Residential Code of Ohio (OAC 4101:8-1-01) Section 105.1: 'Any owner or authorized agent who intends to construct, enlarge, alter, repair, move, or change the occupancy of a residential building or structure, or portion thereof, or to erect, install, enlarge, alter, repair, remove, convert or replace any electrical, gas, mechanical, plumbing system, other residential building service equipment, or piping system the installation of which is regulated by this code, or to cause any such work to be done, shall first make application to the residential building official of a certified residential building department and obtain the required approval.' Section 101.2 applies the code to every one-, two- or three-family dwelling and appurtenances or accessory structures incidental to it.