Lumber impregnated with chemical salts to preserve it against decay is taking the place of steel and concrete as a building material. “Preserved” wood has long been used by railroads for bridge timbers and ties, and now that steel is in demand for war purposes, treated wood is finding far wider uses. It is termite repellent, clean, odorless and easily painted. One preservative, chromated zinc chloride, also gives wood substantial resistance to fire.