Ohio Rev. Code § 2938.04: Jury demand.

In courts of record right to trial by jury as defined in section 2945.17 of the Revised Code shall be claimed by making demand in writing therefor and filing the same with the clerk of the court not less than three days prior to the date set for trial or on the day following receipt of notice whichever is the later. Failure to claim jury trial as provided in this section is a complete waiver of right thereto. In courts not of record jury trial may not be had, but failure to waive jury in writing where right to jury trial may be asserted shall require the magistrate to certify such case to a court of record as provided in section 2937.08 of the Revised Code.