Constructional aspects and the use of school building had led to moisture and mold damages confirmed by microbiological analysis from material, surface and air samples. Cultivation methods were used to assess mesophilic fungi and actinobacteria. High concentrations of microbes (10 5 -10 6 cfu/g in different materials) were recovered from the samples. Microbes included great variety of moisture indicating species (e.g. Aspergillus versicolor, Trichoderma, Fusarium, Stachybotrys, Chaetomium, Streptomyces). The leaking roof of the building was repaired and all damaged materials were removed and replaced by new ones. Spreading of microbial propagules was not effectively prevented. Only part of the wet constructions were dried. After repair the building was cleaned by conventional methods with no special effort focused on removal of fine dust. Sufficiency of cleaning was evaluated by microbiological sampling from material surfaces having abudant and diversiform microflora. Thereafter the building was cleaned using techniques adapted for washing off mold dust. Two weeks after this cleaning, abundance and diversity of microflora had diminished. According this result, all-out cleaning is required to get rid of mold dust arisen during repair of moisture and mold damages in the building. After the building was taken in use, diversity of microflora returned but the concentrations remained low.