However, in order to prevent the long-term quality or decoration problems of the top floor of commercial housing, the general decoration master will advise you to do waterproof again when decorating yourself, so as to prevent "the developer's top floor is not waterproof well" from doing it again, which will become "double insurance". It rains in the south, and it doesn't leak after a long time. Therefore, there is nothing wrong with listening to the advice of the decoration master when decorating. They can generally tell whether the top floor of commercial housing is waterproof or not. If they advise you to do it again, there is absolutely nothing wrong with following their advice.