Mountain View, CA Building Safety: Fire Sprinkler Requirements (2026)

2 to mandate automatic fire sprinklers for new construction citywide. Sec. 15 states plainly that 'an automatic fire sprinkler system shall be installed in one- and two-family dwellings,' with no size threshold for new construction. The section carves out several exceptions for existing housing stock. First, alterations to an existing dwelling that never had sprinklers do not trigger a retrofit on their own. 2, the primary residence lacks sprinklers, the detached ADU is 1,200 square feet or smaller, and it sits on the same lot as the primary home; building an ADU also cannot force sprinklers into an existing, non-sprinklered primary residence.

Third, once an addition to an existing non-sprinklered one- or two-family dwelling equals or exceeds 100 percent of the existing building's square footage, or brings the cumulative building area over 4,100 square feet, a full retrofit sprinkler system becomes mandatory for the whole structure. A parallel rule at Sec. 1, and exempts noncombustible, open-sided parking structures under 5,000 square feet with at least 10 feet of separation from other buildings. The building division of the community development department enforces both sections as part of building permit plan review and final inspection before a certificate of occupancy issues.