Various methods have been recommended at different times for preventing damp showing on the inside of a defective wall, one of the most effective being covering the wall with lead foil before papering. At best, this is only a temporary ex-nt, the plaster in time disintegrating, and having to be renewed every two or three years. The best method is to deal with it from the outside. A few coats of wash male as thick as cream with neat Portland cement and applied on the outside will do much to keep out the damp.