The city manager shall cause to be posted at each entrance to such building a notice to read: “DO NOT ENTER. UNSAFE TO OCCUPY. City of Ida Grove.” Such notice shall remain posted until the required repairs, demolition, or removal are completed. Such notice shall not be removed without written permission of the city manager and no person shall enter the building except for the purpose of making the required repairs or of demolishing the building. [Code 1975 § 2.3-1.05.]