Honolulu County, HI Fire Regulations: Smoke Detectors (2026)
Key Facts
- Trigger
- Any addition to Group R or I-1
- Alarm type
- Single-station smoke alarms required
- Multiple alarms
- Must be interconnected
- Power source
- Building wiring plus battery backup
Summary
When an addition is made to a Group R or I-1 building on Oahu, the existing structure must get single-station smoke alarms under the county's amended Existing Building Code.
502.6 Smoke alarms in existing portions of a building. Where an addition is made to a building or structure of a Group R or 1-1 occupancy, the existing building shall be provided with smoke alarms in accordance with Section 502.6.1 through 502.6.3 of this code.
(11) Amending Section 502.6. Section 502.6 is amended by adding Sections 502.6.1 through 502.6.3 to read: 502.6.1 Single- and multi-station smoke alarms. Existing Group 1-1 and R occupancies shall be provided with single-station smoke alarms. Exceptions:
1. Where the code that was in effect at the time of construction required smoke alarms and smoke alarms complying with those requirements are already provided.
2. Where smoke alarms have been installed in occupancies and dwellings that were not required to have them at the time of construction, additional smoke alarms shall not be required; provided that the existing smoke alarms comply with requirements that were in effect at the time of installation.
3. Where smoke detectors connected to a fire alarm system have been installed as a substitute for smoke alarms. 502.6.2 Interconnection. Where more than one smoke alarm is required to be installed within an individual dwelling or sleeping unit, the smoke alarms shall be interconnected in such a manner that the activation of one alarm shall activate all of the alarms in the individual unit. Physical interconnection of smoke alarms shall not be required where listed wireless alarms are installed
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-10: Supplement 10, 12-2025 Ordinance No. 25-40 through Ordinance No. 25-56).
Full Breakdown
Honolulu adopted the Hawaii State Existing Building Code, and ROH § 16-9.1 amends its Section 502.6 so that whenever an addition is made to a Group R (residential) or I-1 building, the existing portion of the building must be brought up to smoke-alarm standards, not just the new addition. Section 502.6.1 requires single-station smoke alarms in those existing occupancies, with limited exceptions where alarms already comply with the code in effect when installed. Section 502.6.2 requires interconnection between multiple alarms in a unit, and 502.6.3 sets power-source rules, generally requiring building wiring with battery backup.
Violations & Fines
Completing an addition without upgrading existing Group R or I-1 areas to the required smoke alarms is a code violation enforced by the Department of Planning and Permitting through the building permit and inspection process.
Frequently Asked Questions
Do I need to add smoke alarms to my whole house for an addition?
Can smoke alarms be battery-only in an existing Honolulu home?
Sources & Official References
Other rules in Honolulu County
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