Do ADUs need fire sprinklers in my state?
It depends on your state and local codes. Some states require fire sprinklers in new residential units (which include ADUs), while others offer exemptions for ADUs under certain conditions:
California: California’s Residential Code (CRC) Section R313 mandates automatic fire sprinkler systems in all new one- and two-family dwellings. However, a 2017 law (SB-1069) created an exception for ADUs. If the primary residence isn’t sprinklered and the detached ADU is under 1,200 ft², local authorities cannot require a sprinkler system for the ADU. In practice, this means:
New ADUs must have sprinklers if the main house has a sprinkler system (since the main house was required to have one).
If the main house does not have sprinklers, a new ADU ≤ 1,200 ft² on the same lot is generally exempt from adding sprinklers. (This exemption was designed to encourage ADU construction without costly upgrades.)
Large or special-case ADUs might still trigger requirements – for example, many jurisdictions require fire sprinklers if an ADU exceeds 1,200 ft² or is located more than ~150 feet from the street (beyond easy fire truck access). Always check local fire codes: an ADU that is very large or hard to access may need sprinklers even if smaller ADUs don’t.
Colorado: Colorado has no blanket statewide sprinkler mandate for ADUs, but many local jurisdictions require sprinklers in new residential construction. For example, cities like Boulder, Golden, and others in Colorado mandate sprinklers in one- and two-family homes (which would include detached ADUs). If you’re building an ADU in Colorado, consult local codes – in high fire risk zones or certain counties, detached ADUs often must include a NFPA 13D sprinkler system unless an approved alternative is accepted.
Maryland (and others): Maryland and California are currently the only two states with a statewide requirement for fire sprinklers in all new single-family homes. In Maryland, any newly built ADU would need a residential sprinkler system by default. Other states generally do not mandate sprinklers statewide, but major cities or counties might have their own rules. For instance, some communities in Oregon, Washington, Arizona, and elsewhere impose sprinkler requirements for ADUs in certain cases (Scottsdale, AZ has long required sprinklers in all new homes). Always verify your local building and fire code: ADU sprinkler rules can vary widely.
If your state or city requires sprinklers in new dwellings, your ADU will need a fire sprinkler (or a code-compliant alternative like Automist). If sprinklers aren’t required for your main house and your ADU is small and accessible, you likely won’t be forced to add one – though installing a fire suppression system can still greatly improve safety. It’s best to check with your local building department or fire marshal to understand the exact requirements for ADUs in your area.
Disclaimer:
This information is provided as a general reference and should not be considered a complete guide to all applicable building or fire safety regulations. While we strive for accuracy, the content reflects information available at the time of publication and is not a substitute for official code documentation or professional advice. Requirements may vary depending on your local building department, fire marshal, or authority having jurisdiction (AHJ). Always consult your local officials to confirm specific compliance obligations.
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