Moisture and Bio-Deterioration Risk of Building Materials and Structures

During the service life of buildings, natural aging and eventual damage of materials due to different chemical, physical, and biological processes can take place. Ageing of the materials is one aspect of the environmental processes and involve different chemical, mechanical and biological reactions of the materials. Bio-deterioration, e.g. mould, decay and insect damage in buildings, is caused when moisture exceeds the tolerance of structures which may be a critical factor for durability and usage of different building materials. Modelling of the development of mould growth and decay development is a tool for evaluate the eventual risk of ambient humidity or moisture conditions of materials for biodeterioration of materials. The modelling can be used in combination of hygro-thermal analyses of building and building components. Moisture availability is the primary factor controlling mould growth and decay development, but the characteristics of the substrate and environmental conditions determine the dynamics of the growth. However, moist materials may also dry and become wet again thus, resulting in fluctuating moisture conditions. Mould and decay problems in buildings are most often caused by moisture damage: water leakage, convection of damp air and moisture condensation, rising damp from the ground and moisture accumulation in the structure. Repeated or prolonged moisture penetration into the structure is needed for damage to develop.