Walla Walla County, WA Accessory Structures: ADU Owner Occupancy (2026)

Walla Walla County Code Section 17.08.015 sets nine conditions an accessory dwelling unit must satisfy before Community Development will issue a building permit for it in unincorporated Walla Walla County. Condition J is the owner-occupancy rule: either the primary residence or the accessory dwelling unit must be occupied by an owner of the property for at least six months out of a year, and at no time can the owner receive rent for whichever dwelling counts as the owner-occupied unit. The rule works alongside the rest of Section 17.08.015: the primary residence must be at least 800 square feet before an ADU is allowed, the ADU itself is capped at 1,100 square feet or 50 percent of the primary residence's square footage (excluding garage and other nonliving space), whichever is less, and only one ADU is permitted per lot.

The ADU must also depend on the primary residence, sharing at least four of six listed features such as road access, septic, water, utility meters, yard, or parking area. Because the code bars rent on the owner-occupied side while separately allowing the ADU to be rented under condition K, most owners in the unincorporated county satisfy J by living in the primary residence rent-free and renting out the ADU. Walla Walla County's Community Development Department, which handles building permits, planning, and code enforcement for the unincorporated area, reviews owner-occupancy compliance at the building permit stage and can act on complaints afterward.

This owner-occupancy condition applies only outside the city limits of Walla Walla, College Place, Waitsburg, and Prescott, each of which regulates ADUs under its own municipal code.