Iowa Code § 49.23
When a change is made from the usual polling place for the precinct or when the precinct polling place for any primary or general election is different from that used for the precinct at the last preceding primary or general election, notice of such change shall be mailed to all registered voters in the precinct and posted prominently in the county commissioner's office and on the county commissioner's internet site not more than twenty nor less than seven days before the day on which the election is to be held. In addition, a notice of the present polling place for the precinct shall be posted, not later than the hour at which the polls open on the day of the election, on each door to the usual or former polling place in the precinct and shall remain there until the polls have closed.
Iowa Code § 49.23