Except as otherwise provided, no person shall erect, construct, change the use of, or provide an addition of more that 20% to, any building or structure or any part thereof, or cause the same to be done which fails to support adequate radio coverage for the Minnesota Regional Radio Communications System, including, but not limited to, firefighters and police officers. This section shall not apply to: buildings of less than 8,500 square feet; or any building constructed of wood frame; provided none of the aforementioned buildings make use of any metal construction or any below grade levels or parking areas. Any part of any R-3 occupancy building, including below grade levels and parking areas, are exempt from the requirements of this section. For the purposes of this section, parking structures and stairwells are included in the definition of BUILDING and stair shafts and elevators are included in the definition of ALL PARTS OF THE BUILDING. For purposes of this section, ADEQUATE RADIO COVERAGE shall be an average received field strength of no less than -93 dBm, or 1% BER, measured at 30 to 36 inches above the floor over 90% of the area of each floor and other critical areas determined by the Fire Chief or the Fire Chief’s designee such as fire command centers, stairwells, elevators, high hazard areas, basements, and parking areas. Without an in-building radio system, only the received signal level standard must be achieved as the talk out path is equivalent to the talk in path in this regional radio system.