public buildings or damage of houses during the construction of subway lines in Berlin have led to a number of inspections of wooden foundations, mostly pine or spruce piles, representing service lives of between ca. 70 and 140 years. In all cases bacterial attack was found both in wood submerged in ground water and in surface water. The extent of deterioration differs considerably in round wood and sawn wood and, furthermore, depends on the type of soil or water surrounding the wood. Within 140 years sawn scots pine sapwood can be completely destroyed by bacteria occurring below the level of the water table, whereas scots pine heartwood is remarkably durable. On sawn wood, only a small outer surface layer of the heartwood is damaged. In scots pine piles which had been installed about 110 years ago under the Reichstag building in Berlin bacterial attack produced bending strength losses of up to nearly 50% and crushing strength losses parallel to the grain of up to 55% in the outer sapwood as compared to the heartwood.