Mould growth on kiln-dried and air-dried timber

Abstract

The problem with discoloration, due to fungal growth, of wooden outdoor constructions seems to have increased in recent years. One reason for this increase might be an impact of new drying methods of timber. Modern kiln drying methods use high temperatures in an effort to shorten the drying process, which leads to fast capillary water transport and subsequently redistribution and accumulation of dissolved substances at the surface. These can then be used as nutrients by fungi. In this study, wood was dried according to different simulated drying schedules. The mould resistance of the timber was then tested. Wood dried at room temperature was used as a reference. No differences could be confirmed at the end of the test; mould growth was extensive on all the samples. However, mould growth started earlier on the kiln-dried samples than on air-dried timber. As for the discolouring fungus, there was a clear difference between wood dried at room temperature and kiln-dried wood, though no difference could be established between the two artificial methods.