65 ILCS 5/11-8-3

For the purpose of guarding against the calamities of fire, the corporate authorities of each municipality may prescribe the limits within which wooden buildings shall not be erected, placed, or repaired, without permission, and, whenever buildings within the fire limits have deteriorated or have been damaged by any means to the extent of 50% of their value, may direct that such buildings shall be torn down or removed, and to prescribe the manner of ascertaining whether the specified damage has occurred.