The moisture and microbiological conditions in soil layers under a slab-on-ground structure were examined with extensive field measurements. There had not been any reports of moisture problems related to slab-on-ground structures in the examined case buildings. According to the research, the thermal and moisture conditions under slab-on-ground, warmth and high relative humidity, are favourable to microbe or mold growth. Some kind of microbe growth was therefore discovered in 98% of examined soil samples. The indicator fungus species or actinomycetes-bacteria were discovered in 79% of the samples. According to the results there was no connection between water content or capillarity of the soil samples and the detected microbe growth. Thus, the microbe growth in soil layers under slab-on-ground structures of a heated building is a natural boundary condition in the prevailing thermal and moisture conditions of the fill layers, not an indicator of moisture failure of the ground slab structure.
Building Physics Research Group