Prior to the start of the application of new layers, you need to remove the old layers well, while they are eliminated to a solid foundation. The plaster that has gone from the wall can be determined by tapping, such places usually make a dull sound, this means that this fragment must be repaired. After shrinkage of the house, cracks appear, they are eliminated with a margin, usually about five centimeters, while the crack should narrow to the bottom. It is not easy to apply plaster at the corners, it requires special caution.