I have had constant damp in the corner back bedroom of my house (south facing on the first floor). I called a builder around and he noticed the gutters were full of moss. I had gutters cleaned. I turned on the humidifier in the room on the second floor of the property for a week and on the 1st floor for a week until the plaster was dry in both rooms. A week and a half has passed and the wall on the 1st floor is wet again, it is more wet just above the skirting boards than further up the wall and surprisingly in the same place as the original damp areas (the plaster in these areas have remained more darker even after turning on the humidifier and a heater). I have removed the floorboards to check for leaking pipes but there aren't any pipes and the wall under floorboards (below the wet skirting board is completely dry). This is a Victorian Property (1835) with no cavity, has central heating and double glazing. It’s just this corner wall that is wet; the rest of the room is ok. Any assistance would be appreciated.