ADU (accessory dwelling unit) Rules in Kittitas County, WA: What to Check
Kittitas County ADU planning: rural administrative permits, the 1,500-square-foot limit, separate urban rules, water, septic, and access.
Start a Kittitas County ADU project by identifying the permitting jurisdiction and zoning. An Ellensburg or Cle Elum mailing address can describe a city property, an unincorporated urban-growth-area property, or rural land. Those are different review paths.
An ADU is a secondary, self-contained dwelling on the same lot as a primary home. It is different from the county’s separately defined accessory living quarters and special care dwelling. Mixing those categories can produce the wrong size, occupancy, or permit advice.
Rural county rules
For zones governed by the rural/resource use table in KCC 17.15.060, footnote 27 sets these ADU conditions:
- A parcel of at least three acres and no more than one ADU per lot.
- An ADU no larger than 1,500 square feet.
- The setbacks of the applicable zone.
- Approved potable water and sewage disposal, including an adequate legal water supply.
- Additional off-street parking and the same driveway as the primary dwelling.
- No ADU on a lot that already has accessory living quarters or a special care dwelling.
- An administrative permit. The ADU entry is not a blanket conditional-use requirement.
The use table must also allow the ADU in the parcel’s zone, and overlay restrictions can apply. These rural figures are not a countywide standard for every urban growth area, LAMIRD, or incorporated city.
Urban and other county areas
Title 17 has separate provisions for the Ellensburg urban growth area, other urban growth areas, and limited areas of more intensive rural development. Confirm which table governs before using a unit count, lot minimum, height, or parking figure. For state context, see our Washington ADU guide.
Owner occupancy and rental plans
Rural ADU footnote 27 does not state an owner-occupancy condition or a size limit based on a percentage of the main house. The neighboring rule for accessory living quarters does. Do not apply that separate category’s restrictions to an ADU.
Tell the reviewer whether the home will house family, a long-term tenant, or short-term guests. Confirm the applicable rental rules and any title restrictions before relying on rental income. ADU approval itself does not approve a land division or separate sale.
Water, septic, and delivery
A well’s presence does not establish that an additional dwelling has an adequate legal water supply. Obtain the water records and health review early. For septic, compare the proposed bedrooms with the approved system and reserve area; for sewer, obtain the provider’s connection requirements.
Wolf also checks the delivery route, shared driveway, staging space, foundation location, and any crane needs. Factory construction still requires approval for the site’s placement, utilities, and foundation.
For pass delivery, snow, and how Kittitas compares with other mountain counties, see mountain cabins and ADUs in the Cascades.
Start with your parcel
Have the address or parcel number, existing-home information, intended use, and available well/septic records ready. We use those details to identify the right review path and compare the current models.
Request a free Wolf property evaluation.
General planning information. Confirm current requirements, fees, and parcel eligibility with the county or city before committing to a design.
Sources
Requirements change, so check the current forms and rules with your jurisdiction before you file. This is general information, not legal advice.