Thurston County, WA Building Safety: Fire Sprinkler Requirements (2026)

2 and adds two Thurston County-specific sprinkler triggers. 3 standards; homes built under the International Residential Code fall outside the IBC's Group R classification. 13 sets square-footage and height triggers for other new, expanded, fire-damaged or substantially improved buildings: inside the Lacey, Olympia or Tumwater urban growth areas, a sprinkler system is required once the completed building exceeds 7,500 square feet and municipal water is available; outside those growth areas, the threshold rises to 12,000 square feet; and any completed building over 35 feet tall needs sprinklers regardless of size, with mezzanine area counted toward the square footage.

A single firewall can split a building in two for this calculation only if neither resulting side exceeds 7,500 square feet. Every sprinkler system required under this chapter must be central station monitored, and where two sprinkler provisions could both apply, the county applies whichever is more stringent. A limited exception exists for enclosed telecommunications equipment spaces carrying their own fire detection system and fire-rated separation. The Community Planning and Economic Development Department enforces these amendments alongside the rest of the adopted International Fire Code.