Nail Sickness occurs with the weakening of  fixing nails to tiles due to the nails which fix them to the battens rusting. A condition of roofing in which the nails fastening roof sheeting rust away to the extent that the sheeting begins to slip over a significant area. Once a roof has become seriously affected by nail sickness the only appropriate method of repair is to strip and resurface the roof. When a roof requires resurfacing, care should be taken to choose a covering with a similar weight to the old roof surface.