Johnson County, IA Fire Regulations: Smoke Detectors (2026)

Johnson County's Building Code, adopted under Chapter 8:6 of the Unified Development Ordinance, incorporates the 2021 International Residential Code, including its Section R314 smoke alarm requirements, as part of the Johnson County Building Code effective January 1, 2022. 6(L). Under that exception, interconnecting smoke alarms in an existing area is not required for alterations or repairs that leave the interior wall or ceiling finishes in place and undisturbed, unless an attic, crawl space or basement is already available to route the interconnection wiring without opening up those finishes.

In practice, that means a homeowner replacing a roof, re-siding a house, or making a repair that does not expose the framing is not forced to also rewire and interconnect existing smoke alarms, but a remodel that already opens the walls or ceiling, or a home with an accessible attic or crawl space route, still triggers the interconnection requirement. The Building Official administers this amendment as part of the same permit and inspection process that applies to any other IRC-regulated alteration, and the amendment applies only within the unincorporated areas of Johnson County covered by the UDO.