King County, WA Fire Regulations: Smoke Detectors (2026)
Key Facts
- Every Sleep Room
- Required
- New Construction
- Hardwired + interconnected
- CO Alarms
- Required RCW 19.27.530
- 10-year Battery
- Allowed existing homes
- Code
- RCW 19.27 IRC R314
Summary
Smoke alarms required in all King County dwellings per WA Building Code (RCW 19.27, IRC R314). New construction needs hardwired interconnected alarms with battery backup; battery-only allowed in existing homes.
RCW 19.27.530 Carbon monoxide alarms — Requirements — Exemptions — Adoption of rules.
(1) By July 1, 2010, the building code council shall adopt rules requiring that all buildings classified as residential occupancies, as defined in the state building code in chapter 51-54 WAC, but excluding owner-occupied single-family residences legally occupied before July 26, 2009, be equipped with carbon monoxide alarms. (2)(a) The building code council may phase in the carbon monoxide alarm requirements on a schedule that it determines reasonable, provided that the rules require that by January 1, 2011, all newly constructed buildings classified as residential occupancies will be equipped with carbon monoxide alarms, and all other buildings classified as residential occupancies will be equipped with carbon monoxide alarms by January 1, 2013.
(b) Owner-occupied single-family residences legally occupied before July 26, 2009, are exempt from the requirements of this subsection (2). However, for any owner-occupied single-family residence that is sold on or after July 26, 2009, the seller must equip the residence with carbon monoxide alarms in accordance with the requirements of the state building code before the buyer or any other person may legally occupy the residence following such sale.
(3) The building code council may exempt categories of buildings classified as residential occupancies if it determines that requiring carbon monoxide alarms are unnecessary to protect the health and welfare of the occupants.
(4) The rules adopted by the building code council under this section must (a) consider applicable nationally accepted standards and (b) require that the maintenance of a carbon monoxide alarm in a building where a tenancy exists, including the replacement of batteries, is the responsibility of the tenant, who shall maintain the alarm as specified by the manufacturer.
Full Breakdown
Washington State adopts the International Residential Code with amendments; RCW 19.27 establishes the statewide building code enforced locally. IRC Section R314 as amended requires smoke alarms in every sleeping room, outside each sleeping area within 10 feet of bedroom doors, and on every story including basements. New construction after 2010 requires hardwired 120V alarms with battery backup, interconnected so all sound when any detect smoke. Existing homes being sold or substantially altered must be upgraded to meet current code at the time of permit. Battery-only alarms remain legal in existing homes not undergoing remodel. Carbon monoxide alarms are required under RCW 19.27.530 in all dwellings with fuel-burning appliances or attached garages since 2013. King County Fire Marshal (206-296-6600) enforces fire code in unincorporated areas. Rental properties must certify working smoke and CO alarms at tenant turnover per RCW 59.18.060. 10-year sealed-battery alarms satisfy requirements in existing homes under the 2018 state amendment.
Violations & Fines
Misdemeanor under RCW 19.27.097 for building code violations, fine up to 1,000 dollars. Landlord failure to provide working alarms can result in tenant remedies under RCW 59.18 including rent abatement.
Frequently Asked Questions
Can I use battery-only smoke alarms in my older home?
Do I need a carbon monoxide alarm?
Sources & Official References
Other rules in King County
Compare King County to another location·View the Washington fire regulations overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.