I have a corner bedroom. The outer wall is of stucco, the parallel inner one is of wallboard.
One of the interior walls slowly turns a sort of a brownish colour which is taken away by washing the wall with a weak solution of bleach. But after a few months this dirty looking colour returns.
I am wondering what causes the creeping colour to appear on the wall? Could it be mold?
This wall parallels the exterior stucco wall. But I don't detect any cracks that would allow water to seep in, keeping in mind that mold only grows where there is moisture.
This creeping colour change occured during the summer months (no rain) and am curious as to why this is happening being this has never happened previously. Your thoughts?