This may be a roof leak, a leaking rain water pipe, an overflow that has not been properly fixed, water coming in from the gutters, water coming in from piles of rubbish lying against the wall. The Landlord or Agency will need to investigate and stop the source of the water seepage. Affected areas may need re-plastering or redecoration after a drying out period. Signs of condensation are stains and black powdery mould, especially behind large pieces of furniture, in corners, on colder outside walls, in the kitchen and bathroom, around windows. Clothing and shoes or books in cupboards or wardrobes may become covered in mould.
Condensation is caused when there is excess moisture and cold conditions.
Poor heating, or if you do not use the heating that is there during the winter, will exacerbate condensation. If you dry washing indoors, leave soaking wet towels around, do not open windows when you are at home, boil kettles and pots of water without opening a window to let the steam escape you will probably set off condensation. You can ask the Landlord or Agency to put extractor fans in and this will help if you use them. Let warm air circulate through the house or flat. If you see mould starting up clean it off with a strong cleaning Agent.