King County, WA Building Safety: Fire Sprinkler Requirements (2026)
Key Facts
- Trigger
- No approved fire apparatus access
- Trigger
- Floor area over 10,000 sq ft
- Trigger
- Fire flow under 1,000 gpm/no hydrant nearby
- Exemption
- Lots 35,000+ sq ft outside Urban Growth Area
- Citation
- K.C.C. § 17.04.560
Summary
Unincorporated King County requires automatic fire sprinklers in new IRC-built homes when fire access, floor area, or water supply fall short of set thresholds, with an exception for large rural lots outside the Urban Growth Area.
An automatic sprinkler system shall be installed in the habitable space of structures built under the International Residential Code (IRC) when:
1. There is no approved fire access as defined in K.C.C. Title 14 and IFC 503;
2. The structure has a total floor area, including basements, that exceed 10,000 square feet; or:
3. There is not: 3.1 A minimum fire flow of 1,000 gallons per minute as defined in IFC Appendix B; or 3.2 A fire hydrant within 400 feet or 600 feet of the property line as outlined in IFC 507.5.1. EXCEPTIONS: Structures are located on lots that:
1. Are sized 35,000 square feet or larger;
2. Are outside the Urban Growth Area; and
3. Have a residential use as the primary land use. (Ord. 19485 § 195, 2022: Ord. 17837 § 84, 2014: Ord. 17837 § 84, 2014: Ord. 15802 § 7, 2007: Ord. 14915 § 83, 2004: Ord. 14111 § 218, 2001: Ord. 12560 § 174, 1996. Formerly K.C.C. 17.04.01027).
Full Breakdown
King County Code § 17.04.560 amends the International Fire Code to mandate sprinklers in habitable space of structures built under the International Residential Code whenever there is no approved fire access, total floor area (including basements) exceeds 10,000 square feet, or the site lacks 1,000 gallons-per-minute fire flow or a hydrant within 400-600 feet. Homes on lots of 35,000+ square feet outside the Urban Growth Area with residential use as the primary land use are exempt. This applies only to unincorporated county land, not Seattle, Bellevue, Kent, Renton, or other incorporated cities, which enforce their own fire codes.
Violations & Fines
The King County Fire Marshal's Office enforces this at building permit and inspection stage under K.C.C. Title 23; a triggering home cannot get a certificate of occupancy without an installed, tested sprinkler system.
Frequently Asked Questions
Does this rule apply inside Seattle?
What size house triggers the sprinkler requirement?
Can a rural lot avoid the sprinkler mandate?
Sources & Official References
Other rules in King County
Compare King County to another location·View the Washington building safety overview
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