I'm a general contractor and I have a problem. I'm going to be working on this house built in 1957 with plaster walls, in the hallway the plaster is peeling and cracking. I though maybe moisture was the problem but they don't use the shower in that bathroom and there is on leak in the exhuast fan. This hallway is in the middle of the house and is the only area in the house that this is happening. Any suggestion.