A maintenance question for only experienced civil engineers?

Two years ago, I purchased a brand new ground apartment in a building erected on a slopping road. One side of the apartment has a wall that is actually dug in the ground and the ceiling of the apartment is level with road on that side. Only recently, that we have noticed that the paint of the wall started pealing off as a result of, what seems to be, some moisture. I am collecting all ideas and information as how to cope with the problem. Your suggestions are highly appreciated.