The numbers shall not be less than two and one-half inches in size and placed conspicuously on each building by the owner.  In case any owner of any building fails to place the number on any building owned by him as required by Sections 911.01 through 911.03, it shall be done by the City and the cost shall be assessed on the lots or lands on which the same is placed, and collected as other assessments.
(1979 Code 93.62)