Microbiological decay of building materials - a comparison between different methods for analysis In this study the decay of seven building materials has been analysed by five different microbiological laboratories after exposure both in laboratory conditions and in crawlspaces in the field. The results from the laboratory exposures showed microbiological growth to at least some extent on all materials. When the laboratories tried to classify the risk of microbiological decay on the seven materials, four of the five laboratories made the same judgement. One laboratory found more severe decay on mineral wool than the others and regarded mineral wool materials as being the most risky. After two years of exposure in crawlspaces in Borås and Umeå microbiological decay has been found on all materials. The decay is most severe on wood and woodbased materials.