It shall be unlawful for any person to permit any premises, improved or unimproved, and all open lots and alleys in the city, to accumulate lumber, boxes, barrels, bricks or stones and similar materials that may be permitted to remain thereon and that may be used as a harborage by rats, unless same shall be placed on open racks and elevated not less than 18 inches above the ground, with a clear intervening space underneath, to prevent the harborage of rats. (Ord. 7847)