Arlington city staff on Monday presented a proposed amendment to the city’s fire code that would require fire sprinkler systems for many additions and accessory dwelling units (ADUs) in single-family and two-family homes. Amy, the staff presenter, told the council the new provision will appear as section 15.24.0.04 in Title 15 and that subsection 7 lists specific exemptions.

Amy said the requirement focuses on sprinklers triggered by additions that convert existing space into an ADU or expand gross floor area, and she noted the code draws on the International Residential Code. “If you add an ADU to your existing single-family, then the existing single-family has to be sprinkled,” Amy said, adding that exceptions apply when an ADU is separated according to IRC §302.3 or when the addition keeps gross floor area under the thresholds listed in the exemptions.

She offered a demonstration video and a cost analysis to help the council weigh the proposal. For a 2,500-square-foot house, Amy said the range of likely installation costs was about $3,007.50 to $7,500, equivalent to roughly $1.50 to $3 per square foot, with variation depending on materials, labor and taxes.

Council members asked for clarification about ADU conversions and how the exemptions operate. Amy confirmed that an ADU created entirely within the footprint of a single-family structure would generally trigger sprinklers for the whole house unless that conversion met one of the enumerated exceptions. She offered to provide the referenced IRC text to the council for review.

The item was presented for direction; no final vote or ordinance adoption occurred at the meeting. Amy said the demonstration video is available for council review and that staff will return for next steps after any requested clarifications.