If you found mold in a biulding, do they close down the building?

No, the building is not condemned. It costs far less to remove mold than it does to replace an entire building. As well, the existence of molds such as mildew is not even a reason to close down the building. There are but a few strains of mold which are considered harmful to human health. Mildew isn't one of those molds, and can be cleaned by use of simple bleach and water, with a bit of soap.