Ohio Rev. Code § 731.16
When it becomes necessary in the opinion of the legislative authority of a village, or, in the event a village administrator has been appointed as provided by section 735.271 of the Revised Code, the village administrator, in the prosecution of any work under contract, to make alterations or modifications in such contract, such alterations or modifications shall be made only by the legislative authority by resolution, or, in the event a village administrator has been appointed as provided by section 735.271 of the Revised Code, such alterations or modifications shall be made only by the village administrator in writing, but such resolution or written modification shall be of no effect until the price to be paid for the work and material, or both, under the altered or modified contract, has been agreed upon in writing and signed by the contractor, and by the mayor, or, in the event a village administrator has been appointed as provided by section 735.271 of the Revised Code, the village administrator on behalf of the village. No contractor shall recover anything for work or material because of any alteration or modification, unless such contract is made as provided by this section, nor shall he recover for such work or material, or either, more than the agreed price. The law relating to requiring bids and the awarding of contracts for public buildings, so far as they apply, shall remain in effect. A duplicate copy of each contract shall be filed in the office of the village treasurer.
R.C. §731.16