The brick house had been standing for six years without finishing, there were no problems with the walls getting wet. Last year the repairs were made, and the wallpaper was glued. The repair went on for six months, and during that time, too, nothing got wet. This year, in January, the house began to live, two bathrooms were used. Soon I began to notice fungus on the wallpaper, and only on the interior walls, at floor level and up to half a meter in height. The wallpaper began to peel off a little. On the outside walls, where the radiators are, everything was clean. The other day I found wetting and efflorescence on the facing bricks, only in the lower rows, so far only on two walls. Decorative stone, which is used for facing the foundation, is swollen, it is kind of cracked.
What could be the problem? There is ventilation in the bathrooms, the exhaust fans work.