Pasco, WA Accessory Structures: Garage Conversions (2026)

Pasco does not publish a stand-alone garage-conversion ordinance, but its ADU Guide expressly recognizes a 'garage conversion' - whether the garage is attached or detached - as a type of accessory dwelling unit. That means turning garage space into an independent living unit with sleeping, cooking, and sanitation is regulated as creating an ADU under PMC Chapter 25.161 (Ordinance 4575). The maximum size is 1,000 square feet or 55 percent of the main dwelling's total square footage, whichever is less, and the maximum height is 25 feet or the height of the main house, whichever is less. The guide notes that any time a garage or shop is converted or partially used for residential occupancy, the relevant building codes (PMC Title 16) must be met, including fire-separation requirements. Pasco currently allows one attached or one detached ADU per conforming single-family parcel and does not require additional off-street parking, though a converted garage no longer provides covered parking. Occupancy must be long-term (occupants 180+ days per year). Washington's HB 1337 (RCW 36.70A.681) reinforces ADU access statewide by requiring at least 1,000 sq ft be allowed, barring owner-occupancy mandates, and limiting parking requirements near transit; Pasco must align its code by six months after its periodic plan update (Franklin County deadline December 31, 2026). Because conversions involve egress, light, ventilation, and fire-separation code, confirm requirements with the Pasco Permit Center before starting.