Skip to main content
CityRuleLookup
Accessory Structures

Accessory Structures in Kennewick, WA: What Residents Actually Need to Know

By CityRuleLookup Editorial Team

If you live in Kennewick or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Kennewick has 2 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

ADU Rules

Kennewick allows two accessory dwelling units per lot in every residential zone, each capped at 1,100 square feet and 24 feet in height if detached, under KMC 18.12.020: a local rule that already tracks Washington's 2023 HB 1337 statewide floor.

Key details: ADUs per lot: Two, any configuration. Max floor area: 1,100 sq ft each. Detached height cap: 24 feet. Parking required: 1 space per ADU. Impact fees: 50% of primary dwelling's.

Building an ADU over 1,100 square feet, over the height cap, or without the required off-street parking space is a zoning violation subject to Planning Division code enforcement and permit denial.

Shed & Carport Rules

In Kennewick's R and HMU districts, detached sheds and accessory buildings must sit at least 5 feet from side and rear lot lines, 10 feet from the main house, and no taller than 20 feet.

Key details: Side/rear setback: 5 feet minimum. Separation from house: 10 feet, or 4 feet if IBC-built. Height cap: 20 feet in R and HMU. Districts covered: All R districts and HMU.

Building a shed closer than the required setback, exceeding 20 feet in height outside the exempt districts, or placing it within ten feet of a dwelling window violates KMC 18.27.030 and can force removal or relocation.

The Bottom Line

Kennewick's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Kennewick is broadly strict or permissive.

These rules come from Kennewick's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.