What is the moldy waterproof exterior wall in Xinbei District of Changzhou?

Is the exterior wall waterproof, which leads to mildew on the wall? The topic is a bit difficult to read.

If the exterior wall is moldy in a large area and is not affected by the weather, it is necessary to check the waterproof problem of the wall. If it does exist, it must be solved, otherwise it will definitely cause the wall to be moldy in the later stage. Although the moldy mildew remover can be removed from the wall, it is also very troublesome if the area is too large.