Apart from the many problems of dampness caused by actual structural defects or uncommon site circumstances such as an underground stream for example, there is one, which, under certain circumstances, can be common to all buildings.
This form of dampness is condensation, which may be associated with a general surface wetting of an isolated area, and which might be mistaken for external water penetration. It is easy to conclude that there is a leak on a window frame for example, when a morning water puddle on a windowsill is in fact moisture condensed from within the atmosphere of the room. Perhaps the most common form of condensation that we are familiar with is that of steamed up windows, which is experienced during winter conditions when internal temperatures and humidity are high, and external temperatures are low.