In most of the excavated Great Houses, there are some surviving original wood and mud roofs that form the second or third story floors. When backfilling or other treatments are not feasible, a modern shelter roof has been constructed over these fragile elements to protect them from damage and weathering. These shelters are designed to be as unobtrusive as possible by using colors and textures that blend in with the surroundings. Even applying mud plaster to fragile masonry walls is considered a type of shelter coating. This plaster (or the modern roof) is a sacrificial surface that will deteriorate before the original materials are damaged.