Accessory Structures in Kennewick, WA (2026)
5 verified accessory structures rules for Kennewick, Washington, sourced directly from the municipal code and official government pages.
Verified from official government sources
ADU Rules
Kennewick (Benton County, population approximately 84,000) is a Washington city subject to the state's 2023 ADU preemption statute, House Bill 1337 codified at RCW 36.70A.680 through RCW 36.70A.700. Because Kennewick exceeds the 25,000-population threshold and lies within a fully-planning GMA county (Benton County), it must permit two accessory dwelling units (ADUs) per lot in all areas zoned predominantly for residential use. Local detail is implemented through Title 18 of the Kennewick Municipal Code (Zoning), hosted on Code Publishing at https://www.codepublishing.com/WA/Kennewick/.
Kennewick WA ADU Rules (HB 1337 / RCW 36.70A.681; KMC Title 18 Zoning)
Few RestrictionsADU Permits
An ADU in Kennewick requires permits from two municipal tracks: a zoning clearance confirming the ADU complies with KMC Title 18 as updated for HB 1337 compliance, and a building permit under the Washington State Building Code at WAC 51-51. Because Washington HB 1337 (RCW 36.70A.681) preempts discretionary review for compliant ADUs, Kennewick must process most ADU applications ministerially within the time frames imposed by RCW 36.70B.080 (local project review). The Kennewick Planning Division and Building Division handle the application. The Kennewick Municipal Code is on Code Publishing at https://www.codepublishing.com/WA/Kennewick/.
Kennewick WA ADU Permits (KMC Title 18; HB 1337 60-Day Review Standard)
Few RestrictionsADU Impact Fees
Washington HB 1337 at RCW 36.70A.696 caps impact fees for accessory dwelling units at 50 percent of the impact fee charged for an equivalent single-family residence. The underlying GMA impact-fee authority is at RCW 82.02.050 through 82.02.110, which authorizes counties, cities, and towns planning under the Growth Management Act to impose impact fees for public streets and roads, parks and recreation, schools, and fire protection. Kennewick (subject to the GMA in Benton County) may charge transportation, parks, and school impact fees through KMC and the local fee schedule, but all ADU fees are subject to the 50 percent statutory cap. School impact fees flow to the Kennewick School District under interlocal agreement.
Kennewick WA ADU Impact Fees (RCW 36.70A.696 50% Cap; RCW 82.02 GMA Impact Fee Authority)
Few RestrictionsShed Rules
Sheds in Kennewick are regulated through two layers: (1) Kennewick Municipal Code Title 18 (Zoning) setting accessory-structure dimensional standards by district — typically rear-yard location, district-specific setbacks, and a maximum height around 15 feet; and (2) the Washington State Building Code at WAC 51-51, adopting the 2021 International Residential Code, which under IRC R105.2 exempts one-story detached accessory structures of 200 square feet or less from building permit requirements but does not waive zoning compliance. A zoning permit from the Kennewick Planning Division is generally still required even when a building permit is not.
Kennewick WA Shed Rules (KMC Title 18 Accessory Structures; IRC R105.2 Permit Exemption)
Some RestrictionsGarage Conversions
Converting a Kennewick garage into habitable space requires both (1) zoning approval under KMC Title 18 for the change of use, since the converted area no longer functions as accessory parking and may trigger off-street parking minimums or ADU classification under HB 1337; and (2) a building permit under the Washington State Building Code at WAC 51-51 (2021 IRC). Conversions must meet IRC Chapter 3 requirements for habitable space including R310 emergency escape and rescue openings, R305 ceiling height, R314 smoke alarms, and R315 carbon monoxide alarms. RCW 19.27.180 governs residential sprinkler requirements; one- and two-family dwellings are generally exempt from automatic sprinkler retrofit on conversion.
Kennewick WA Garage Conversions (KMC Title 18 Change-of-Use; IRC R310 Egress; RCW 19.27.180)
Some RestrictionsLooking for Benton County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Kennewick city rules.
Accessory Structures in Benton County →