Sun Prairie Fire Regulations: Smoke Detectors Rules (2026)

Wisconsin preempts smoke alarm rules through Wis. Stat. §101.645 (one- and two-family dwellings) and §101.145 (multifamily and other residential buildings such as apartment houses, rooming houses, hotels, dormitories, and tourist rooming houses). Owners must install functional smoke detectors in the basement and on each floor level except the attic, garage, or storage area of each dwelling unit. For multifamily and rooming houses, detectors are also required at the head of any stairway on each floor and either inside each sleeping area or within 6 feet of each sleeping area (not in a kitchen). For new one- and two-family construction, Wis. Admin. Code SPS 321.09 requires smoke alarms inside each sleeping room, outside the sleeping rooms within 21 feet of the centerline of the door opening, and in a common area on each floor level without sleeping rooms; new-construction alarms must be continuously powered by the house electrical service and interconnected so that activation of one triggers all (wireless interconnect is permitted). Occupants are responsible for routine maintenance, but if an occupant or inspector gives the owner written notice that a detector is not functional, the owner has 5 days to repair it. Dane County does not layer additional smoke-detector requirements on top of state law for unincorporated areas; town building inspectors enforce SPS 321 through the Wisconsin Uniform Dwelling Code program. Wisconsin appellate decisions have held that violation of §101.645 is negligence per se in fire-loss litigation.