It is often assumed that dampness within buildings is due in some way to a ‘failure’ of the building. This often will then lead to the incorrect assumption that the building needs to be ‘fixed’ and what often happens next is unnecessary modern remedial damp-proofing.
It is well worth looking at all options for the source of excessive moisture, especially when a floor or wall has become saturated.
Leaking water mains and stop cocks are surprisingly frequent causes of excessive moisture in a building. You will need to locate and fix this problem, then dry the building out (which can take a few months at least) before try to do internal repairs.
Old lead water pipes are especially problematic to this and also a new water main that has been recently installed. Keep a look out for the problem.