Dampness in exterior wall is mainly due to rains. Too much of dampness on wall will damage the plaster of that wall. And only an experienced or knowledgeable plumber can make out the amount of damage caused to the plaster due to dampness. Indeed dampness on wall means damage is already caused to plaster.
Dampness on wall could be due to various reasons like rain water accumulation, improper plumbing, pipe defect, and crack in wall or porosity. If a home owner notices dampness only during monsoon season then the cause of dampness is rain water. Usually one would think that, damage is caused only where dampness is seen. But as per water capillary action, water can travel to other areas of the wall and cause damage to other areas or other wall too. In monsoon the rain water usually gets accumulated on parapet wall (locally called as “chajja”) which causes dampness.
In case of crack formation too, plumber will not suggest immediate reparation. Plumber will do the needful only if the plaster is affected or damaged due to cracks. Until then is will be left untouched or untreated.
Plaster is only therefore repaired when it is majorly affected or damaged.