We need to have our terrace functional for the summer which meant tackling the dreaded damp walls. We went with a very simple French drain to take water away from the walls and we also reduced down the amount of soil that was just sitting up against the walls which was one of the biggest reasons the walls were wet. The plan itself is quite simple, a small trench with some clean stone and perforated pipe which should take excess water away from the house and send it somewhere else.